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Provide installable man pages

Browse source 
make docs: generate Markdown and man pages in doc/
make install-docs: install man pages to be usable directly

Docs are generated from the ezdoc files in doc/src/.
This commit is contained in:
Loïc Hoguin 2014-07-06 13:10:35 +02:00
parent 1a71a733c3
commit 078d686a0a
80 changed files with 2419 additions and 2512 deletions
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3
.gitignore vendored
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@ -2,6 +2,9 @@
.erlang.mk.packages.* .erlang.mk.packages.*
_rel _rel
deps deps
doc/man3
doc/man7
doc/markdown
ebin ebin
logs logs
relx relx

52
Makefile
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@ -24,3 +24,55 @@ dep_gun = pkg://gun master
# Standard targets. # Standard targets.
include erlang.mk include erlang.mk
# Documentation.
dep_ezdoc = https://github.com/ninenines/ezdoc master
$(eval $(call dep_target,ezdoc))
build-doc-deps: $(DEPS_DIR)/ezdoc
$(MAKE) -C $(DEPS_DIR)/ezdoc
define ezdoc_script
io:format("Building manual~n"),
[begin
AST = ezdoc:parse_file(F),
BF = filename:rootname(filename:basename(F)),
io:format(" ~s~n", [BF]),
file:write_file("doc/markdown/manual/" ++ BF ++ ".md", ezdoc_markdown:export(AST)),
case BF of
"cowboy" ++ _ when BF =/= "cowboy_app" ->
file:write_file("doc/man3/" ++ BF ++ ".3", ezdoc_man:export(3, AST));
_ when BF =/= "index" ->
file:write_file("doc/man7/" ++ BF ++ ".7", ezdoc_man:export(7, AST));
_ ->
ok
end
end || F <- filelib:wildcard("doc/src/manual/*.ezdoc")],
io:format("Building guide~n"),
[begin
AST = ezdoc:parse_file(F),
BF = filename:rootname(filename:basename(F)),
io:format(" ~s~n", [BF]),
file:write_file("doc/markdown/guide/" ++ BF ++ ".md", ezdoc_markdown:export(AST))
end || F <- filelib:wildcard("doc/src/guide/*.ezdoc")],
io:format("Done.~n"),
init:stop().
endef
export ezdoc_script
docs: clean-docs build-doc-deps
@mkdir -p doc/man3 doc/man7 doc/markdown/guide doc/markdown/manual
$(gen_verbose) erl -noinput -pa ebin deps/ezdoc/ebin -eval "$$ezdoc_script"
@gzip doc/man3/*.3 doc/man7/*.7
@cp doc/src/guide/*.png doc/markdown/guide
clean-docs:
$(gen_verbose) rm -rf doc/man3 doc/man7 doc/markdown
MAN_INSTALL_PATH ?= /usr/local/share/man
install-docs:
mkdir -p $(MAN_INSTALL_PATH)/man3/ $(MAN_INSTALL_PATH)/man7/
install -g 0 -o 0 -m 0644 doc/man3/*.gz $(MAN_INSTALL_PATH)/man3/
install -g 0 -o 0 -m 0644 doc/man7/*.gz $(MAN_INSTALL_PATH)/man7/

22
README.md
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@ -27,15 +27,23 @@ The SPDY implementation was sponsored by
The project is currently sponsored by The project is currently sponsored by
[Kato.im](https://kato.im). [Kato.im](https://kato.im).
Getting Started Online documentation
--------------- --------------------
* [Read the guide](http://ninenines.eu/docs/en/cowboy/HEAD/guide) * [User guide](http://ninenines.eu/docs/en/cowboy/HEAD/guide)
* [Check the manual](http://ninenines.eu/docs/en/cowboy/HEAD/manual) * [Function reference](http://ninenines.eu/docs/en/cowboy/HEAD/manual)
* Look at the examples in the `examples/` directory
Support Offline documentation
------- ---------------------
* While still online, run `make docs`
* Function reference man pages available in `doc/man3/` and `doc/man7/`
* Run `make install-docs` to install man pages on your system
* Full documentation in Markdown available in `doc/markdown/`
* Examples available in `examples/`
Getting help
------------
* Official IRC Channel: #ninenines on irc.freenode.net * Official IRC Channel: #ninenines on irc.freenode.net
* [Mailing Lists](http://lists.ninenines.eu) * [Mailing Lists](http://lists.ninenines.eu)

15
guide/architecture.md → doc/src/guide/architecture.ezdoc
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@ -1,13 +1,11 @@
Architecture ::: Architecture
============
Cowboy is a lightweight HTTP server. Cowboy is a lightweight HTTP server.
It is built on top of Ranch. Please see the Ranch guide for more It is built on top of Ranch. Please see the Ranch guide for more
information. information.
One process per connection :: One process per connection
--------------------------
It uses only one process per connection. The process where your It uses only one process per connection. The process where your
code runs is the process controlling the socket. Using one process code runs is the process controlling the socket. Using one process
@ -22,8 +20,7 @@ up before terminating the handling of the current request. This may
include cleaning up the process dictionary, timers, monitoring and include cleaning up the process dictionary, timers, monitoring and
more. more.
Binaries :: Binaries
--------
It uses binaries. Binaries are more efficient than lists for It uses binaries. Binaries are more efficient than lists for
representing strings because they take less memory space. Processing representing strings because they take less memory space. Processing
@ -31,16 +28,14 @@ performance can vary depending on the operation. Binaries are known
for generally getting a great boost if the code is compiled natively. for generally getting a great boost if the code is compiled natively.
Please see the HiPE documentation for more details. Please see the HiPE documentation for more details.
Date header :: Date header
-----------
Because querying for the current date and time can be expensive, Because querying for the current date and time can be expensive,
Cowboy generates one `Date` header value every second, shares it Cowboy generates one `Date` header value every second, shares it
to all other processes, which then simply copy it in the response. to all other processes, which then simply copy it in the response.
This allows compliance with HTTP/1.1 with no actual performance loss. This allows compliance with HTTP/1.1 with no actual performance loss.
Max connections :: Max connections
---------------
By default the maximum number of active connections is set to a By default the maximum number of active connections is set to a
generally accepted big enough number. This is meant to prevent having generally accepted big enough number. This is meant to prevent having

12
guide/broken_clients.md → doc/src/guide/broken_clients.ezdoc
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@ -1,5 +1,4 @@
Dealing with broken clients ::: Dealing with broken clients
===========================
There exists a very large number of implementations for the There exists a very large number of implementations for the
HTTP protocol. Most widely used clients, like browsers, HTTP protocol. Most widely used clients, like browsers,
@ -16,8 +15,7 @@ That means clients that ignore the HTTP standard completely
may fail to understand Cowboy's responses. There are of may fail to understand Cowboy's responses. There are of
course workarounds. This chapter aims to cover them. course workarounds. This chapter aims to cover them.
Lowercase headers :: Lowercase headers
-----------------
Cowboy converts all headers it receives to lowercase, and Cowboy converts all headers it receives to lowercase, and
similarly sends back headers all in lowercase. Some broken similarly sends back headers all in lowercase. Some broken
@ -39,8 +37,7 @@ because the specification explicitly says all headers are
lowercase, unlike HTTP which allows any case but treats lowercase, unlike HTTP which allows any case but treats
them as case insensitive. them as case insensitive.
Camel-case headers :: Camel-case headers
------------------
Sometimes it is desirable to keep the actual case used by Sometimes it is desirable to keep the actual case used by
clients, for example when acting as a proxy between two broken clients, for example when acting as a proxy between two broken
@ -48,8 +45,7 @@ implementations. There is no easy solution for this other than
forking the project and editing the `cowboy_protocol` file forking the project and editing the `cowboy_protocol` file
directly. directly.
Chunked transfer-encoding :: Chunked transfer-encoding
-------------------------
Sometimes an HTTP client advertises itself as HTTP/1.1 but Sometimes an HTTP client advertises itself as HTTP/1.1 but
does not support chunked transfer-encoding. This is invalid does not support chunked transfer-encoding. This is invalid

9
guide/cookies.md → doc/src/guide/cookies.ezdoc
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@ -1,5 +1,4 @@
Using cookies ::: Using cookies
=============
Cookies are a mechanism allowing applications to maintain Cookies are a mechanism allowing applications to maintain
state on top of the stateless HTTP protocol. state on top of the stateless HTTP protocol.
@ -49,8 +48,7 @@ that run from HTTPS webpages.
Finally, cookies can be restricted to HTTP and HTTPS requests, Finally, cookies can be restricted to HTTP and HTTPS requests,
essentially disabling their access from client-side scripts. essentially disabling their access from client-side scripts.
Setting cookies :: Setting cookies
---------------
By default, cookies you set are defined for the session. By default, cookies you set are defined for the session.
@ -112,8 +110,7 @@ Req2 = cowboy_req:set_resp_cookie(<<"sessionid">>, SessionID, [
Cookies may also be set client-side, for example using Cookies may also be set client-side, for example using
Javascript. Javascript.
Reading cookies :: Reading cookies
---------------
As we said, the client sends cookies with every request. As we said, the client sends cookies with every request.
But unlike the server, the client only sends the cookie But unlike the server, the client only sends the cookie

13
guide/erlang_beginners.md → doc/src/guide/erlang_beginners.ezdoc
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@ -1,5 +1,4 @@
Erlang for beginners ::: Erlang for beginners
====================
Chances are you are interested in using Cowboy, but have Chances are you are interested in using Cowboy, but have
no idea how to write an Erlang program. Fear not! This no idea how to write an Erlang program. Fear not! This
@ -9,11 +8,10 @@ We recommend two books for beginners. You should read them
both at some point, as they cover Erlang from two entirely both at some point, as they cover Erlang from two entirely
different perspectives. different perspectives.
Learn You Some Erlang for Great Good! :: Learn You Some Erlang for Great Good!
-------------------------------------
The quickest way to get started with Erlang is by reading The quickest way to get started with Erlang is by reading
a book with the funny name of [LYSE](http://learnyousomeerlang.com), a book with the funny name of ^"LYSE^http://learnyousomeerlang.com^,
as we affectionately call it. as we affectionately call it.
It will get right into the syntax and quickly answer the questions It will get right into the syntax and quickly answer the questions
@ -24,13 +22,12 @@ You can read an early version of the book online for free,
but you really should buy the much more refined paper and but you really should buy the much more refined paper and
ebook versions. ebook versions.
Programming Erlang :: Programming Erlang
------------------
After writing some code, you will probably want to understand After writing some code, you will probably want to understand
the very concepts that make Erlang what it is today. These the very concepts that make Erlang what it is today. These
are best explained by Joe Armstrong, the godfather of Erlang, are best explained by Joe Armstrong, the godfather of Erlang,
in his book [Programming Erlang](http://pragprog.com/book/jaerlang2/programming-erlang). in his book ^"Programming Erlang^http://pragprog.com/book/jaerlang2/programming-erlang^.
Instead of going into every single details of the language, Instead of going into every single details of the language,
Joe focuses on the central concepts behind Erlang, and shows Joe focuses on the central concepts behind Erlang, and shows

18
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@ -1,8 +1,6 @@
Erlang and the Web ::: Erlang and the Web
==================
The Web is concurrent :: The Web is concurrent
---------------------
When you access a website there is little concurrency When you access a website there is little concurrency
involved. A few connections are opened and requests involved. A few connections are opened and requests
@ -55,8 +53,7 @@ will also connect to various applications on the Internet.
Only Erlang is prepared to deal with what's coming. Only Erlang is prepared to deal with what's coming.
The Web is soft real time :: The Web is soft real time
-------------------------
What does soft real time mean, you ask? It means we want the What does soft real time mean, you ask? It means we want the
operations done as quickly as possible, and in the case of operations done as quickly as possible, and in the case of
@ -85,8 +82,7 @@ can guarantee stable low latency of operations.
Erlang provides the guarantees that the soft real time Web Erlang provides the guarantees that the soft real time Web
requires. requires.
The Web is asynchronous :: The Web is asynchronous
-----------------------
Long ago, the Web was synchronous because HTTP was synchronous. Long ago, the Web was synchronous because HTTP was synchronous.
You fired a request, and then waited for a response. Not anymore. You fired a request, and then waited for a response. Not anymore.
@ -118,8 +114,7 @@ Erlang is by nature asynchronous and really good at it thanks to the
great engineering that has been done in the VM over the years. It's great engineering that has been done in the VM over the years. It's
only natural that it's so good at dealing with the asynchronous Web. only natural that it's so good at dealing with the asynchronous Web.
The Web is omnipresent :: The Web is omnipresent
----------------------
The Web has taken a very important part of our lives. We're The Web has taken a very important part of our lives. We're
connected at all times, when we're on our phone, using our computer, connected at all times, when we're on our phone, using our computer,
@ -172,8 +167,7 @@ down, or even a data center entirely.
Fault tolerance and distribution are important today, and will be Fault tolerance and distribution are important today, and will be
vital in the future of the Web. Erlang is ready. vital in the future of the Web. Erlang is ready.
Erlang is the ideal platform for the Web :: Erlang is the ideal platform for the Web
----------------------------------------
Erlang provides all the important features that the Web requires Erlang provides all the important features that the Web requires
or will require in the near future. Erlang is a perfect match or will require in the near future. Erlang is a perfect match

34
guide/getting_started.md → doc/src/guide/getting_started.ezdoc
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@ -1,5 +1,4 @@
Getting started ::: Getting started
===============
Erlang is more than a language, it is also an operating system Erlang is more than a language, it is also an operating system
for your applications. Erlang developers rarely write standalone for your applications. Erlang developers rarely write standalone
@ -13,14 +12,13 @@ Cowboy, writing your first application and generating your first
release. At the end of this chapter you should know everything release. At the end of this chapter you should know everything
you need to push your first Cowboy application to production. you need to push your first Cowboy application to production.
Application skeleton :: Application skeleton
--------------------
Let's start by creating this application. We will simply call it Let's start by creating this application. We will simply call it
`hello_erlang`. This application will have the following directory `hello_erlang`. This application will have the following directory
structure: structure:
``` ``` bash
hello_erlang/ hello_erlang/
src/ src/
hello_erlang.app.src hello_erlang.app.src
@ -35,7 +33,7 @@ hello_erlang/
Once the release is generated, we will also have the following Once the release is generated, we will also have the following
files added: files added:
``` ``` bash
hello_erlang/ hello_erlang/
ebin/ ebin/
hello_erlang.app hello_erlang.app
@ -54,11 +52,11 @@ The `.app` file contains various informations about the application.
It contains its name, a description, a version, a list of modules, It contains its name, a description, a version, a list of modules,
default configuration and more. default configuration and more.
Using a build system like [erlang.mk](https://github.com/extend/erlang.mk), Using a build system like ^"erlang.mk^https://github.com/extend/erlang.mk^,
the list of modules will be included automatically in the `.app` file, the list of modules will be included automatically in the `.app` file,
so you don't need to manually put them in your `.app.src` file. so you don't need to manually put them in your `.app.src` file.
For generating the release, we will use [relx](https://github.com/erlware/relx) For generating the release, we will use ^"relx^https://github.com/erlware/relx
as it is a much simpler alternative to the tool coming with Erlang. as it is a much simpler alternative to the tool coming with Erlang.
First, create the `hello_erlang` directory. It should have the same name First, create the `hello_erlang` directory. It should have the same name
@ -129,8 +127,7 @@ That's not enough however. Since we are building a Cowboy based
application, we also need to initialize Cowboy when we start our application, we also need to initialize Cowboy when we start our
application. application.
Setting up Cowboy :: Setting up Cowboy
-----------------
Cowboy does nothing by default. Cowboy does nothing by default.
@ -145,7 +142,7 @@ Listeners are a group of processes that are used to accept and manage
connections. The processes used specifically for accepting connections connections. The processes used specifically for accepting connections
are called acceptors. The number of acceptor processes is unrelated to are called acceptors. The number of acceptor processes is unrelated to
the maximum number of connections Cowboy can handle. Please refer to the maximum number of connections Cowboy can handle. Please refer to
the [Ranch guide](http://ninenines.eu/docs/en/ranch/HEAD/guide/) the ^"Ranch guide^http://ninenines.eu/docs/en/ranch/HEAD/guide/
for in-depth information. for in-depth information.
Listeners are named. They spawn a given number of acceptors, listen for Listeners are named. They spawn a given number of acceptors, listen for
@ -154,7 +151,7 @@ options to the connection processes. The protocol options must include
the dispatch list for routing requests to handlers. the dispatch list for routing requests to handlers.
The dispatch list is explained in greater details in the The dispatch list is explained in greater details in the
[Routing](routing.md) chapter. For the purpose of this example ^"Routing^routing^ chapter. For the purpose of this example
we will simply map all URLs to our handler `hello_handler`, we will simply map all URLs to our handler `hello_handler`,
using the wildcard `_` for both the hostname and path parts using the wildcard `_` for both the hostname and path parts
of the URL. of the URL.
@ -200,15 +197,14 @@ init([]) ->
Finally, we need to write the code for handling incoming requests. Finally, we need to write the code for handling incoming requests.
Handling HTTP requests :: Handling HTTP requests
----------------------
Cowboy features many kinds of handlers. For this simple example, Cowboy features many kinds of handlers. For this simple example,
we will just use the plain HTTP handler, which has three callback we will just use the plain HTTP handler, which has three callback
functions: `init/3`, `handle/2` and `terminate/3`. You can find more functions: `init/3`, `handle/2` and `terminate/3`. You can find more
information about the arguments and possible return values of these information about the arguments and possible return values of these
callbacks in the callbacks in the
[cowboy_http_handler function reference](http://ninenines.eu/docs/en/cowboy/HEAD/manual/cowboy_http_handler). ^"cowboy_http_handler function reference^http://ninenines.eu/docs/en/cowboy/HEAD/manual/cowboy_http_handler^.
Our handler will only send a friendly hello back to the client. Our handler will only send a friendly hello back to the client.
@ -236,12 +232,11 @@ terminate(_Reason, _Req, _State) ->
The `Req` variable above is the Req object, which allows the developer The `Req` variable above is the Req object, which allows the developer
to obtain information about the request and to perform a reply. to obtain information about the request and to perform a reply.
Its usage is documented in the Its usage is documented in the
[cowboy_req function reference](http://ninenines.eu/docs/en/cowboy/HEAD/manual/cowboy_req). ^"cowboy_req function reference^http://ninenines.eu/docs/en/cowboy/HEAD/manual/cowboy_req^.
The code for our application is ready, so let's build a release! The code for our application is ready, so let's build a release!
Compiling :: Compiling
---------
First we need to download `erlang.mk`. First we need to download `erlang.mk`.
@ -279,8 +274,7 @@ haven't made any typo when creating the previous files.
$ make $ make
``` ```
Generating the release :: Generating the release
----------------------
That's not all however, as we want to create a working release. That's not all however, as we want to create a working release.
For that purpose, we need to create a `relx.config` file. When For that purpose, we need to create a `relx.config` file. When

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@ -1,12 +1,10 @@
Hooks ::: Hooks
=====
Cowboy provides two hooks. `onrequest` is called once the request Cowboy provides two hooks. `onrequest` is called once the request
line and headers have been received. `onresponse` is called just line and headers have been received. `onresponse` is called just
before sending the response. before sending the response.
Onrequest :: Onrequest
---------
The `onrequest` hook is called as soon as Cowboy finishes fetching The `onrequest` hook is called as soon as Cowboy finishes fetching
the request headers. It occurs before any other processing, including the request headers. It occurs before any other processing, including
@ -43,8 +41,7 @@ debug_hook(Req) ->
Make sure to always return the last request object obtained. Make sure to always return the last request object obtained.
Onresponse :: Onresponse
----------
The `onresponse` hook is called right before sending the response The `onresponse` hook is called right before sending the response
to the socket. It can be used for the purposes of logging responses, to the socket. It can be used for the purposes of logging responses,

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@ -1,13 +1,11 @@
Handling plain HTTP requests ::: Handling plain HTTP requests
============================
The simplest way to handle a request is by writing a The simplest way to handle a request is by writing a
plain HTTP handler. It is modeled after Erlang/OTP's plain HTTP handler. It is modeled after Erlang/OTP's
gen_server behaviour, although simplified, as Cowboy gen_server behaviour, although simplified, as Cowboy
will simply call the three callbacks sequentially. will simply call the three callbacks sequentially.
Initialization :: Initialization
--------------
The first callback, `init/3`, is common to all handlers, The first callback, `init/3`, is common to all handlers,
as it is used to identify the type of handler. Plain as it is used to identify the type of handler. Plain
@ -92,8 +90,7 @@ init(_Type, Req, Opts) ->
{ok, Req, #state{lang=Lang}}. {ok, Req, #state{lang=Lang}}.
``` ```
Handling the request :: Handling the request
--------------------
The second callback, `handle/2`, is specific to plain HTTP The second callback, `handle/2`, is specific to plain HTTP
handlers. It's where you, wait for it, handle the request. handlers. It's where you, wait for it, handle the request.
@ -119,8 +116,7 @@ handle(Req, State) ->
{ok, Req2, State}. {ok, Req2, State}.
``` ```
Cleaning up :: Cleaning up
-----------
The third and last callback, `terminate/3`, will most likely The third and last callback, `terminate/3`, will most likely
be empty in your handler. be empty in your handler.

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@ -1,12 +1,10 @@
The life of a request ::: The life of a request
=====================
This chapter explains the different steps a request This chapter explains the different steps a request
goes through until a response is sent, along with goes through until a response is sent, along with
details of the Cowboy implementation. details of the Cowboy implementation.
Request/response :: Request/response
----------------
As you already know, HTTP clients connect to the server and As you already know, HTTP clients connect to the server and
send a request for a resource; the server then sends a send a request for a resource; the server then sends a
@ -20,7 +18,7 @@ add like writing logs.
Requests take the following route in Cowboy: Requests take the following route in Cowboy:
![HTTP request/response flowchart](http_req_resp.png) ^"HTTP request/response flowchart^!http_req_resp.png
This shows the default middlewares, but they may be This shows the default middlewares, but they may be
configured differently in your setup. The dark green configured differently in your setup. The dark green
@ -44,8 +42,7 @@ When a response is sent, you can optionally modify it
or act upon it by enabling the `onresponse` hook. By or act upon it by enabling the `onresponse` hook. By
default the response is sent directly to the client. default the response is sent directly to the client.
And then? :: And then?
---------
Behavior depends on what protocol is in use. Behavior depends on what protocol is in use.
@ -62,8 +59,7 @@ asynchronously on the same connection. Details on what
this means for your application is described in this this means for your application is described in this
chapter. chapter.
Keep-alive (HTTP/1.1) :: Keep-alive (HTTP/1.1)
---------------------
With HTTP/1.1, the connection may be left open for With HTTP/1.1, the connection may be left open for
subsequent requests to come. This mechanism is called subsequent requests to come. This mechanism is called
@ -110,8 +106,7 @@ But it also means you need to clean up if you do have
code with side effects. The `terminate/3` function can code with side effects. The `terminate/3` function can
be used for this purpose. be used for this purpose.
Pipelining (HTTP/1.1) :: Pipelining (HTTP/1.1)
---------------------
While HTTP is designed as a sequential protocol, with While HTTP is designed as a sequential protocol, with
the client sending a request and then waiting for the the client sending a request and then waiting for the
@ -128,8 +123,7 @@ static files for example.
This is handled automatically by the server. This is handled automatically by the server.
Asynchronous requests (SPDY) :: Asynchronous requests (SPDY)
----------------------------
In SPDY, the client can send a request at any time. In SPDY, the client can send a request at any time.
And the server can send a response at any time too. And the server can send a response at any time too.

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@ -0,0 +1,58 @@
::: Cowboy User Guide
The Cowboy User Guide explores the modern Web and how to make
best use of Cowboy for writing powerful web applications.
:: Introducing Cowboy
* ^"Introduction^introduction
* ^"The modern Web^modern_web
* ^"Erlang and the Web^erlang_web
* ^"Erlang for beginners^erlang_beginners
* ^"Getting started^getting_started
:: HTTP
* ^"The life of a request^http_req_life
* ^"Routing^routing
* ^"Handling plain HTTP requests^http_handlers
* ^"The Req object^req
* ^"Reading the request body^req_body
* ^"Sending a response^resp
* ^"Using cookies^cookies
:: Multipart
* ^"Introduction to multipart^multipart_intro
* ^"Multipart requests^multipart_req
:: Static files
* ^"Static handler^static_handlers
:: REST
* ^"REST principles^rest_principles
* ^"Handling REST requests^rest_handlers
* ^"REST flowcharts^rest_flowcharts
* ^"Designing a resource handler^resource_design
:: Websocket
* ^"The Websocket protocol^ws_protocol
* ^"Handling Websocket connections^ws_handlers
:: Server push
* ^"Loop handlers^loop_handlers
:: Pluggable interface
* ^"Middlewares^middlewares
* ^"Protocol upgrades^upgrade_protocol
* ^"Hooks^hooks
:: Internals
* ^"Architecture^architecture
* ^"Dealing with broken clients^broken_clients

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@ -1,5 +1,4 @@
Introduction ::: Introduction
============
Cowboy is a small, fast and modular HTTP server written in Erlang. Cowboy is a small, fast and modular HTTP server written in Erlang.
@ -15,8 +14,7 @@ Cowboy is clean Erlang code. It includes hundreds of tests and its code
is fully compliant with the Dialyzer. It is also well documented and is fully compliant with the Dialyzer. It is also well documented and
features both a Function Reference and a User Guide. features both a Function Reference and a User Guide.
Prerequisites :: Prerequisites
-------------
No Erlang knowledge is required for reading this guide. The reader will No Erlang knowledge is required for reading this guide. The reader will
be introduced to Erlang concepts and redirected to reference material be introduced to Erlang concepts and redirected to reference material
@ -25,8 +23,7 @@ whenever necessary.
Knowledge of the HTTP protocol is recommended but not required, as it Knowledge of the HTTP protocol is recommended but not required, as it
will be detailed throughout the guide. will be detailed throughout the guide.
Supported platforms :: Supported platforms
-------------------
Cowboy is tested and supported on Linux. Cowboy is tested and supported on Linux.
@ -40,8 +37,7 @@ Cowboy is developed for Erlang R15B+.
Cowboy may be compiled on earlier Erlang versions with small source code Cowboy may be compiled on earlier Erlang versions with small source code
modifications but there is no guarantee that it will work as expected. modifications but there is no guarantee that it will work as expected.
Conventions :: Conventions
-----------
In the HTTP protocol, the method name is case sensitive. All standard In the HTTP protocol, the method name is case sensitive. All standard
method names are uppercase. method names are uppercase.

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Loop handlers ::: Loop handlers
=============
Loop handlers are a special kind of HTTP handlers used when the Loop handlers are a special kind of HTTP handlers used when the
response can not be sent right away. The handler enters instead response can not be sent right away. The handler enters instead
@ -25,8 +24,7 @@ and feed these messages to the `info/3` callback. It also features
the `init/3` and `terminate/3` callbacks which work the same as the `init/3` and `terminate/3` callbacks which work the same as
for plain HTTP handlers. for plain HTTP handlers.
Initialization :: Initialization
--------------
The `init/3` function must return a `loop` tuple to enable The `init/3` function must return a `loop` tuple to enable
loop handler behavior. This tuple may optionally contain loop handler behavior. This tuple may optionally contain
@ -49,8 +47,7 @@ init(_Type, Req, _Opts) ->
{loop, Req, undefined_state, 30000, hibernate}. {loop, Req, undefined_state, 30000, hibernate}.
``` ```
Receive loop :: Receive loop
------------
Once initialized, Cowboy will wait for messages to arrive Once initialized, Cowboy will wait for messages to arrive
in the process' mailbox. When a message arrives, Cowboy in the process' mailbox. When a message arrives, Cowboy
@ -84,8 +81,7 @@ This will instruct Cowboy to end the request.
Otherwise a `loop` tuple should be returned. Otherwise a `loop` tuple should be returned.
Streaming loop :: Streaming loop
--------------
Another common case well suited for loop handlers is Another common case well suited for loop handlers is
streaming data received in the form of Erlang messages. streaming data received in the form of Erlang messages.
@ -111,18 +107,16 @@ info(_Msg, Req, State) ->
{loop, Req, State}. {loop, Req, State}.
``` ```
Cleaning up :: Cleaning up
-----------
It is recommended that you set the connection header to It is recommended that you set the connection header to
`close` when replying, as this process may be reused for `close` when replying, as this process may be reused for
a subsequent request. a subsequent request.
Please refer to the [HTTP handlers chapter](http_handlers.md) Please refer to the ^"HTTP handlers chapter^http_handlers
for general instructions about cleaning up. for general instructions about cleaning up.
Timeout :: Timeout
-------
By default Cowboy will not attempt to close the connection By default Cowboy will not attempt to close the connection
if there is no activity from the client. This is not always if there is no activity from the client. This is not always
@ -138,8 +132,7 @@ so there is a configurable limit for it. The default buffer
size is of 5000 bytes, but it may be changed by setting the size is of 5000 bytes, but it may be changed by setting the
`loop_max_buffer` middleware environment value. `loop_max_buffer` middleware environment value.
Hibernate :: Hibernate
---------
To save memory, you may hibernate the process in between To save memory, you may hibernate the process in between
messages received. This is done by returning the atom messages received. This is done by returning the atom

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@ -1,5 +1,4 @@
Middlewares ::: Middlewares
===========
Cowboy delegates the request processing to middleware components. Cowboy delegates the request processing to middleware components.
By default, two middlewares are defined, for the routing and handling By default, two middlewares are defined, for the routing and handling
@ -12,8 +11,7 @@ change the chain of middlewares as needed.
Cowboy will execute all middlewares in the given order, unless one Cowboy will execute all middlewares in the given order, unless one
of them decides to stop processing. of them decides to stop processing.
Usage :: Usage
-----
Middlewares only need to implement a single callback: `execute/2`. Middlewares only need to implement a single callback: `execute/2`.
It is defined in the `cowboy_middleware` behavior. It is defined in the `cowboy_middleware` behavior.
@ -22,6 +20,7 @@ This callback has two arguments. The first is the `Req` object.
The second is the environment. The second is the environment.
Middlewares can return one of four different values: Middlewares can return one of four different values:
* `{ok, Req, Env}` to continue the request processing * `{ok, Req, Env}` to continue the request processing
* `{suspend, Module, Function, Args}` to hibernate * `{suspend, Module, Function, Args}` to hibernate
* `{halt, Req}` to stop processing and move on to the next request * `{halt, Req}` to stop processing and move on to the next request
@ -36,8 +35,7 @@ to send an error back to the socket, the process will just crash. It
is up to the middleware to make sure that a reply is sent if something is up to the middleware to make sure that a reply is sent if something
goes wrong. goes wrong.
Configuration :: Configuration
-------------
The middleware environment is defined as the `env` protocol option. The middleware environment is defined as the `env` protocol option.
In the previous chapters we saw it briefly when we needed to pass In the previous chapters we saw it briefly when we needed to pass
@ -45,6 +43,7 @@ the routing information. It is a list of tuples with the first
element being an atom and the second any Erlang term. element being an atom and the second any Erlang term.
Two values in the environment are reserved: Two values in the environment are reserved:
* `listener` contains the name of the listener * `listener` contains the name of the listener
* `result` contains the result of the processing * `result` contains the result of the processing
@ -58,15 +57,13 @@ environment values to perform.
You can update the environment by calling the `cowboy:set_env/3` You can update the environment by calling the `cowboy:set_env/3`
convenience function, adding or replacing a value in the environment. convenience function, adding or replacing a value in the environment.
Routing middleware :: Routing middleware
------------------
The routing middleware requires the `dispatch` value. If routing The routing middleware requires the `dispatch` value. If routing
succeeds, it will put the handler name and options in the `handler` succeeds, it will put the handler name and options in the `handler`
and `handler_opts` values of the environment, respectively. and `handler_opts` values of the environment, respectively.
Handler middleware :: Handler middleware
------------------
The handler middleware requires the `handler` and `handler_opts` The handler middleware requires the `handler` and `handler_opts`
values. It puts the result of the request handling into `result`. values. It puts the result of the request handling into `result`.

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@ -1,5 +1,4 @@
The modern Web ::: The modern Web
==============
Let's take a look at various technologies from the beginnings Let's take a look at various technologies from the beginnings
of the Web up to this day, and get a preview of what's of the Web up to this day, and get a preview of what's
@ -9,8 +8,7 @@ Cowboy is compatible with all the technology cited in this
chapter except of course HTTP/2.0 which has no implementation chapter except of course HTTP/2.0 which has no implementation
in the wild at the time of writing. in the wild at the time of writing.
The prehistoric Web :: The prehistoric Web
-------------------
HTTP was initially created to serve HTML pages and only HTTP was initially created to serve HTML pages and only
had the GET method for retrieving them. This initial had the GET method for retrieving them. This initial
@ -31,8 +29,7 @@ this.
Most improvements done in recent years focused on reducing Most improvements done in recent years focused on reducing
this load time and reducing the latency of the requests. this load time and reducing the latency of the requests.
HTTP/1.1 :: HTTP/1.1
--------
HTTP/1.1 quickly followed and added a keep-alive mechanism HTTP/1.1 quickly followed and added a keep-alive mechanism
to allow using the same connection for many requests, as to allow using the same connection for many requests, as
@ -50,8 +47,7 @@ clients to perform what is called as pipelining: sending many
requests in a row, and then processing the responses which will requests in a row, and then processing the responses which will
be received in the same order as the requests. be received in the same order as the requests.
REST :: REST
----
The design of HTTP/1.1 was influenced by the REST architectural The design of HTTP/1.1 was influenced by the REST architectural
style. REST, or REpresentational State Transfer, is a style of style. REST, or REpresentational State Transfer, is a style of
@ -76,8 +72,7 @@ to implement RESTful systems.
REST is most often used when designing web application APIs REST is most often used when designing web application APIs
which are generally meant to be used by executable code directly. which are generally meant to be used by executable code directly.
XmlHttpRequest :: XmlHttpRequest
--------------
Also know as AJAX, this technology allows Javascript code running Also know as AJAX, this technology allows Javascript code running
on a web page to perform asynchronous requests to the server. on a web page to perform asynchronous requests to the server.
@ -93,8 +88,7 @@ This is of course still requests initiated by the client,
the server still had no way of pushing data to the client the server still had no way of pushing data to the client
on its own, so new technology appeared to allow that. on its own, so new technology appeared to allow that.
Long-polling :: Long-polling
------------
Polling was a technique used to overcome the fact that the server Polling was a technique used to overcome the fact that the server
cannot push data directly to the client. Therefore the client had cannot push data directly to the client. Therefore the client had
@ -122,8 +116,7 @@ You probably guessed by now that long-polling is a hack, and
like most hacks it can suffer from unforeseen issues, in this like most hacks it can suffer from unforeseen issues, in this
case it doesn't always play well with proxies. case it doesn't always play well with proxies.
HTML5 :: HTML5
-----
HTML5 is, of course, the HTML version after HTML4. But HTML5 HTML5 is, of course, the HTML version after HTML4. But HTML5
emerged to solve a specific problem: dynamic web applications. emerged to solve a specific problem: dynamic web applications.
@ -147,8 +140,7 @@ events from the server.
The solution went on to become HTML5. At the time of writing The solution went on to become HTML5. At the time of writing
it is being standardized. it is being standardized.
EventSource :: EventSource
-----------
EventSource, sometimes also called Server-Sent Events, is a EventSource, sometimes also called Server-Sent Events, is a
technology allowing servers to push data to HTML5 applications. technology allowing servers to push data to HTML5 applications.
@ -167,8 +159,7 @@ UTF-8 encoded text data. Binary data and text data encoded
differently are not allowed by the protocol. A heavier but differently are not allowed by the protocol. A heavier but
more generic approach can be found in Websocket. more generic approach can be found in Websocket.
Websocket :: Websocket
---------
Websocket is a protocol built on top of HTTP/1.1 that provides Websocket is a protocol built on top of HTTP/1.1 that provides
a two-ways communication channel between the client and the a two-ways communication channel between the client and the
@ -188,8 +179,7 @@ A Websocket connection can be used to transfer any kind of data,
small or big, text or binary. Because of this Websocket is small or big, text or binary. Because of this Websocket is
sometimes used for communication between systems. sometimes used for communication between systems.
SPDY :: SPDY
----
SPDY is an attempt to reduce page loading time by opening a SPDY is an attempt to reduce page loading time by opening a
single connection per server, keeping it open for subsequent single connection per server, keeping it open for subsequent
@ -213,8 +203,7 @@ to a SPDY connection seamlessly if the protocol supports it.
The protocol itself has a few shortcomings which are being The protocol itself has a few shortcomings which are being
fixed in HTTP/2.0. fixed in HTTP/2.0.
HTTP/2.0 :: HTTP/2.0
--------
HTTP/2.0 is the long-awaited update to the HTTP/1.1 protocol. HTTP/2.0 is the long-awaited update to the HTTP/1.1 protocol.
It is based on SPDY although a lot has been improved at the It is based on SPDY although a lot has been improved at the

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@ -1,5 +1,4 @@
Introduction to multipart ::: Introduction to multipart
=========================
Multipart originates from MIME, an Internet standard that Multipart originates from MIME, an Internet standard that
extends the format of emails. Multipart messages are a extends the format of emails. Multipart messages are a
@ -19,8 +18,7 @@ Multipart is of course not required for uploading
files, it is only required when you want to do so files, it is only required when you want to do so
through HTML forms. through HTML forms.
Structure :: Structure
---------
A multipart message is a list of parts. Parts may A multipart message is a list of parts. Parts may
contain either a multipart message or a non-multipart contain either a multipart message or a non-multipart
@ -28,8 +26,7 @@ content-type. This allows parts to be arranged in a
tree structure, although this is a rare case as far tree structure, although this is a rare case as far
as the Web is concerned. as the Web is concerned.
Form-data :: Form-data
---------
In the normal case, when a form is submitted, the In the normal case, when a form is submitted, the
browser will use the `application/x-www-form-urlencoded` browser will use the `application/x-www-form-urlencoded`

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@ -1,5 +1,4 @@
Multipart requests ::: Multipart requests
==================
You can read and parse multipart messages using the You can read and parse multipart messages using the
Req object directly. Req object directly.
@ -7,8 +6,7 @@ Req object directly.
Cowboy defines two functions that allows you to get Cowboy defines two functions that allows you to get
information about each part and read their contents. information about each part and read their contents.
Checking the content-type :: Checking the content-type
-------------------------
While there is a variety of multipart messages, the While there is a variety of multipart messages, the
most common on the Web is `multipart/form-data`. It's most common on the Web is `multipart/form-data`. It's
@ -23,8 +21,7 @@ has been sent by parsing the `content-type` header.
= cowboy_req:parse_header(<<"content-type">>, Req). = cowboy_req:parse_header(<<"content-type">>, Req).
``` ```
Reading a multipart message :: Reading a multipart message
---------------------------
To read a message you have to iterate over all its To read a message you have to iterate over all its
parts. Then, for each part, you can inspect its headers parts. Then, for each part, you can inspect its headers
@ -84,8 +81,7 @@ to 8MB. This can of course be overriden. Both functions
can take a second argument, the same list of options that can take a second argument, the same list of options that
will be passed to `cowboy_req:body/2` function. will be passed to `cowboy_req:body/2` function.
Skipping unwanted parts :: Skipping unwanted parts
-----------------------
If you do not want to read a part's body, you can skip it. If you do not want to read a part's body, you can skip it.
Skipping is easy. If you do not call the function to read Skipping is easy. If you do not call the function to read

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@ -1,12 +1,10 @@
The Req object ::: The Req object
==============
The Req object is this variable that you will use to obtain The Req object is this variable that you will use to obtain
information about a request, read the body of the request information about a request, read the body of the request
and send a response. and send a response.
A special variable :: A special variable
------------------
While we call it an "object", it is not an object in the While we call it an "object", it is not an object in the
OOP sense of the term. In fact it is completely opaque OOP sense of the term. In fact it is completely opaque
@ -33,8 +31,7 @@ It also caches the result of operations performed
on the immutable state. That means that some calls on the immutable state. That means that some calls
will give a result much faster when called many times. will give a result much faster when called many times.
Overview of the cowboy_req interface :: Overview of the cowboy_req interface
------------------------------------
The `cowboy_req` interface is divided in four groups The `cowboy_req` interface is divided in four groups
of functions, each having a well defined return type of functions, each having a well defined return type
@ -72,8 +69,7 @@ This chapter covers most of the first group, plus a few other
functions. The next few chapters cover cookies handling, reading functions. The next few chapters cover cookies handling, reading
the request body and sending a response. the request body and sending a response.
Request :: Request
-------
When a client performs a request, it first sends a few required When a client performs a request, it first sends a few required
values. They are sent differently depending on the protocol values. They are sent differently depending on the protocol
@ -109,8 +105,7 @@ Do note however that clients claiming to implement one version
of the protocol does not mean they implement it fully, or even of the protocol does not mean they implement it fully, or even
properly. properly.
Bindings :: Bindings
--------
After routing the request, bindings are available. Bindings After routing the request, bindings are available. Bindings
are these parts of the host or path that you chose to extract are these parts of the host or path that you chose to extract
@ -153,8 +148,7 @@ or get `undefined` otherwise.
{PathInfo, Req2} = cowboy_req:path_info(Req). {PathInfo, Req2} = cowboy_req:path_info(Req).
``` ```
Query string :: Query string
------------
The query string can be obtained directly. The query string can be obtained directly.
@ -181,8 +175,7 @@ Finally, you can obtain all query string values.
{AllValues, Req2} = cowboy_req:qs_vals(Req). {AllValues, Req2} = cowboy_req:qs_vals(Req).
``` ```
Request URL :: Request URL
-----------
You can reconstruct the full URL of the resource. You can reconstruct the full URL of the resource.
@ -197,8 +190,7 @@ path and query string.
{BaseURL, Req2} = cowboy_req:host_url(Req). {BaseURL, Req2} = cowboy_req:host_url(Req).
``` ```
Headers :: Headers
-------
Cowboy allows you to obtain the header values as string, Cowboy allows you to obtain the header values as string,
or parsed into a more meaningful representation. or parsed into a more meaningful representation.
@ -258,8 +250,7 @@ manual. Also note that the result of parsing is cached, so
calling this function multiple times for the same values will calling this function multiple times for the same values will
not have a significant performance impact. not have a significant performance impact.
Meta :: Meta
----
Cowboy will sometimes associate some meta information with Cowboy will sometimes associate some meta information with
the request. Built-in meta values are listed in the manual the request. Built-in meta values are listed in the manual
@ -285,8 +276,7 @@ an `atom()`.
Req2 = cowboy_req:set_meta(the_answer, 42, Req). Req2 = cowboy_req:set_meta(the_answer, 42, Req).
``` ```
Peer :: Peer
----
You can obtain the peer address and port number. This is You can obtain the peer address and port number. This is
not necessarily the actual IP and port of the client, but not necessarily the actual IP and port of the client, but
@ -296,8 +286,7 @@ rather the one of the machine that connected to the server.
{{IP, Port}, Req2} = cowboy_req:peer(Req). {{IP, Port}, Req2} = cowboy_req:peer(Req).
``` ```
Reducing the memory footprint :: Reducing the memory footprint
-----------------------------
When you are done reading information from the request object When you are done reading information from the request object
and know you are not going to access it anymore, for example and know you are not going to access it anymore, for example

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Reading the request body ::: Reading the request body
========================
The Req object also allows you to read the request body. The Req object also allows you to read the request body.
@ -17,8 +16,7 @@ parse in a single call for form urlencoded formats or
multipart. All of these except multipart are covered in multipart. All of these except multipart are covered in
this chapter. Multipart is covered later on in the guide. this chapter. Multipart is covered later on in the guide.
Check for request body :: Check for request body
----------------------
You can check whether a body was sent with the request. You can check whether a body was sent with the request.
@ -33,8 +31,7 @@ Note that it is generally safe to assume that a body is
sent for `POST`, `PUT` and `PATCH` requests, without sent for `POST`, `PUT` and `PATCH` requests, without
having to explicitly check for it. having to explicitly check for it.
Request body length :: Request body length
-------------------
You can obtain the body length if it was sent with the You can obtain the body length if it was sent with the
request. request.
@ -49,8 +46,7 @@ there's a body but no length is given, this means that
the chunked transfer-encoding was used. You can read the chunked transfer-encoding was used. You can read
chunked bodies by using the stream functions. chunked bodies by using the stream functions.
Reading the body :: Reading the body
----------------
You can read the whole body directly in one call. You can read the whole body directly in one call.
@ -78,8 +74,7 @@ If the body is larger than the limit, then Cowboy will return
a `more` tuple instead, allowing you to stream it if you a `more` tuple instead, allowing you to stream it if you
would like to. would like to.
Streaming the body :: Streaming the body
------------------
You can stream the request body by chunks. You can stream the request body by chunks.
@ -102,8 +97,7 @@ body_to_console(Req) ->
You can of course set the `length` option to configure the You can of course set the `length` option to configure the
size of chunks. size of chunks.
Rate of data transmission :: Rate of data transmission
-------------------------
You can control the rate of data transmission by setting You can control the rate of data transmission by setting
options when calling body functions. This applies not only options when calling body functions. This applies not only
@ -116,8 +110,7 @@ to be received from the socket at once, in bytes.
The `read_timeout` option defines the time Cowboy waits The `read_timeout` option defines the time Cowboy waits
before that amount is received, in milliseconds. before that amount is received, in milliseconds.
Transfer and content decoding :: Transfer and content decoding
-----------------------------
Cowboy will by default decode the chunked transfer-encoding Cowboy will by default decode the chunked transfer-encoding
if any. It will not decode any content-encoding by default. if any. It will not decode any content-encoding by default.
@ -136,8 +129,7 @@ The following example shows how to set both options.
]). ]).
``` ```
Reading a form urlencoded body :: Reading a form urlencoded body
------------------------------
You can directly obtain a list of key/value pairs if the You can directly obtain a list of key/value pairs if the
body was sent using the application/x-www-form-urlencoded body was sent using the application/x-www-form-urlencoded

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Designing a resource handler ::: Designing a resource handler
============================
This chapter aims to provide you with a list of questions This chapter aims to provide you with a list of questions
you must answer in order to write a good resource handler. you must answer in order to write a good resource handler.
It is meant to be usable as a step by step guide. It is meant to be usable as a step by step guide.
The service :: The service
-----------
Can the service become unavailable, and when it does, can Can the service become unavailable, and when it does, can
we detect it? For example database connectivity problems we detect it? For example database connectivity problems
@ -19,8 +17,7 @@ more than the standard OPTIONS, HEAD, GET, PUT, POST,
PATCH and DELETE? Are we not using one of those at all? PATCH and DELETE? Are we not using one of those at all?
Implement the `known_methods` callback. Implement the `known_methods` callback.
Type of resource handler :: Type of resource handler
------------------------
Am I writing a handler for a collection of resources, Am I writing a handler for a collection of resources,
or for a single resource? or for a single resource?
@ -29,8 +26,7 @@ The semantics for each of these are quite different.
You should not mix collection and single resource in You should not mix collection and single resource in
the same handler. the same handler.
Collection handler :: Collection handler
------------------
Skip this section if you are not doing a collection. Skip this section if you are not doing a collection.
@ -74,8 +70,7 @@ operation is atomic. The PATCH operation may
be used for such things as reordering; adding, be used for such things as reordering; adding,
modifying or deleting parts of the collection. modifying or deleting parts of the collection.
Single resource handler :: Single resource handler
-----------------------
Skip this section if you are doing a collection. Skip this section if you are doing a collection.
@ -103,8 +98,7 @@ operation is atomic. The PATCH operation may
be used for adding, removing or modifying specific be used for adding, removing or modifying specific
values in the resource. values in the resource.
The resource :: The resource
------------
Following the above discussion, implement the Following the above discussion, implement the
`allowed_methods` callback. `allowed_methods` callback.
@ -131,8 +125,7 @@ Is there any constraints on the length of the resource URI?
For example the URI may be used as a key in storage and may For example the URI may be used as a key in storage and may
have a limit in length. Implement `uri_too_long`. have a limit in length. Implement `uri_too_long`.
Representations :: Representations
---------------
What media types do I provide? If text based, what charsets What media types do I provide? If text based, what charsets
are provided? What languages do I provide? are provided? What languages do I provide?
@ -156,8 +149,7 @@ representation available? Send a list of available
representations in the response body and implement representations in the response body and implement
the `multiple_choices` callback. the `multiple_choices` callback.
Redirections :: Redirections
------------
Do I need to keep track of what resources were deleted? Do I need to keep track of what resources were deleted?
For example you may have a mechanism where moving a For example you may have a mechanism where moving a
@ -169,8 +161,7 @@ it is explicitly temporary, for example due to maintenance,
implement the `moved_temporarily` callback. Otherwise, implement the `moved_temporarily` callback. Otherwise,
implement the `moved_permanently` callback. implement the `moved_permanently` callback.
The request :: The request
-----------
Do we need to perform extra checks to make sure the request Do we need to perform extra checks to make sure the request
is valid? Cowboy will do many checks when receiving the is valid? Cowboy will do many checks when receiving the
@ -185,23 +176,20 @@ to accept? Implement `valid_entity_length`.
Finally, take a look at the sections corresponding to the Finally, take a look at the sections corresponding to the
methods you are implementing. methods you are implementing.
OPTIONS method :: OPTIONS method
--------------
Cowboy by default will send back a list of allowed methods. Cowboy by default will send back a list of allowed methods.
Do I need to add more information to the response? Implement Do I need to add more information to the response? Implement
the `options` method. the `options` method.
GET and HEAD methods :: GET and HEAD methods
--------------------
If you implement the methods GET and/or HEAD, you must If you implement the methods GET and/or HEAD, you must
implement one `ProvideResource` callback for each implement one `ProvideResource` callback for each
content-type returned by the `content_types_provided` content-type returned by the `content_types_provided`
callback. callback.
PUT, POST and PATCH methods :: PUT, POST and PATCH methods
---------------------------
If you implement the methods PUT, POST and/or PATCH, If you implement the methods PUT, POST and/or PATCH,
you must implement the `content_types_accepted` callback, you must implement the `content_types_accepted` callback,
@ -220,8 +208,7 @@ a resource? Do we want to make sure that two updates around
the same time are not cancelling one another? Implement the the same time are not cancelling one another? Implement the
`is_conflict` callback. `is_conflict` callback.
DELETE methods :: DELETE methods
--------------
If you implement the method DELETE, you must implement If you implement the method DELETE, you must implement
the `delete_resource` callback. the `delete_resource` callback.

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Sending a response ::: Sending a response
==================
The Req object also allows you to send a response. The Req object also allows you to send a response.
@ -10,8 +9,7 @@ with its body streamed by chunks of arbitrary size.
You can also set headers or the response body in advance You can also set headers or the response body in advance
and Cowboy will use them when you finally do reply. and Cowboy will use them when you finally do reply.
Reply :: Reply
-----
You can send a reply with no particular headers or body. You can send a reply with no particular headers or body.
Cowboy will make sure to send the mandatory headers with Cowboy will make sure to send the mandatory headers with
@ -66,8 +64,7 @@ Here is the same example but sending HTML this time.
Note that the reply is sent immediately. Note that the reply is sent immediately.
Chunked reply :: Chunked reply
-------------
You can also stream the response body. First, you need to You can also stream the response body. First, you need to
initiate the reply by sending the response status code. initiate the reply by sending the response status code.
@ -98,8 +95,7 @@ ok = cowboy_req:chunk("<body><p>Hats off!</p></body></html>", Req2).
Note that the reply and each chunk following it are sent Note that the reply and each chunk following it are sent
immediately. immediately.
Preset response headers :: Preset response headers
-----------------------
You can define response headers in advance. They will be You can define response headers in advance. They will be
merged into the headers given in the reply call. Headers merged into the headers given in the reply call. Headers
@ -129,8 +125,7 @@ needed. If you do, it will not be sent.
Req2 = cowboy_req:delete_resp_header(<<"allow">>, Req). Req2 = cowboy_req:delete_resp_header(<<"allow">>, Req).
``` ```
Preset response body :: Preset response body
--------------------
You can set the response body in advance. Note that this You can set the response body in advance. Note that this
body will be ignored if you then choose to send a chunked body will be ignored if you then choose to send a chunked
@ -180,8 +175,7 @@ end,
Req2 = cowboy_req:set_resp_body_fun(F, Req). Req2 = cowboy_req:set_resp_body_fun(F, Req).
``` ```
Sending files :: Sending files
-------------
You can send files directly from disk without having to You can send files directly from disk without having to
read them. Cowboy will use the `sendfile` syscall when read them. Cowboy will use the `sendfile` syscall when

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REST flowcharts ::: REST flowcharts
===============
This chapter will explain the REST handler state machine through This chapter will explain the REST handler state machine through
a number of different diagrams. a number of different diagrams.
@ -18,12 +17,11 @@ indicate a response. Other squares may be either a callback or a
question answered by Cowboy itself. Green arrows tend to indicate question answered by Cowboy itself. Green arrows tend to indicate
the default behavior if the callback is undefined. the default behavior if the callback is undefined.
Start :: Start
-----
All requests start from here. All requests start from here.
![REST starting flowchart](rest_start.png) ^"REST starting flowchart^!rest_start.png
A series of callbacks are called in succession to perform A series of callbacks are called in succession to perform
a general checkup of the service, the request line and a general checkup of the service, the request line and
@ -50,12 +48,11 @@ This diagram is immediately followed by either the
"OPTIONS method" diagram when the request method is "OPTIONS method" diagram when the request method is
OPTIONS, or the "Content negotiation" diagram otherwise. OPTIONS, or the "Content negotiation" diagram otherwise.
OPTIONS method :: OPTIONS method
--------------
This diagram only applies to OPTIONS requests. This diagram only applies to OPTIONS requests.
![REST OPTIONS method flowchart](rest_options.png) ^"REST OPTIONS method flowchart^!rest_options.png
The `options` callback may be used to add information The `options` callback may be used to add information
about the resource, such as media types or languages about the resource, such as media types or languages
@ -67,14 +64,13 @@ If the `options` callback is not defined, Cowboy will
send a response containing the list of allowed methods send a response containing the list of allowed methods
by default. by default.
Content negotiation :: Content negotiation
-------------------
This diagram applies to all request methods other than This diagram applies to all request methods other than
OPTIONS. It is executed right after the "Start" diagram OPTIONS. It is executed right after the "Start" diagram
is completed. is completed.
![REST content negotiation flowchart](rest_conneg.png) ^"REST content negotiation flowchart^!rest_conneg.png
The purpose of these steps is to determine an appropriate The purpose of these steps is to determine an appropriate
representation to be sent back to the client. representation to be sent back to the client.
@ -109,15 +105,14 @@ the "PUT, POST and PATCH methods" diagram,
or the "DELETE method" diagram, depending on the or the "DELETE method" diagram, depending on the
method. method.
GET and HEAD methods :: GET and HEAD methods
--------------------
This diagram only applies to GET and HEAD requests. This diagram only applies to GET and HEAD requests.
For a description of the `cond` step, please see For a description of the `cond` step, please see
the "Conditional requests" diagram. the "Conditional requests" diagram.
![REST GET/HEAD methods flowchart](rest_get_head.png) ^"REST GET/HEAD methods flowchart^!rest_get_head.png
When the resource exists, and the conditional steps When the resource exists, and the conditional steps
succeed, the resource can be retrieved. succeed, the resource can be retrieved.
@ -139,15 +134,14 @@ The `moved_permanently` and `moved_temporarily` callbacks
must return the new location of the resource if it was in must return the new location of the resource if it was in
fact moved. fact moved.
PUT, POST and PATCH methods :: PUT, POST and PATCH methods
---------------------------
This diagram only applies to PUT, POST and PATCH requests. This diagram only applies to PUT, POST and PATCH requests.
For a description of the `cond` step, please see For a description of the `cond` step, please see
the "Conditional requests" diagram. the "Conditional requests" diagram.
![REST PUT/POST/PATCH methods flowchart](rest_put_post_patch.png) ^"REST PUT/POST/PATCH methods flowchart^!rest_put_post_patch.png
When the resource exists, first the conditional steps When the resource exists, first the conditional steps
are executed. When that succeeds, and the method is PUT, are executed. When that succeeds, and the method is PUT,
@ -194,15 +188,14 @@ on whether a resource has been created, rather than
modified, and on the availability of a location header modified, and on the availability of a location header
or a body in the response. or a body in the response.
DELETE method :: DELETE method
-------------
This diagram only applies to DELETE requests. This diagram only applies to DELETE requests.
For a description of the `cond` step, please see For a description of the `cond` step, please see
the "Conditional requests" diagram. the "Conditional requests" diagram.
![REST DELETE method flowchart](rest_delete.png) ^"REST DELETE method flowchart^!rest_delete.png
When the resource exists, and the conditional steps When the resource exists, and the conditional steps
succeed, the resource can be deleted. succeed, the resource can be deleted.
@ -234,14 +227,13 @@ The `moved_permanently` and `moved_temporarily` callbacks
must return the new location of the resource if it was in must return the new location of the resource if it was in
fact moved. fact moved.
Conditional requests :: Conditional requests
--------------------
This diagram applies to all request methods other than This diagram applies to all request methods other than
OPTIONS. It is executed right after the `resource_exists` OPTIONS. It is executed right after the `resource_exists`
callback, when the resource exists. callback, when the resource exists.
![REST conditional requests flowchart](rest_cond.png) ^"REST conditional requests flowchart^!rest_cond.png
A request becomes conditional when it includes either of A request becomes conditional when it includes either of
the if-match header; the if-unmodified-since header; the the if-match header; the if-unmodified-since header; the

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REST handlers ::: REST handlers
=============
REST is implemented in Cowboy as a protocol upgrade. Once upgraded, REST is implemented in Cowboy as a protocol upgrade. Once upgraded,
the request is handled as a state machine with many optional callbacks the request is handled as a state machine with many optional callbacks
@ -7,8 +6,7 @@ describing the resource and modifying the machine's behavior.
The REST handler is the recommended way to handle requests. The REST handler is the recommended way to handle requests.
Initialization :: Initialization
--------------
First, the `init/3` callback is called. This callback is common First, the `init/3` callback is called. This callback is common
to all handlers. To use REST for the current request, this function to all handlers. To use REST for the current request, this function
@ -23,8 +21,7 @@ Cowboy will then switch to the REST protocol and start executing
the state machine, starting from `rest_init/2` if it's defined, the state machine, starting from `rest_init/2` if it's defined,
and ending with `rest_terminate/2` also if defined. and ending with `rest_terminate/2` also if defined.
Methods :: Methods
-------
The REST component has code for handling the following HTTP methods: The REST component has code for handling the following HTTP methods:
HEAD, GET, POST, PATCH, PUT, DELETE and OPTIONS. HEAD, GET, POST, PATCH, PUT, DELETE and OPTIONS.
@ -32,8 +29,7 @@ HEAD, GET, POST, PATCH, PUT, DELETE and OPTIONS.
Other methods can be accepted, however they have no specific callback Other methods can be accepted, however they have no specific callback
defined for them at this time. defined for them at this time.
Callbacks :: Callbacks
---------
All callbacks are optional. Some may become mandatory depending All callbacks are optional. Some may become mandatory depending
on what other defined callbacks return. The various flowcharts on what other defined callbacks return. The various flowcharts
@ -63,39 +59,39 @@ All callbacks can also return `{halt, Req, State}` to stop execution
of the request, at which point `rest_terminate/2` will be called. of the request, at which point `rest_terminate/2` will be called.
In the following table, "skip" means the callback is entirely skipped In the following table, "skip" means the callback is entirely skipped
if it is undefined, moving directly to the next step. Similarly, an if it is undefined, moving directly to the next step. Similarly,
empty column means there is no default value for this callback. "none" means there is no default value for this callback.
| Callback name | Default value | || Callback name Default value
| ---------------------- | ------------------------- | |
| allowed_methods | `[<<"GET">>, <<"HEAD">>, <<"OPTIONS">>]` | | allowed_methods `[<<"GET">>, <<"HEAD">>, <<"OPTIONS">>]`
| allow_missing_post | `true` | | allow_missing_post `true`
| charsets_provided | skip | | charsets_provided skip
| content_types_accepted | | | content_types_accepted none
| content_types_provided | `[{{<<"text">>, <<"html">>, '*'}, to_html}] ` | | content_types_provided `[{{<<"text">>, <<"html">>, '*'}, to_html}] `
| delete_completed | `true` | | delete_completed `true`
| delete_resource | `false` | | delete_resource `false`
| expires | `undefined` | | expires `undefined`
| forbidden | `false` | | forbidden `false`
| generate_etag | `undefined` | | generate_etag `undefined`
| is_authorized | `true` | | is_authorized `true`
| is_conflict | `false` | | is_conflict `false`
| known_content_type | `true` | | known_content_type `true`
| known_methods | `[<<"GET">>, <<"HEAD">>, <<"POST">>, <<"PUT">>, <<"PATCH">>, <<"DELETE">>, <<"OPTIONS">>]` | | known_methods `[<<"GET">>, <<"HEAD">>, <<"POST">>, <<"PUT">>, <<"PATCH">>, <<"DELETE">>, <<"OPTIONS">>]`
| languages_provided | skip | | languages_provided skip
| last_modified | `undefined` | | last_modified `undefined`
| malformed_request | `false` | | malformed_request `false`
| moved_permanently | `false` | | moved_permanently `false`
| moved_temporarily | `false` | | moved_temporarily `false`
| multiple_choices | `false` | | multiple_choices `false`
| options | `ok` | | options `ok`
| previously_existed | `false` | | previously_existed `false`
| resource_exists | `true` | | resource_exists `true`
| service_available | `true` | | service_available `true`
| uri_too_long | `false` | | uri_too_long `false`
| valid_content_headers | `true` | | valid_content_headers `true`
| valid_entity_length | `true` | | valid_entity_length `true`
| variances | `[]` | | variances `[]`
As you can see, Cowboy tries to move on with the request whenever As you can see, Cowboy tries to move on with the request whenever
possible by using well thought out default values. possible by using well thought out default values.
@ -108,34 +104,32 @@ each function. For example, `from_html` and `to_html` indicate
in the first case that we're accepting a resource given as HTML, in the first case that we're accepting a resource given as HTML,
and in the second case that we send one as HTML. and in the second case that we send one as HTML.
Meta data :: Meta data
---------
Cowboy will set informative meta values at various points of the Cowboy will set informative meta values at various points of the
execution. You can retrieve them using `cowboy_req:meta/{2,3}`. execution. You can retrieve them using `cowboy_req:meta/{2,3}`.
The values are defined in the following table. The values are defined in the following table.
| Meta key | Details | || Meta key Details
| -----------| ---------------------------------------------------- | |
| media_type | The content-type negotiated for the response entity. | | media_type The content-type negotiated for the response entity.
| language | The language negotiated for the response entity. | | language The language negotiated for the response entity.
| charset | The charset negotiated for the response entity. | | charset The charset negotiated for the response entity.
They can be used to send a proper body with the response to a They can be used to send a proper body with the response to a
request that used a method other than HEAD or GET. request that used a method other than HEAD or GET.
Response headers :: Response headers
----------------
Cowboy will set response headers automatically over the execution Cowboy will set response headers automatically over the execution
of the REST code. They are listed in the following table. of the REST code. They are listed in the following table.
| Header name | Details | || Header name Details
| ---------------- | -------------------------------------------------- | |
| content-language | Language used in the response body | | content-language Language used in the response body
| content-type | Media type and charset of the response body | | content-type Media type and charset of the response body
| etag | Etag of the resource | | etag Etag of the resource
| expires | Expiration date of the resource | | expires Expiration date of the resource
| last-modified | Last modification date for the resource | | last-modified Last modification date for the resource
| location | Relative or absolute URI to the requested resource | | location Relative or absolute URI to the requested resource
| vary | List of headers that may change the representation of the resource | | vary List of headers that may change the representation of the resource

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REST principles ::: REST principles
===============
This chapter will attempt to define the concepts behind REST This chapter will attempt to define the concepts behind REST
and explain what makes a service RESTful. and explain what makes a service RESTful.
@ -11,12 +10,11 @@ and POST methods. That's highly misguided at best.
We will first attempt to define REST and will look at what We will first attempt to define REST and will look at what
it means in the context of HTTP and the Web. it means in the context of HTTP and the Web.
For a more in-depth explanation of REST, you can read For a more in-depth explanation of REST, you can read
[Roy T. Fielding's dissertation](http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm) ^"Roy T. Fielding's dissertation^http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm
as it does a great job explaining where it comes from and as it does a great job explaining where it comes from and
what it achieves. what it achieves.
REST architecture :: REST architecture
-----------------
REST is a *client-server* architecture. The client and the server REST is a *client-server* architecture. The client and the server
both have a different set of concerns. The server stores and/or both have a different set of concerns. The server stores and/or
@ -56,8 +54,7 @@ to extend client functionality. This is optional however because
the client may not be able to download or run this code, and so the client may not be able to download or run this code, and so
a REST component cannot rely on it being executed. a REST component cannot rely on it being executed.
Resources and resource identifiers :: Resources and resource identifiers
----------------------------------
A resource is an abstract concept. In a REST system, any information A resource is an abstract concept. In a REST system, any information
that can be named may be a resource. This includes documents, images, that can be named may be a resource. This includes documents, images,
@ -82,8 +79,7 @@ resources map to a set of one element, for example "user Joe".
Collection of resources map to a set of 0 to N elements, Collection of resources map to a set of 0 to N elements,
for example "all users". for example "all users".
Resource representations :: Resource representations
------------------------
The representation of a resource is a sequence of bytes associated The representation of a resource is a sequence of bytes associated
with metadata. with metadata.
@ -115,8 +111,7 @@ type. Some media types are intended for direct rendering to the
user, while others are intended for automated processing. The user, while others are intended for automated processing. The
media type is a key component of the REST architecture. media type is a key component of the REST architecture.
Self-descriptive messages :: Self-descriptive messages
-------------------------
Messages must be self-descriptive. That means that the data Messages must be self-descriptive. That means that the data
format of a representation must always come with its media format of a representation must always come with its media
@ -137,8 +132,7 @@ This means that you can create your own media types, like
specifications for it and that both endpoints agree about specifications for it and that both endpoints agree about
it then the constraint is respected. it then the constraint is respected.
Hypermedia as the engine of application state :: Hypermedia as the engine of application state
---------------------------------------------
The last constraint is generally where services that claim The last constraint is generally where services that claim
to be RESTful fail. Interactions with a server must be to be RESTful fail. Interactions with a server must be

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@ -1,5 +1,4 @@
Routing ::: Routing
=======
Cowboy does nothing by default. Cowboy does nothing by default.
@ -15,8 +14,7 @@ and then try to find a matching path.
Routes need to be compiled before they can be used by Cowboy. Routes need to be compiled before they can be used by Cowboy.
Structure :: Structure
---------
The general structure for the routes is defined as follow. The general structure for the routes is defined as follow.
@ -51,8 +49,7 @@ Path2 = {PathMatch, Constraints, Handler, Opts}.
Continue reading to learn more about the match syntax and the optional Continue reading to learn more about the match syntax and the optional
constraints. constraints.
Match syntax :: Match syntax
------------
The match syntax is used to associate host names and paths with their The match syntax is used to associate host names and paths with their
respective handlers. respective handlers.
@ -189,8 +186,7 @@ wildcard path, generally used alongside the `OPTIONS` method.
HostMatch = "*". HostMatch = "*".
``` ```
Constraints :: Constraints
-----------
After the matching has completed, the resulting bindings can be tested After the matching has completed, the resulting bindings can be tested
against a set of constraints. Constraints are only tested when the against a set of constraints. Constraints are only tested when the
@ -216,8 +212,7 @@ The value thus returned can be of any type.
Note that constraint functions SHOULD be pure and MUST NOT crash. Note that constraint functions SHOULD be pure and MUST NOT crash.
Compilation :: Compilation
-----------
The structure defined in this chapter needs to be compiled before it is The structure defined in this chapter needs to be compiled before it is
passed to Cowboy. This allows Cowboy to efficiently lookup the correct passed to Cowboy. This allows Cowboy to efficiently lookup the correct
@ -240,8 +235,7 @@ cowboy:start_http(my_http_listener, 100,
Note that this function will return `{error, badarg}` if the structure Note that this function will return `{error, badarg}` if the structure
given is incorrect. given is incorrect.
Live update :: Live update
-----------
You can use the `cowboy:set_env/3` function for updating the dispatch You can use the `cowboy:set_env/3` function for updating the dispatch
list used by routing. This will apply to all new connections accepted list used by routing. This will apply to all new connections accepted

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Static handler ::: Static handler
==============
The static handler is a built-in REST handler for serving files. The static handler is a built-in REST handler for serving files.
It is available as a convenience and provides a quick solution It is available as a convenience and provides a quick solution
@ -20,8 +19,7 @@ client-side caching.
To use the static file handler, simply add routes for it To use the static file handler, simply add routes for it
with the appropriate options. with the appropriate options.
Serve one file :: Serve one file
--------------
You can use the static handler to serve one specific file You can use the static handler to serve one specific file
from an application's private directory. This is particularly from an application's private directory. This is particularly
@ -44,8 +42,7 @@ path to the file relative to the current directory.
{"/", cowboy_static, {file, "/var/www/index.html"}} {"/", cowboy_static, {file, "/var/www/index.html"}}
``` ```
Serve all files from a directory :: Serve all files from a directory
--------------------------------
You can also use the static handler to serve all files that You can also use the static handler to serve all files that
can be found in the configured directory. The handler will can be found in the configured directory. The handler will
@ -72,8 +69,7 @@ set it relative to the current directory.
{"/assets/[...]", cowboy_static, {dir, "/var/www/assets"}} {"/assets/[...]", cowboy_static, {dir, "/var/www/assets"}}
``` ```
Customize the mimetype detection :: Customize the mimetype detection
--------------------------------
By default, Cowboy will attempt to recognize the mimetype By default, Cowboy will attempt to recognize the mimetype
of your static files by looking at the extension. of your static files by looking at the extension.
@ -141,8 +137,7 @@ and `priv_file` options as it avoids needless computation.
[{mimetypes, {<<"text">>, <<"html">>, []}}]}} [{mimetypes, {<<"text">>, <<"html">>, []}}]}}
``` ```
Generate an etag :: Generate an etag
----------------
By default, the static handler will generate an etag header By default, the static handler will generate an etag header
value based on the size and modified time. This solution value based on the size and modified time. This solution

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Protocol upgrades ::: Protocol upgrades
=================
Cowboy features many different handlers, each for different purposes. Cowboy features many different handlers, each for different purposes.
All handlers have a common entry point: the `init/3` function. All handlers have a common entry point: the `init/3` function.

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Handling Websocket connections ::: Handling Websocket connections
==============================
A special handler is required for handling Websocket connections. A special handler is required for handling Websocket connections.
Websocket handlers allow you to initialize the connection, Websocket handlers allow you to initialize the connection,
@ -10,8 +9,7 @@ Websocket handlers essentially act as a bridge between the client
and the Erlang system. They will typically do little more than and the Erlang system. They will typically do little more than
socket communication and decoding/encoding of frames. socket communication and decoding/encoding of frames.
Initialization :: Initialization
--------------
First, the `init/3` callback is called. This callback is common First, the `init/3` callback is called. This callback is common
to all handlers. To establish a Websocket connection, this function to all handlers. To establish a Websocket connection, this function
@ -105,8 +103,7 @@ websocket_info(post_init, Req, State) ->
{ok, Req, State}. {ok, Req, State}.
``` ```
Handling frames from the client :: Handling frames from the client
-------------------------------
Cowboy will call `websocket_handle/3` whenever a text, binary, Cowboy will call `websocket_handle/3` whenever a text, binary,
ping or pong frame arrives from the client. Note that in the ping or pong frame arrives from the client. Note that in the
@ -126,8 +123,7 @@ websocket_handle(_Frame, Req, State) ->
{ok, Req, State}. {ok, Req, State}.
``` ```
Handling Erlang messages :: Handling Erlang messages
------------------------
Cowboy will call `websocket_info/3` whenever an Erlang message Cowboy will call `websocket_info/3` whenever an Erlang message
arrives. arrives.
@ -145,8 +141,7 @@ websocket_info(_Info, Req, State) ->
{ok, Req, State}. {ok, Req, State}.
``` ```
Sending frames to the socket :: Sending frames to the socket
----------------------------
Cowboy allows sending either a single frame or a list of Cowboy allows sending either a single frame or a list of
frames to the socket. Any frame can be sent: text, binary, ping, frames to the socket. Any frame can be sent: text, binary, ping,
@ -176,8 +171,7 @@ be received will not be processed. Also note that when replying
a list of frames that includes close, any frame found after the a list of frames that includes close, any frame found after the
close frame will not be sent. close frame will not be sent.
Ping and timeout :: Ping and timeout
----------------
The biggest performance improvement you can do when dealing The biggest performance improvement you can do when dealing
with a huge number of Websocket connections is to reduce the with a huge number of Websocket connections is to reduce the
@ -208,8 +202,7 @@ websocket_init(_Type, Req, _Opts) ->
This value cannot be changed once it is set. It defaults to This value cannot be changed once it is set. It defaults to
`infinity`. `infinity`.
Hibernate :: Hibernate
---------
Most tuples returned from handler callbacks can include an Most tuples returned from handler callbacks can include an
extra value `hibernate`. After doing any necessary operations extra value `hibernate`. After doing any necessary operations
@ -221,10 +214,9 @@ handle much traffic. It is a good idea to hibernate all
connections by default and investigate only when you start connections by default and investigate only when you start
noticing increased CPU usage. noticing increased CPU usage.
Supporting older browsers :: Supporting older browsers
-------------------------
Unfortunately Websocket is a relatively recent technology, Unfortunately Websocket is a relatively recent technology,
which means that not all browsers support it. A library like which means that not all browsers support it. A library like
[Bullet](https://github.com/extend/bullet) can be used to ^"Bullet^https://github.com/extend/bullet^ can be used to
emulate Websocket connections on older browsers. emulate Websocket connections on older browsers.

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@ -1,11 +1,9 @@
The Websocket protocol ::: The Websocket protocol
======================
This chapter explains what Websocket is and why it is This chapter explains what Websocket is and why it is
a vital component of soft realtime Web applications. a vital component of soft realtime Web applications.
Description :: Description
-----------
Websocket is an extension to HTTP that emulates plain TCP Websocket is an extension to HTTP that emulates plain TCP
connections between the client, typically a Web browser, connections between the client, typically a Web browser,
@ -24,8 +22,7 @@ and all drafts that were previously implemented by browsers,
excluding the initial flawed draft sometimes known as excluding the initial flawed draft sometimes known as
"version 0". "version 0".
Implementation :: Implementation
--------------
Cowboy implements Websocket as a protocol upgrade. Once the Cowboy implements Websocket as a protocol upgrade. Once the
upgrade is performed from the `init/3` callback, Cowboy upgrade is performed from the `init/3` callback, Cowboy

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@ -0,0 +1,101 @@
::: cowboy
The `cowboy` module provides convenience functions for
manipulating Ranch listeners.
:: Types
: http_headers() = [{binary(), iodata()}]
HTTP headers as a list of key/values.
: http_status() = non_neg_integer() | binary()
HTTP status.
A binary status can be used to set a custom message.
: http_version() = 'HTTP/1.1' | 'HTTP/1.0'
HTTP version.
: onrequest_fun() = fun((cowboy_req:req()) -> cowboy_req:req())
Fun called immediately after receiving a request.
It can perform any operation on the Req object, including
reading the request body or replying. If a reply is sent,
the processing of the request ends here, before any middleware
is executed.
: onresponse_fun() = fun((http_status(), http_headers(),
iodata(), cowboy_req:req()) -> cowboy_req:req())
Fun called immediately before sending the response.
It can perform any operation on the Req object, including
reading the request body or replying. If a reply is sent, it
overrides the reply initially sent. The callback will not be
called again for the new reply.
:: Exports
: start_http(Ref, NbAcceptors, TransOpts, ProtoOpts) -> {ok, pid()}
Types:
* Ref = ranch:ref()
* NbAcceptors = non_neg_integer()
* TransOpts = ranch_tcp:opts()
* ProtoOpts = cowboy_protocol:opts()
Start listening for HTTP connections. Returns the pid for this
listener's supervisor.
: start_https(Ref, NbAcceptors, TransOpts, ProtoOpts) -> {ok, pid()}
Types:
* Ref = ranch:ref()
* NbAcceptors = non_neg_integer()
* TransOpts = ranch_ssl:opts()
* ProtoOpts = cowboy_protocol:opts()
Start listening for HTTPS connections. Returns the pid for this
listener's supervisor.
: start_spdy(Ref, NbAcceptors, TransOpts, ProtoOpts) -> {ok, pid()}
Types:
* Ref = ranch:ref()
* NbAcceptors = non_neg_integer()
* TransOpts = ranch_ssl:opts()
* ProtoOpts = cowboy_spdy:opts()
Start listening for SPDY connections. Returns the pid for this
listener's supervisor.
: stop_listener(Ref) -> ok | {error, not_found}
Types:
* Ref = ranch:ref()
Stop a previously started listener.
: set_env(Ref, Name, Value) -> ok
Types:
* Ref = ranch:ref()
* Name = atom()
* Value = any()
Set or update an environment value for an already running listener.
This will take effect on all subsequent connections.
:: See also
The ^"Ranch guide^http://ninenines.eu/docs/en/ranch/HEAD/guide
provides detailed information about how listeners work.

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@ -1,10 +1,8 @@
The Cowboy Application ::: The Cowboy Application
======================
Small, fast, modular HTTP server. Small, fast, modular HTTP server.
Dependencies :: Dependencies
------------
The `cowboy` application uses the Erlang applications `ranch` The `cowboy` application uses the Erlang applications `ranch`
for listening and accepting TCP connections, `crypto` for for listening and accepting TCP connections, `crypto` for
@ -19,8 +17,7 @@ The `cowboy` application also uses the Erlang applications
`asn1`, `public_key` and `ssl` when listening for HTTPS connections. `asn1`, `public_key` and `ssl` when listening for HTTPS connections.
These are started automatically if they weren't before. These are started automatically if they weren't before.
Environment :: Environment
-----------
The `cowboy` application does not define any application The `cowboy` application does not define any application
environment configuration parameters. environment configuration parameters.

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@ -1,25 +1,24 @@
cowboy_handler ::: cowboy_handler
==============
The `cowboy_handler` middleware executes the handler passed The `cowboy_handler` middleware executes the handler passed
through the environment values `handler` and `handler_opts`, through the environment values `handler` and `handler_opts`,
and add the result of this execution to the environment as and adds the result of this execution to the environment as
the value `result`, indicating that the request has been the value `result`, indicating that the request has been
handled and received a response. handled and received a response.
Environment input: Environment input:
* handler = module() * handler = module()
* handler_opts = any() * handler_opts = any()
Environment output: Environment output:
* result = ok * result = ok
Types :: Types
-----
None. None.
Exports :: Exports
-------
None. None.

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@ -0,0 +1,57 @@
::: cowboy_http_handler
The `cowboy_http_handler` behaviour defines the interface used
by plain HTTP handlers.
Unless noted otherwise, the callbacks will be executed sequentially.
:: Types
None.
:: Callbacks
: init({TransportName, ProtocolName}, Req, Opts)
-> {ok, Req, State} | {shutdown, Req, State}
Types:
* TransportName = tcp | ssl | atom()
* ProtocolName = http | atom()
* Req = cowboy_req:req()
* Opts = any()
* State = any()
Initialize the state for this request.
The `shutdown` return value can be used to skip the `handle/2`
call entirely.
: handle(Req, State) -> {ok, Req, State}
Types:
* Req = cowboy_req:req()
* State = any()
Handle the request.
This callback is where the request is handled and a response
should be sent. If a response is not sent, Cowboy will send
a `204 No Content` response automatically.
: terminate(Reason, Req, State) -> ok
Types:
* Reason = {normal, shutdown} | {error, atom()}
* Req = cowboy_req:req()
* State = any()
Perform any necessary cleanup of the state.
This callback should release any resource currently in use,
clear any active timer and reset the process to its original
state, as it might be reused for future requests sent on the
same connection. Typical plain HTTP handlers rarely need to
use it.

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@ -0,0 +1,91 @@
::: cowboy_loop_handler
The `cowboy_loop_handler` behaviour defines the interface used
by HTTP handlers that do not send a response directly, instead
requiring a receive loop to process Erlang messages.
This interface is best fit for long-polling types of requests.
The `init/3` callback will always be called, followed by zero
or more calls to `info/3`. The `terminate/3` callback will
always be called last.
:: Types
None.
:: Callbacks
: init({TransportName, ProtocolName}, Req, Opts)
-> {loop, Req, State}
| {loop, Req, State, hibernate}
| {loop, Req, State, Timeout}
| {loop, Req, State, Timeout, hibernate}
| {shutdown, Req, State}
Types:
* TransportName = tcp | ssl | atom()
* ProtocolName = http | atom()
* Req = cowboy_req:req()
* Opts = any()
* State = any()
* Timeout = timeout()
Initialize the state for this request.
This callback will typically be used to register this process
to an event manager or a message queue in order to receive
the messages the handler wants to process.
The receive loop will run for a duration of up to `Timeout`
milliseconds after it last received data from the socket,
at which point it will stop and send a `204 No Content` reply.
By default this value is set to `infinity`. It is recommended
to either set this value or ensure by any other mechanism
that the handler will be closed after a certain period of
inactivity.
The `hibernate` option will hibernate the process until it
starts receiving messages.
The `shutdown` return value can be used to skip the receive
loop entirely.
: info(Info, Req, State) -> {ok, Req, State} | {loop, Req, State}
| {loop, Req, State, hibernate}
Types:
* Info = any()
* Req = cowboy_req:req()
* State = any()
Handle the Erlang message received.
This function will be called every time an Erlang message
has been received. The message can be any Erlang term.
The `ok` return value can be used to stop the receive loop,
typically because a response has been sent.
The `hibernate` option will hibernate the process until
it receives another message.
: terminate(Reason, Req, State) -> ok
Types:
* Reason = {normal, shutdown} | {normal, timeout} | {error, closed} | {error, overflow} | {error, atom()}
* Req = cowboy_req:req()
* State = any()
Perform any necessary cleanup of the state.
This callback will typically unregister from any event manager
or message queue it registered to in `init/3`.
This callback should release any resource currently in use,
clear any active timer and reset the process to its original
state, as it might be reused for future requests sent on the
same connection.

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@ -0,0 +1,54 @@
::: cowboy_middleware
The `cowboy_middleware` behaviour defines the interface used
by Cowboy middleware modules.
Middlewares process the request sequentially in the order they
are configured.
:: Types
: env() = [{atom(), any()}]
The environment variable.
One is created for every request. It is passed to each
middleware module executed and subsequently returned,
optionally with its contents modified.
:: Callbacks
: execute(Req, Env)
-> {ok, Req, Env}
| {suspend, Module, Function, Args}
| {halt, Req}
| {error, StatusCode, Req}
Types:
* Req = cowboy_req:req()
* Env = env()
* Module = module()
* Function = atom()
* Args = [any()]
* StatusCode = cowboy:http_status()
Execute the middleware.
The `ok` return value indicates that everything went well
and that Cowboy should continue processing the request. A
response may or may not have been sent.
The `suspend` return value will hibernate the process until
an Erlang message is received. Note that when resuming, any
previous stacktrace information will be gone.
The `halt` return value stops Cowboy from doing any further
processing of the request, even if there are middlewares
that haven't been executed yet. The connection may be left
open to receive more requests from the client.
The `error` return value sends an error response identified
by the `StatusCode` and then proceeds to terminate the
connection. Middlewares that haven't been executed yet
will not be called.

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::: cowboy_protocol
The `cowboy_protocol` module implements HTTP/1.1 and HTTP/1.0
as a Ranch protocol.
:: Types
: opts() = [{compress, boolean()}
| {env, cowboy_middleware:env()}
| {max_empty_lines, non_neg_integer()}
| {max_header_name_length, non_neg_integer()}
| {max_header_value_length, non_neg_integer()}
| {max_headers, non_neg_integer()}
| {max_keepalive, non_neg_integer()}
| {max_request_line_length, non_neg_integer()}
| {middlewares, [module()]}
| {onrequest, cowboy:onrequest_fun()}
| {onresponse, cowboy:onresponse_fun()}
| {timeout, timeout()}]
Configuration for the HTTP protocol handler.
This configuration is passed to Cowboy when starting listeners
using `cowboy:start_http/4` or `cowboy:start_https/4` functions.
It can be updated without restarting listeners using the
Ranch functions `ranch:get_protocol_options/1` and
`ranch:set_protocol_options/2`.
:: Option descriptions
The default value is given next to the option name.
: compress (false)
When enabled, Cowboy will attempt to compress the response body.
: env ([{listener, Ref}])
Initial middleware environment.
: max_empty_lines (5)
Maximum number of empty lines before a request.
: max_header_name_length (64)
Maximum length of header names.
: max_header_value_length (4096)
Maximum length of header values.
: max_headers (100)
Maximum number of headers allowed per request.
: max_keepalive (100)
Maximum number of requests allowed per connection.
: max_request_line_length (4096)
Maximum length of the request line.
: middlewares ([cowboy_router, cowboy_handler])
List of middlewares to execute for every requests.
: onrequest (undefined)
Fun called every time a request is received.
: onresponse (undefined)
Fun called every time a response is sent.
: timeout (5000)
Time in ms with no requests before Cowboy closes the connection.
:: Exports
None.

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::: cowboy_req
The `cowboy_req` module provides functions to access, manipulate
and respond to requests.
The functions in this module follow patterns for their return types,
based on the kind of function.
* access: `{Value, Req}`
* action: `{Result, Req} | {Result, Value, Req} | {error, atom()}`
* modification: `Req`
* question: `boolean()`
The only exception is the `chunk/2` function which may return `ok`.
Whenever `Req` is returned, you must use this returned value and
ignore any previous you may have had. This value contains various
state informations which are necessary for Cowboy to do some lazy
evaluation or cache results where appropriate.
All functions which perform an action should only be called once.
This includes reading the request body or replying. Cowboy will
generally throw an error on the second call.
It is highly discouraged to pass the Req object to another process.
Doing so and calling `cowboy_req` functions from it leads to
undefined behavior.
:: Types
: body_opts() = [{continue, boolean()}
| {length, non_neg_integer()}
| {read_length, non_neg_integer()}
| {read_timeout, timeout()}
| {transfer_decode, transfer_decode_fun(), any()}
| {content_decode, content_decode_fun()}]
Request body reading options.
: cookie_opts() = [{max_age, non_neg_integer()}
| {domain, binary()} | {path, binary()}
| {secure, boolean()} | {http_only, boolean()}]
Cookie options.
: req() - opaque to the user
The Req object.
All functions in this module receive a `Req` as argument,
and most of them return a new object labelled `Req2` in
the function descriptions below.
:: Request related exports
: binding(Name, Req) -> binding(Name, Req, undefined)
: binding(Name, Req, Default) -> {Value, Req2}
Types:
* Name = atom()
* Default = any()
* Value = any() | Default
Return the value for the given binding.
By default the value is a binary, however constraints may change
the type of this value (for example automatically converting
numbers to integer).
: bindings(Req) -> {[{Name, Value}], Req2}
Types:
* Name = atom()
* Value = any()
Return all bindings.
By default the value is a binary, however constraints may change
the type of this value (for example automatically converting
numbers to integer).
: cookie(Name, Req) -> cookie(Name, Req, undefined)
: cookie(Name, Req, Default) -> {Value, Req2}
Types:
* Name = binary()
* Default = any()
* Value = binary() | Default
Return the value for the given cookie.
Cookie names are case sensitive.
: cookies(Req) -> {[{Name, Value}], Req2}
Types:
* Name = binary()
* Value = binary()
Return all cookies.
: header(Name, Req) -> header(Name, Req, undefined)
: header(Name, Req, Default) -> {Value, Req2}
Types:
* Name = binary()
* Default = any()
* Value = binary() | Default
Return the value for the given header.
While header names are case insensitive, this function expects
the name to be a lowercase binary.
: headers(Req) -> {Headers, Req2}
Types:
* Headers = cowboy:http_headers()
Return all headers.
: host(Req) -> {Host, Req2}
Types:
* Host = binary()
Return the requested host.
: host_info(Req) -> {HostInfo, Req2}
Types:
* HostInfo = cowboy_router:tokens() | undefined
Return the extra tokens from matching against `...` during routing.
: host_url(Req) -> {HostURL, Req2}
Types:
* HostURL = binary() | undefined
Return the requested URL excluding the path component.
This function will always return `undefined` until the
`cowboy_router` middleware has been executed. This includes
the `onrequest` hook.
: meta(Name, Req) -> meta(Name, Req, undefined)
: meta(Name, Req, Default) -> {Value, Req2}
Types:
* Name = atom()
* Default = any()
* Value = any()
Return metadata about the request.
: method(Req) -> {Method, Req2}
Types:
* Method = binary()
Return the method.
Methods are case sensitive. Standard methods are always uppercase.
: parse_header(Name, Req) ->
: parse_header(Name, Req, Default) -> {ok, ParsedValue, Req2}
| {undefined, Value, Req2} | {error, badarg}
Types:
* Name = binary()
* Default = any()
* ParsedValue - see below
* Value = any()
Parse the given header.
While header names are case insensitive, this function expects
the name to be a lowercase binary.
The `parse_header/2` function will call `parser_header/3` with a
different default value depending on the header being parsed. The
following table summarizes the default values used.
|| Header name Default value
|
| transfer-encoding `[<<"identity">>]`
| Any other header `undefined`
The parsed value differs depending on the header being parsed. The
following table summarizes the different types returned.
|| Header name Type
|
| accept `[{{Type, SubType, Params}, Quality, AcceptExt}]`
| accept-charset `[{Charset, Quality}]`
| accept-encoding `[{Encoding, Quality}]`
| accept-language `[{LanguageTag, Quality}]`
| authorization `{AuthType, Credentials}`
| content-length `non_neg_integer()`
| content-type `{Type, SubType, ContentTypeParams}`
| cookie `[{binary(), binary()}]`
| expect `[Expect | {Expect, ExpectValue, Params}]`
| if-match `'*' | [{weak | strong, OpaqueTag}]`
| if-modified-since `calendar:datetime()`
| if-none-match `'*' | [{weak | strong, OpaqueTag}]`
| if-unmodified-since `calendar:datetime()`
| range `{Unit, [Range]}`
| sec-websocket-protocol `[binary()]`
| transfer-encoding `[binary()]`
| upgrade `[binary()]`
| x-forwarded-for `[binary()]`
Types for the above table:
* Type = SubType = Charset = Encoding = LanguageTag = binary()
* AuthType = Expect = OpaqueTag = Unit = binary()
* Params = ContentTypeParams = [{binary(), binary()}]
* Quality = 0..1000
* AcceptExt = [{binary(), binary()} | binary()]
* Credentials - see below
* Range = {non_neg_integer(), non_neg_integer() | infinity} | neg_integer()
The cookie names and values, the values of the sec-websocket-protocol
and x-forwarded-for headers, the values in `AcceptExt` and `Params`,
the authorization `Credentials`, the `ExpectValue` and `OpaqueTag`
are case sensitive. All values in `ContentTypeParams` are case sensitive
except the value of the charset parameter, which is case insensitive.
All other values are case insensitive and will be returned as lowercase.
The headers accept, accept-encoding and cookie headers can return
an empty list. Others will return `{error, badarg}` if the header
value is empty.
The authorization header parsing code currently only supports basic
HTTP authentication. The `Credentials` type is thus `{Username, Password}`
with `Username` and `Password` being `binary()`.
The range header value `Range` can take three forms:
* `{From, To}`: from `From` to `To` units
* `{From, infinity}`: everything after `From` units
* `-Final`: the final `Final` units
An `undefined` tuple will be returned if Cowboy doesn't know how
to parse the requested header.
: path(Req) -> {Path, Req2}
Types:
* Path = binary()
Return the requested path.
: path_info(Req) -> {PathInfo, Req2}
Types:
* PathInfo = cowboy_router:tokens() | undefined
Return the extra tokens from matching against `...` during routing.
: peer(Req) -> {Peer, Req2}
Types:
* Peer = {inet:ip_address(), inet:port_number()}
Return the client's IP address and port number.
: port(Req) -> {Port, Req2}
Types:
* Port = inet:port_number()
Return the request's port.
The port returned by this function is obtained by parsing
the host header. It may be different than the actual port
the client used to connect to the Cowboy server.
: qs(Req) -> {QueryString, Req2}
Types:
* QueryString = binary()
Return the request's query string.
: qs_val(Name, Req) -> qs_val(Name, Req, undefined)
: qs_val(Name, Req, Default) -> {Value, Req2}
Types:
* Name = binary()
* Default = any()
* Value = binary() | true
Return a value from the request's query string.
The value `true` will be returned when the name was found
in the query string without an associated value.
: qs_vals(Req) -> {[{Name, Value}], Req2}
Types:
* Name = binary()
* Value = binary() | true
Return the request's query string as a list of tuples.
The value `true` will be returned when a name was found
in the query string without an associated value.
: set_meta(Name, Value, Req) -> Req2
Types:
* Name = atom()
* Value = any()
Set metadata about the request.
An existing value will be overwritten.
: url(Req) -> {URL, Req2}
Types:
* URL = binary() | undefined
Return the requested URL.
This function will always return `undefined` until the
`cowboy_router` middleware has been executed. This includes
the `onrequest` hook.
: version(Req) -> {Version, Req2}
Types:
* Version = cowboy:http_version()
Return the HTTP version used for this request.
:: Request body related exports
: body(Req) -> body(Req, [])
: body(Req, Opts) -> {ok, Data, Req2} | {more, Data, Req2} | {error, Reason}
Types:
* Opts = [body_opt()]
* Data = binary()
* Reason = atom()
Read the request body.
This function will read a chunk of the request body. If there is
more data to be read after this function call, then a `more` tuple
is returned. Otherwise an `ok` tuple is returned.
Cowboy will automatically send a `100 Continue` reply if
required. If this behavior is not desirable, it can be disabled
by setting the `continue` option to `false`.
Cowboy will by default attempt to read up to 8MB of the body,
but in chunks of 1MB. It will use a timeout of 15s per chunk.
All these values can be changed using the `length`, `read_length`
and `read_timeout` options respectively. Note that the size
of the data may not be the same as requested as the decoding
functions may grow or shrink it, and Cowboy makes not attempt
at returning an exact amount.
Cowboy will properly handle chunked transfer-encoding by
default. If any other transfer-encoding or content-encoding
has been used for the request, custom decoding functions
can be used. The `content_decode` and `transfer_decode`
options allow setting the decode functions manually.
After the body has been streamed fully, Cowboy will remove
the transfer-encoding header from the Req object, and add
the content-length header if it wasn't already there.
This function can only be called once. Cowboy will not cache
the result of this call.
: body_length(Req) -> {Length, Req2}
Types:
* Length = non_neg_integer() | undefined
Return the length of the request body.
The length will only be returned if the request does not
use any transfer-encoding and if the content-length header
is present.
: body_qs(Req) -> body_qs(Req,
[{length, 64000}, {read_length, 64000}, {read_timeout, 5000}])
: body_qs(Req, Opts) -> {ok, [{Name, Value}], Req2}
| {badlength, Req2} | {error, Reason}
Types:
* Opts = [body_opt()]
* Name = binary()
* Value = binary() | true
* Reason = chunked | badlength | atom()
Return the request body as a list of tuples.
This function will parse the body assuming the content-type
application/x-www-form-urlencoded, commonly used for the
query string.
This function calls `body/2` for reading the body, with the
same options it received. By default it will attempt to read
a body of 64KB in one chunk, with a timeout of 5s. If the
body is larger then a `badlength` tuple is returned.
This function can only be called once. Cowboy will not cache
the result of this call.
: has_body(Req) -> boolean()
Return whether the request has a body.
: part(Req) -> part(Req,
[{length, 64000}, {read_length, 64000}, {read_timeout, 5000}])
: part(Req, Opts) -> {ok, Headers, Req2} | {done, Req2}
Types:
* Opts = [body_opt()]
* Headers = cow_multipart:headers()
Read the headers for the next part of the multipart message.
Cowboy will skip any data remaining until the beginning of
the next part. This includes the preamble to the multipart
message but also the body of a previous part if it hasn't
been read. Both are skipped automatically when calling this
function.
The headers returned are MIME headers, NOT HTTP headers.
They can be parsed using the functions from the `cow_multipart`
module. In addition, the `cow_multipart:form_data/1` function
can be used to quickly figure out `multipart/form-data` messages.
It takes the list of headers and returns whether this part is
a simple form field or a file being uploaded.
Note that once a part has been read, or skipped, it cannot
be read again.
This function calls `body/2` for reading the body, with the
same options it received. By default it will only read chunks
of 64KB with a timeout of 5s. This is tailored for reading
part headers, not for skipping the previous part's body.
You might want to consider skipping large parts manually.
: part_body(Req) -> part_body(Req, [])
: part_body(Req, Opts) -> {ok, Data, Req2} | {more, Data, Req2}
Types:
* Opts = [body_opt()]
* Data = binary()
Read the body of the current part of the multipart message.
This function calls `body/2` for reading the body, with the
same options it received. It uses the same defaults.
If there are more data to be read from the socket for this
part, the function will return what it could read inside a
`more` tuple. Otherwise, it will return an `ok` tuple.
Calling this function again after receiving a `more` tuple
will return another chunk of body. The last chunk will be
returned inside an `ok` tuple.
Note that once the body has been read, fully or partially,
it cannot be read again.
:: Response related exports
: chunk(Data, Req) -> ok | {error, Reason}
Types:
* Data = iodata()
* Reason = atom()
Send a chunk of data.
This function should be called as many times as needed
to send data chunks after calling `chunked_reply/{2,3}`.
When the method is HEAD, no data will actually be sent.
If the request uses HTTP/1.0, the data is sent directly
without wrapping it in an HTTP/1.1 chunk, providing
compatibility with older clients.
: chunked_reply(StatusCode, Req) -> chunked_reply(StatusCode, [], Req)
: chunked_reply(StatusCode, Headers, Req) -> {ok, Req2}
Types:
* StatusCode = cowboy:http_status()
* Headers = cowboy:http_headers()
Send a response using chunked transfer-encoding.
This function effectively sends the response status line
and headers to the client.
This function will not send any body set previously. After
this call the handler must use the `chunk/2` function
repeatedly to send the body in as many chunks as needed.
If the request uses HTTP/1.0, the data is sent directly
without wrapping it in an HTTP/1.1 chunk, providing
compatibility with older clients.
This function can only be called once, with the exception
of overriding the response in the `onresponse` hook.
: continue(Req) -> ok | {error, Reason}
Types:
* Reason = atom()
Send a 100 Continue intermediate reply.
This reply is required before the client starts sending the
body when the request contains the `expect` header with the
`100-continue` value.
Cowboy will send this automatically when required. However
you may want to do it manually by disabling this behavior
with the `continue` body option and then calling this
function.
: delete_resp_header(Name, Req) -> Req2
Types:
* Name = binary()
Delete the given response header.
While header names are case insensitive, this function expects
the name to be a lowercase binary.
: has_resp_body(Req) -> boolean()
Return whether a response body has been set.
This function will return false if a response body has
been set with a length of 0.
: has_resp_header(Name, Req) -> boolean()
Types:
* Name = binary()
Return whether the given response header has been set.
While header names are case insensitive, this function expects
the name to be a lowercase binary.
: reply(StatusCode, Req) -> reply(StatusCode, [], Req)
: reply(StatusCode, Headers, Req) - see below
: reply(StatusCode, Headers, Body, Req) -> {ok, Req2}
Types:
* StatusCode = cowboy:http_status()
* Headers = cowboy:http_headers()
* Body = iodata()
Send a response.
This function effectively sends the response status line,
headers and body to the client, in a single send function
call.
The `reply/2` and `reply/3` functions will send the body
set previously, if any. The `reply/4` function overrides
any body set previously and sends `Body` instead.
If a body function was set, and `reply/2` or `reply/3` was
used, it will be called before returning.
No more data can be sent to the client after this function
returns.
This function can only be called once, with the exception
of overriding the response in the `onresponse` hook.
: set_resp_body(Body, Req) -> Req2
Types:
* Body = iodata()
Set a response body.
This body will not be sent if `chunked_reply/{2,3}` or
`reply/4` is used, as they override it.
: set_resp_body_fun(Fun, Req) -> Req2
: set_resp_body_fun(Length, Fun, Req) -> Req2
Types:
* Fun = fun((Socket, Transport) -> ok)
* Socket = inet:socket()
* Transport = module()
* Length = non_neg_integer()
Set a fun for sending the response body.
If a `Length` is provided, it will be sent in the
content-length header in the response. It is recommended
to set the length if it can be known in advance. Otherwise,
the transfer-encoding header will be set to identity.
This function will only be called if the response is sent
using the `reply/2` or `reply/3` function.
The fun will receive the Ranch `Socket` and `Transport` as
arguments. Only send and sendfile operations are supported.
: set_resp_body_fun(chunked, Fun, Req) -> Req2
Types:
* Fun = fun((ChunkFun) -> ok)
* ChunkFun = fun((iodata()) -> ok | {error, atom()})
Set a fun for sending the response body using chunked transfer-encoding.
This function will only be called if the response is sent
using the `reply/2` or `reply/3` function.
The fun will receive another fun as argument. This fun is to
be used to send chunks in a similar way to the `chunk/2` function,
except the fun only takes one argument, the data to be sent in
the chunk.
: set_resp_cookie(Name, Value, Opts, Req) -> Req2
Types:
* Name = iodata()
* Value = iodata()
* Opts = cookie_opts()
Set a cookie in the response.
Cookie names are case sensitive.
: set_resp_header(Name, Value, Req) -> Req2
Types:
* Name = binary()
* Value = iodata()
Set a response header.
You should use `set_resp_cookie/4` instead of this function
to set cookies.
:: Misc. exports
: compact(Req) -> Req2
Remove any non-essential data from the Req object.
Long-lived connections usually only need to manipulate the
Req object at initialization. Compacting allows saving up
memory by discarding extraneous information.

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::: cowboy_rest
The `cowboy_rest` module implements REST semantics on top of
the HTTP protocol.
This module cannot be described as a behaviour due to most of
the callbacks it defines being optional. It has the same
semantics as a behaviour otherwise.
The only mandatory callback is `init/3`, needed to perform
the protocol upgrade.
:: Types
None.
:: Meta values
: charset
Type: binary()
Negotiated charset.
This value may not be defined if no charset was negotiated.
: language
Type: binary()
Negotiated language.
This value may not be defined if no language was negotiated.
: media_type
Type: {binary(), binary(), '*' | [{binary(), binary()}]}
Negotiated media-type.
The media-type is the content-type, excluding the charset.
This value is always defined after the call to
`content_types_provided/2`.
:: Callbacks
: init({TransportName, ProtocolName}, Req, Opts)
-> {upgrade, protocol, cowboy_rest}
| {upgrade, protocol, cowboy_rest, Req, Opts}
Types:
* TransportName = tcp | ssl | atom()
* ProtocolName = http | atom()
* Req = cowboy_req:req()
* Opts = any()
Upgrade the protocol to `cowboy_rest`.
This is the only mandatory callback.
: rest_init(Req, Opts) -> {ok, Req, State}
Types:
* Req = cowboy_req:req()
* Opts = any()
* State = any()
Initialize the state for this request.
: rest_terminate(Req, State) -> ok
Types:
* Req = cowboy_req:req()
* State = any()
Perform any necessary cleanup of the state.
This callback should release any resource currently in use,
clear any active timer and reset the process to its original
state, as it might be reused for future requests sent on the
same connection.
: Callback(Req, State) -> {Value, Req, State} | {halt, Req, State}
Types:
* Callback - one of the REST callbacks described below
* Req = cowboy_req:req()
* State = any()
* Value - see the REST callbacks description below
Please see the REST callbacks description below for details
on the `Value` type, the default value if the callback is
not defined, and more general information on when the
callback is called and what its intended use is.
The `halt` tuple can be returned to stop REST processing.
It is up to the resource code to send a reply before that,
otherwise a `204 No Content` will be sent.
:: REST callbacks description
: allowed_methods
* Methods: all
* Value type: [binary()]
* Default value: [<<"GET">>, <<"HEAD">>, <<"OPTIONS">>]
Return the list of allowed methods.
Methods are case sensitive. Standard methods are always uppercase.
: allow_missing_post
* Methods: POST
* Value type: boolean()
* Default value: true
Return whether POST is allowed when the resource doesn't exist.
Returning `true` here means that a new resource will be
created. The URL to the created resource should also be
returned from the `AcceptResource` callback.
: charsets_provided
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Value type: [binary()]
* Skip to the next step if undefined
Return the list of charsets the resource provides.
The list must be ordered in order of preference.
If the accept-charset header was not sent, the first charset
in the list will be selected. Otherwise Cowboy will select
the most appropriate charset from the list.
The chosen charset will be set in the `Req` object as the meta
value `charset`.
While charsets are case insensitive, this callback is expected
to return them as lowercase binary.
: content_types_accepted
* Methods: POST, PUT, PATCH
* No default
Types:
* Value = [{binary() | {Type, SubType, Params}, AcceptResource}]
* Type = SubType = binary()
* Params = '*' | [{binary(), binary()}]
* AcceptResource = atom()
Return the list of content-types the resource accepts.
The list must be ordered in order of preference.
Each content-type can be given either as a binary string or as
a tuple containing the type, subtype and parameters.
Cowboy will select the most appropriate content-type from the list.
If any parameter is acceptable, then the tuple form should be used
with parameters set to `'*'`. If the parameters value is set to `[]`
only content-type values with no parameters will be accepted. All
parameter values are treated in a case sensitive manner except the
`charset` parameter, if present, which is case insensitive.
This function will be called for POST, PUT and PATCH requests.
It is entirely possible to define different callbacks for different
methods if the handling of the request differs. Simply verify
what the method is with `cowboy_req:method/1` and return a
different list for each methods.
The `AcceptResource` value is the name of the callback that will
be called if the content-type matches. It is defined as follow.
* Value type: true | {true, URL} | false
* No default
Process the request body.
This function should create or update the resource with the
information contained in the request body. This information
may be full or partial depending on the request method.
If the request body was processed successfully, `true` or
`{true, URL}` may be returned. If an URL is provided, the
response will redirect the client to the location of the
resource.
If a response body must be sent, the appropriate media-type, charset
and language can be retrieved using the `cowboy_req:meta/{2,3}`
functions. The respective keys are `media_type`, `charset`
and `language`. The body can be set using `cowboy_req:set_resp_body/2`.
: content_types_provided
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Default value: [{{<<"text">>, <<"html">>, '*'}, to_html}]
Types:
* Value = [{binary() | {Type, SubType, Params}, ProvideResource}]
* Type = SubType = binary()
* Params = '*' | [{binary(), binary()}]
* ProvideResource = atom()
Return the list of content-types the resource provides.
The list must be ordered in order of preference.
Each content-type can be given either as a binary string or as
a tuple containing the type, subtype and parameters.
Cowboy will select the most appropriate content-type from the list.
If any parameter is acceptable, then the tuple form should be used
with parameters set to `'*'`. If the parameters value is set to `[]`
only content-type values with no parameters will be accepted. All
parameter values are treated in a case sensitive manner except the
`charset` parameter, if present, which is case insensitive.
The `ProvideResource` value is the name of the callback that will
be called if the content-type matches. It will only be called when
a representation of the resource needs to be returned. It is defined
as follow.
* Methods: GET, HEAD
* Value type: iodata() | {stream, Fun} | {stream, Len, Fun} | {chunked, ChunkedFun}
* No default
Return the response body.
The response body may be provided directly or through a fun.
If a fun tuple is returned, the appropriate `set_resp_body_fun`
function will be called. Please refer to the documentation for
these functions for more information about the types.
The call to this callback happens a good time after the call to
`content_types_provided/2`, when it is time to start rendering
the response body.
: delete_completed
* Methods: DELETE
* Value type: boolean()
* Default value: true
Return whether the delete action has been completed.
This function should return `false` if there is no guarantee
that the resource gets deleted immediately from the system,
including from any internal cache.
When this function returns `false`, a `202 Accepted`
response will be sent instead of a `200 OK` or `204 No Content`.
: delete_resource
* Methods: DELETE
* Value type: boolean()
* Default value: false
Delete the resource.
The value returned indicates if the action was successful,
regardless of whether the resource is immediately deleted
from the system.
: expires
* Methods: GET, HEAD
* Value type: calendar:datetime() | binary() | undefined
* Default value: undefined
Return the date of expiration of the resource.
This date will be sent as the value of the expires header.
: forbidden
* Methods: all
* Value type: boolean()
* Default value: false
Return whether access to the resource is forbidden.
A `403 Forbidden` response will be sent if this
function returns `true`. This status code means that
access is forbidden regardless of authentication,
and that the request shouldn't be repeated.
: generate_etag
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Value type: binary() | {weak | strong, binary()}
* Default value: undefined
Return the entity tag of the resource.
This value will be sent as the value of the etag header.
If a binary is returned, then the value will be parsed
to the tuple form automatically. The value must be in
the same format as the etag header, including quotes.
: is_authorized
* Methods: all
* Value type: true | {false, AuthHeader}
* Default value: true
Return whether the user is authorized to perform the action.
This function should be used to perform any necessary
authentication of the user before attempting to perform
any action on the resource.
If the authentication fails, the value returned will be sent
as the value for the www-authenticate header in the
`401 Unauthorized` response.
: is_conflict
* Methods: PUT
* Value type: boolean()
* Default value: false
Return whether the put action results in a conflict.
A `409 Conflict` response will be sent if this function
returns `true`.
: known_content_type
* Methods: all
* Value type: boolean()
* Default value: true
Return whether the content-type is known.
This function determines if the server understands the
content-type, regardless of its use by the resource.
: known_methods
* Methods: all
* Value type: [binary()]
* Default value: [<<"GET">>, <<"HEAD">>, <<"POST">>, <<"PUT">>, <<"PATCH">>, <<"DELETE">>, <<"OPTIONS">>]
Return the list of known methods.
The full list of methods known by the server should be
returned, regardless of their use in the resource.
The default value lists the methods Cowboy knows and
implement in `cowboy_rest`.
Methods are case sensitive. Standard methods are always uppercase.
: languages_provided
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Value type: [binary()]
* Skip to the next step if undefined
Return the list of languages the resource provides.
The list must be ordered in order of preference.
If the accept-language header was not sent, the first language
in the list will be selected. Otherwise Cowboy will select
the most appropriate language from the list.
The chosen language will be set in the `Req` object as the meta
value `language`.
While languages are case insensitive, this callback is expected
to return them as lowercase binary.
: last_modified
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Value type: calendar:datetime()
* Default value: undefined
Return the date of last modification of the resource.
This date will be used to test against the if-modified-since
and if-unmodified-since headers, and sent as the last-modified
header in the response of GET and HEAD requests.
: malformed_request
* Methods: all
* Value type: boolean()
* Default value: false
Return whether the request is malformed.
Cowboy has already performed all the necessary checks
by the time this function is called, so few resources
are expected to implement it.
The check is to be done on the request itself, not on
the request body, which is processed later.
: moved_permanently
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Value type: {true, URL} | false
* Default value: false
Return whether the resource was permanently moved.
If it was, its new URL is also returned and sent in the
location header in the response.
: moved_temporarily
* Methods: GET, HEAD, POST, PATCH, DELETE
* Value type: {true, URL} | false
* Default value: false
Return whether the resource was temporarily moved.
If it was, its new URL is also returned and sent in the
location header in the response.
: multiple_choices
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Value type: boolean()
* Default value: false
Return whether there are multiple representations of the resource.
This function should be used to inform the client if there
are different representations of the resource, for example
different content-type. If this function returns `true`,
the response body should include information about these
different representations using `cowboy_req:set_resp_body/2`.
The content-type of the response should be the one previously
negociated and that can be obtained by calling
`cowboy_req:meta(media_type, Req)`.
: options
* Methods: OPTIONS
* Value type: ok
* Default value: ok
Handle a request for information.
The response should inform the client the communication
options available for this resource.
By default, Cowboy will send a `200 OK` response with the
allow header set.
: previously_existed
* Methods: GET, HEAD, POST, PATCH, DELETE
* Value type: boolean()
* Default value: false
Return whether the resource existed previously.
: resource_exists
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Value type: boolean()
* Default value: true
Return whether the resource exists.
If it exists, conditional headers will be tested before
attempting to perform the action. Otherwise, Cowboy will
check if the resource previously existed first.
: service_available
* Methods: all
* Value type: boolean()
* Default value: true
Return whether the service is available.
This function can be used to test that all relevant backend
systems are up and able to handle requests.
A `503 Service Unavailable` response will be sent if this
function returns `false`.
: uri_too_long
* Methods: all
* Value type: boolean()
* Default value: false
Return whether the requested URI is too long.
Cowboy has already performed all the necessary checks
by the time this function is called, so few resources
are expected to implement it.
A `414 Request-URI Too Long` response will be sent if this
function returns `true`.
: valid_content_headers
* Methods: all
* Value type: boolean()
* Default value: true
Return whether the content-* headers are valid.
This also applies to the transfer-encoding header. This
function must return `false` for any unknown content-*
headers, or if the headers can't be understood. The
function `cowboy_req:parse_header/2` can be used to
quickly check the headers can be parsed.
A `501 Not Implemented` response will be sent if this
function returns `false`.
: valid_entity_length
* Methods: all
* Value type: boolean()
* Default value: true
Return whether the request body length is within acceptable boundaries.
A `413 Request Entity Too Large` response will be sent if this
function returns `false`.
: variances
* Methods: GET, HEAD, POST, PUT, PATCH, DELETE
* Value type: [binary()]
* Default value: []
Return the list of headers that affect the representation of the resource.
These request headers return the same resource but with different
parameters, like another language or a different content-type.
Cowboy will automatically add the accept, accept-language and
accept-charset headers to the list if the respective functions
were defined in the resource.
This operation is performed right before the `resource_exists/2`
callback. All responses past that point will contain the vary
header which holds this list.

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::: cowboy_router
The `cowboy_router` middleware maps the requested host and
path to the handler to be used for processing the request.
It uses the dispatch rules compiled from the routes given
to the `compile/1` function for this purpose. It adds the
handler name and options to the environment as the values
`handler` and `handler_opts` respectively.
Environment input:
* dispatch = dispatch_rules()
Environment output:
* handler = module()
* handler_opts = any()
:: Types
: bindings() = [{atom(), binary()}]
List of bindings found during routing.
: constraints() = [IntConstraint | FunConstraint]
Types:
* IntConstraint = {atom(), int}
* FunConstraint = {atom(), function, Fun}
* Fun = fun((binary()) -> true | {true, any()} | false)
List of constraints to apply to the bindings.
The int constraint will convert the binding to an integer.
The fun constraint allows writing custom code for checking
the bindings. Returning a new value from that fun allows
replacing the current binding with a new value.
: dispatch_rules() - opaque to the user
Rules for dispatching request used by Cowboy.
: routes() = [{Host, Paths} | {Host, constraints(), Paths}]
Types:
* Host = Path = '_' | iodata()
* Paths = [{Path, Handler, Opts} | {Path, constraints(), Handler, Opts}]
* Handler = module()
* Opts = any()
Human readable list of routes mapping hosts and paths to handlers.
The syntax for routes is defined in the user guide.
: tokens() = [binary()]
List of host_info and path_info tokens found during routing.
:: Exports
: compile(Routes) -> Dispatch
Types:
* Routes = routes()
* Dispatch = dispatch_rules()
Compile the routes for use by Cowboy.

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::: cowboy_spdy
The `cowboy_spdy` module implements SPDY/3 as a Ranch protocol.
:: Types
: opts() = [{env, cowboy_middleware:env()}
| {middlewares, [module()]}
| {onrequest, cowboy:onrequest_fun()}
| {onresponse, cowboy:onresponse_fun()}]
Configuration for the SPDY protocol handler.
This configuration is passed to Cowboy when starting listeners
using the `cowboy:start_spdy/4` function.
It can be updated without restarting listeners using the
Ranch functions `ranch:get_protocol_options/1` and
`ranch:set_protocol_options/2`.
:: Option descriptions
The default value is given next to the option name.
: env ([{listener, Ref}])
Initial middleware environment.
: middlewares ([cowboy_router, cowboy_handler])
List of middlewares to execute for every requests.
: onrequest (undefined)
Fun called every time a request is received.
: onresponse (undefined)
Fun called every time a response is sent.
:: Exports
None.

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::: cowboy_static
The `cowboy_static` module implements file serving capabilities
by using the REST semantics provided by `cowboy_rest`.
:: Types
: opts() = {priv_file, atom(), string() | binary()}
| {priv_file, atom(), string() | binary(), extra()}
| {file, string() | binary()}
| {file, string() | binary(), extra()}
| {priv_dir, atom(), string() | binary()}
| {priv_dir, atom(), string() | binary(), extra()}
| {dir, atom(), string() | binary()}
| {dir, atom(), string() | binary(), extra()}
Configuration for the static handler.
The handler can be configured for sending either one file or
a directory (including its subdirectories).
Extra options allow you to define how the etag should be calculated
and how the mimetype of files should be detected. They are defined
as follow, but do note that these types are not exported, only the
`opts/0` type is public.
: extra() = [extra_etag() | extra_mimetypes()]
: extra_etag() = {etag, module(), function()} | {etag, false}
: extra_mimetypes() = {mimetypes, module(), function()}
| {mimetypes, binary() | {binary(), binary(), [{binary(), binary()}]}}

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::: cowboy_sub_protocol
The `cowboy_sub_protocol` behaviour defines the interface used
by modules that implement a protocol on top of HTTP.
:: Types
None.
:: Callbacks
: upgrade(Req, Env, Handler, Opts)
-> {ok, Req, Env}
| {suspend, Module, Function, Args}
| {halt, Req}
| {error, StatusCode, Req}
Types:
* Req = cowboy_req:req()
* Env = env()
* Handler = module()
* Opts = any()
* Module = module()
* Function = atom()
* Args = [any()]
* StatusCode = cowboy:http_status()
Upgrade the protocol.
Please refer to the `cowboy_middleware` manual for a
description of the return values.

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::: cowboy_websocket
The `cowboy_websocket` module implements the Websocket protocol.
The callbacks for websocket handlers are defined in the manual
for the `cowboy_websocket_handler` behaviour.
:: Types
: close_code() = 1000..4999
Reason for closing the connection.
: frame() = close | ping | pong
| {text | binary | close | ping | pong, iodata()}
| {close, close_code(), iodata()}
Frames that can be sent to the client.
:: Meta values
: websocket_compress
Type: true | false
Whether a websocket compression extension in in use.
: websocket_version
Type: 7 | 8 | 13
The version of the Websocket protocol being used.
:: Exports
None.

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::: cowboy_websocket_handler
The `cowboy_websocket_handler` behaviour defines the interface used
by Websocket handlers.
The `init/3` and `websocket_init/3` callbacks will always be called,
followed by zero or more calls to `websocket_handle/3` and
`websocket_info/3`. The `websocket_terminate/3` will always
be called last.
:: Types
None.
:: Callbacks
: init({TransportName, ProtocolName}, Req, Opts)
-> {upgrade, protocol, cowboy_websocket}
| {upgrade, protocol, cowboy_websocket, Req, Opts}
Types:
* TransportName = tcp | ssl | atom()
* ProtocolName = http | atom()
* Req = cowboy_req:req()
* Opts = any()
Upgrade the protocol to `cowboy_websocket`.
: websocket_init(TransportName, Req, Opts)
-> {ok, Req, State}
| {ok, Req, State, hibernate}
| {ok, Req, State, Timeout}
| {ok, Req, State, Timeout, hibernate}
| {shutdown, Req}
Types:
* TransportName = tcp | ssl | atom()
* Req = cowboy_req:req()
* Opts = any()
* State = any()
* Timeout = timeout()
Initialize the state for this session.
This function is called before the upgrade to Websocket occurs.
It can be used to negotiate Websocket protocol extensions
with the client. It will typically be used to register this process
to an event manager or a message queue in order to receive
the messages the handler wants to process.
The connection will stay up for a duration of up to `Timeout`
milliseconds after it last received data from the socket,
at which point it will stop and close the connection.
By default this value is set to `infinity`. It is recommended
to either set this value or ensure by any other mechanism
that the handler will be closed after a certain period of
inactivity.
The `hibernate` option will hibernate the process until it
starts receiving either data from the Websocket connection
or Erlang messages.
The `shutdown` return value can be used to close the connection
before upgrading to Websocket.
: websocket_handle(InFrame, Req, State)
-> {ok, Req, State}
| {ok, Req, State, hibernate}
| {reply, OutFrame | [OutFrame], Req, State}
| {reply, OutFrame | [OutFrame], Req, State, hibernate}
| {shutdown, Req, State}
Types:
* InFrame = {text | binary | ping | pong, binary()}
* Req = cowboy_req:req()
* State = any()
* OutFrame = cowboy_websocket:frame()
Handle the data received from the Websocket connection.
This function will be called every time data is received
from the Websocket connection.
The `shutdown` return value can be used to close the
connection. A close reply will also result in the connection
being closed.
The `hibernate` option will hibernate the process until
it receives new data from the Websocket connection or an
Erlang message.
: websocket_info(Info, Req, State)
-> {ok, Req, State}
| {ok, Req, State, hibernate}
| {reply, OutFrame | [OutFrame], Req, State}
| {reply, OutFrame | [OutFrame], Req, State, hibernate}
| {shutdown, Req, State}
Types:
* Info = any()
* Req = cowboy_req:req()
* State = any()
* OutFrame = cowboy_websocket:frame()
Handle the Erlang message received.
This function will be called every time an Erlang message
has been received. The message can be any Erlang term.
The `shutdown` return value can be used to close the
connection. A close reply will also result in the connection
being closed.
The `hibernate` option will hibernate the process until
it receives another message or new data from the Websocket
connection.
: websocket_terminate(Reason, Req, State) -> ok
Types:
* Reason = {normal, shutdown | timeout} | {remote, closed} | {remote, cowboy_websocket:close_code(), binary()} | {error, badencoding | badframe | closed | atom()}
* Req = cowboy_req:req()
* State = any()
Perform any necessary cleanup of the state.
The connection will be closed and the process stopped right
after this call.

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HTTP status codes ::: HTTP status codes
=================
This chapter aims to list all HTTP status codes that Cowboy This chapter aims to list all HTTP status codes that Cowboy
may return, with details on the reasons why. The list given may return, with details on the reasons why. The list given
here only includes the replies that Cowboy sends, not user here only includes the replies that Cowboy sends, not user
replies. replies.
100 Continue : 100 Continue
------------
When the client sends an `expect: 100-continue` header, When the client sends an `expect: 100-continue` header,
Cowboy automatically sends a this status code before Cowboy automatically sends a this status code before
trying to read the request body. This behavior can be trying to read the request body. This behavior can be
disabled using the appropriate body option. disabled using the appropriate body option.
101 Switching Protocols : 101 Switching Protocols
-----------------------
This is the status code sent when switching to the This is the status code sent when switching to the
Websocket protocol. Websocket protocol.
200 OK : 200 OK
------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
201 Created : 201 Created
-----------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
202 Accepted : 202 Accepted
------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
204 No Content : 204 No Content
--------------
This status code is sent when the processing of a request This status code is sent when the processing of a request
ends without any reply having been sent. It may also be ends without any reply having been sent. It may also be
sent by `cowboy_rest` under normal conditions. sent by `cowboy_rest` under normal conditions.
300 Multiple Choices : 300 Multiple Choices
--------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
301 Moved Permanently : 301 Moved Permanently
---------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
303 See Other : 303 See Other
-------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
304 Not Modified : 304 Not Modified
----------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
307 Temporary Redirect : 307 Temporary Redirect
----------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
400 Bad Request : 400 Bad Request
---------------
Cowboy will send this status code for any of the Cowboy will send this status code for any of the
following reasons: following reasons:
@ -86,94 +73,78 @@ following reasons:
* REST under normal conditions. * REST under normal conditions.
* A Websocket upgrade failed. * A Websocket upgrade failed.
401 Unauthorized : 401 Unauthorized
----------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
403 Forbidden : 403 Forbidden
-------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
404 Not Found : 404 Not Found
-------------
This status code is sent when the router successfully This status code is sent when the router successfully
resolved the host but didn't find a matching path for resolved the host but didn't find a matching path for
the request. It may also be sent by `cowboy_rest` under the request. It may also be sent by `cowboy_rest` under
normal conditions. normal conditions.
405 Method Not Allowed : 405 Method Not Allowed
----------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
406 Not Acceptable : 406 Not Acceptable
------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
408 Request Timeout : 408 Request Timeout
-------------------
Cowboy will send this status code to the client if the Cowboy will send this status code to the client if the
client started to send a request, indicated by the client started to send a request, indicated by the
request-line being received fully, but failed to send request-line being received fully, but failed to send
all headers in a reasonable time. all headers in a reasonable time.
409 Conflict : 409 Conflict
------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
410 Gone : 410 Gone
--------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
412 Precondition Failed : 412 Precondition Failed
-----------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
413 Request Entity Too Large : 413 Request Entity Too Large
----------------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
414 Request-URI Too Long : 414 Request-URI Too Long
------------------------
Cowboy will send this status code to the client if the Cowboy will send this status code to the client if the
request-line is too long. It may also be sent by request-line is too long. It may also be sent by
`cowboy_rest` under normal conditions. `cowboy_rest` under normal conditions.
415 Unsupported Media Type : 415 Unsupported Media Type
--------------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
500 Internal Server Error : 500 Internal Server Error
-------------------------
This status code is sent when a crash occurs in HTTP, loop This status code is sent when a crash occurs in HTTP, loop
or REST handlers, or when an invalid return value is or REST handlers, or when an invalid return value is
returned. It may also be sent by `cowboy_rest` under returned. It may also be sent by `cowboy_rest` under
normal conditions. normal conditions.
501 Not Implemented : 501 Not Implemented
-------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
503 Service Unavailable : 503 Service Unavailable
-----------------------
This status code is sent by `cowboy_rest`. This status code is sent by `cowboy_rest`.
505 HTTP Version Not Supported : 505 HTTP Version Not Supported
------------------------------
Cowboy only supports the versions 1.0 and 1.1 of HTTP. Cowboy only supports the versions 1.0 and 1.1 of HTTP.
In all other cases this status code is sent back to the In all other cases this status code is sent back to the

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::: Cowboy Function Reference
The function reference documents the public interface of Cowboy.
* ^"The Cowboy Application^cowboy_app
* ^cowboy
* ^cowboy_handler
* ^cowboy_http_handler
* ^cowboy_loop_handler
* ^cowboy_middleware
* ^cowboy_protocol
* ^cowboy_req
* ^cowboy_rest
* ^cowboy_router
* ^cowboy_spdy
* ^cowboy_static
* ^cowboy_sub_protocol
* ^cowboy_websocket
* ^cowboy_websocket_handler
* ^"HTTP status codes^http_status_codes

11
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@ -199,17 +199,6 @@ clean-deps:
fi ; \ fi ; \
done done
# Documentation.
EDOC_OPTS ?=
docs: clean-docs
$(gen_verbose) erl -noshell \
-eval 'edoc:application($(PROJECT), ".", [$(EDOC_OPTS)]), init:stop().'
clean-docs:
$(gen_verbose) rm -f doc/*.css doc/*.html doc/*.png doc/edoc-info
# Tests. # Tests.
$(foreach dep,$(TEST_DEPS),$(eval $(call dep_target,$(dep)))) $(foreach dep,$(TEST_DEPS),$(eval $(call dep_target,$(dep))))

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Cowboy User Guide
=================
The Cowboy User Guide explores the modern Web and how to make
best use of Cowboy for writing powerful web applications.
Introducing Cowboy
------------------
* [Introduction](introduction.md)
* [The modern Web](modern_web.md)
* [Erlang and the Web](erlang_web.md)
* [Erlang for beginners](erlang_beginners.md)
* [Getting started](getting_started.md)
HTTP
----
* [The life of a request](http_req_life.md)
* [Routing](routing.md)
* [Handling plain HTTP requests](http_handlers.md)
* [The Req object](req.md)
* [Reading the request body](req_body.md)
* [Sending a response](resp.md)
* [Using cookies](cookies.md)
Multipart
---------
* [Introduction to multipart](multipart_intro.md)
* [Multipart requests](multipart_req.md)
Static files
------------
* [Static handler](static_handlers.md)
REST
----
* [REST principles](rest_principles.md)
* [Handling REST requests](rest_handlers.md)
* [REST flowcharts](rest_flowcharts.md)
* [Designing a resource handler](resource_design.md)
Websocket
---------
* [The Websocket protocol](ws_protocol.md)
* [Handling Websocket connections](ws_handlers.md)
Server push
-----------
* [Loop handlers](loop_handlers.md)
Pluggable interface
-------------------
* [Middlewares](middlewares.md)
* [Protocol upgrades](upgrade_protocol.md)
* [Hooks](hooks.md)
Internals
---------
* [Architecture](architecture.md)
* [Dealing with broken clients](broken_clients.md)

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cowboy
======
The `cowboy` module provides convenience functions for
manipulating Ranch listeners.
Types
-----
### http_headers() = [{binary(), iodata()}]
> HTTP headers as a list of key/values.
### http_status() = non_neg_integer() | binary()
> HTTP status.
>
> A binary status can be used to set a custom message.
### http_version() = 'HTTP/1.1' | 'HTTP/1.0'
> HTTP version.
### onrequest_fun() = fun((cowboy_req:req()) -> cowboy_req:req())
> Fun called immediately after receiving a request.
>
> It can perform any operation on the `Req` object, including
> reading the request body or replying. If a reply is sent,
> the processing of the request ends here, before any middleware
> is executed.
### onresponse_fun() = fun((http_status(), http_headers(),
iodata(), cowboy_req:req()) -> cowboy_req:req())
> Fun called immediately before sending the response.
>
> It can perform any operation on the `Req` object, including
> reading the request body or replying. If a reply is sent, it
> overrides the reply initially sent. The callback will not be
> called again for the new reply.
Exports
-------
### start_http(Ref, NbAcceptors, TransOpts, ProtoOpts) -> {ok, pid()}
> Types:
> * Ref = ranch:ref()
> * NbAcceptors = non_neg_integer()
> * TransOpts = ranch_tcp:opts()
> * ProtoOpts = cowboy_protocol:opts()
>
> Start listening for HTTP connections. Returns the pid for this
> listener's supervisor.
### start_https(Ref, NbAcceptors, TransOpts, ProtoOpts) -> {ok, pid()}
> Types:
> * Ref = ranch:ref()
> * NbAcceptors = non_neg_integer()
> * TransOpts = ranch_ssl:opts()
> * ProtoOpts = cowboy_protocol:opts()
>
> Start listening for HTTPS connections. Returns the pid for this
> listener's supervisor.
### start_spdy(Ref, NbAcceptors, TransOpts, ProtoOpts) -> {ok, pid()}
> Types:
> * Ref = ranch:ref()
> * NbAcceptors = non_neg_integer()
> * TransOpts = ranch_ssl:opts()
> * ProtoOpts = cowboy_spdy:opts()
>
> Start listening for SPDY connections. Returns the pid for this
> listener's supervisor.
### stop_listener(Ref) -> ok | {error, not_found}
> Types:
> * Ref = ranch:ref()
>
> Stop a previously started listener.
### set_env(Ref, Name, Value) -> ok
> Types:
> * Ref = ranch:ref()
> * Name = atom()
> * Value = any()
>
> Set or update an environment value for an already running listener.
> This will take effect on all subsequent connections.
See also
--------
The [Ranch guide](http://ninenines.eu/docs/en/ranch/HEAD/guide)
provides detailed information about how listeners work.

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cowboy_http_handler
===================
The `cowboy_http_handler` behaviour defines the interface used
by plain HTTP handlers.
Unless noted otherwise, the callbacks will be executed sequentially.
Types
-----
None.
Callbacks
---------
### init({TransportName, ProtocolName}, Req, Opts)
-> {ok, Req, State} | {shutdown, Req, State}
> Types:
> * TransportName = tcp | ssl | atom()
> * ProtocolName = http | atom()
> * Req = cowboy_req:req()
> * Opts = any()
> * State = any()
>
> Initialize the state for this request.
>
> The `shutdown` return value can be used to skip the `handle/2`
> call entirely.
### handle(Req, State) -> {ok, Req, State}
> Types:
> * Req = cowboy_req:req()
> * State = any()
>
> Handle the request.
>
> This callback is where the request is handled and a response
> should be sent. If a response is not sent, Cowboy will send
> a `204 No Content` response automatically.
### terminate(Reason, Req, State) -> ok
> Types:
> * Reason = {normal, shutdown} | {error, atom()}
> * Req = cowboy_req:req()
> * State = any()
>
> Perform any necessary cleanup of the state.
>
> This callback should release any resource currently in use,
> clear any active timer and reset the process to its original
> state, as it might be reused for future requests sent on the
> same connection. Typical plain HTTP handlers rarely need to
> use it.

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cowboy_loop_handler
===================
The `cowboy_loop_handler` behaviour defines the interface used
by HTTP handlers that do not send a response directly, instead
requiring a receive loop to process Erlang messages.
This interface is best fit for long-polling types of requests.
The `init/3` callback will always be called, followed by zero
or more calls to `info/3`. The `terminate/3` will always be
called last.
Types
-----
None.
Callbacks
---------
### init({TransportName, ProtocolName}, Req, Opts)
-> {loop, Req, State}
| {loop, Req, State, hibernate}
| {loop, Req, State, Timeout}
| {loop, Req, State, Timeout, hibernate}
| {shutdown, Req, State}
> Types:
> * TransportName = tcp | ssl | atom()
> * ProtocolName = http | atom()
> * Req = cowboy_req:req()
> * Opts = any()
> * State = any()
> * Timeout = timeout()
>
> Initialize the state for this request.
>
> This callback will typically be used to register this process
> to an event manager or a message queue in order to receive
> the messages the handler wants to process.
>
> The receive loop will run for a duration of up to `Timeout`
> milliseconds after it last received data from the socket,
> at which point it will stop and send a `204 No Content` reply.
> By default this value is set to `infinity`. It is recommended
> to either set this value or ensure by any other mechanism
> that the handler will be closed after a certain period of
> inactivity.
>
> The `hibernate` option will hibernate the process until it
> starts receiving messages.
>
> The `shutdown` return value can be used to skip the receive
> loop entirely.
### info(Info, Req, State) -> {ok, Req, State} | {loop, Req, State}
| {loop, Req, State, hibernate}
> Types:
> * Info = any()
> * Req = cowboy_req:req()
> * State = any()
>
> Handle the Erlang message received.
>
> This function will be called every time an Erlang message
> has been received. The message can be any Erlang term.
>
> The `ok` return value can be used to stop the receive loop,
> typically because a response has been sent.
>
> The `hibernate` option will hibernate the process until
> it receives another message.
### terminate(Reason, Req, State) -> ok
> Types:
> * Reason = {normal, shutdown} | {normal, timeout} | {error, closed} | {error, overflow} | {error, atom()}
> * Req = cowboy_req:req()
> * State = any()
>
> Perform any necessary cleanup of the state.
>
> This callback will typically unregister from any event manager
> or message queue it registered to in `init/3`.
>
> This callback should release any resource currently in use,
> clear any active timer and reset the process to its original
> state, as it might be reused for future requests sent on the
> same connection.

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cowboy_middleware
=================
The `cowboy_middleware` behaviour defines the interface used
by Cowboy middleware modules.
Middlewares process the request sequentially in the order they
are configured.
Types
-----
### env() = [{atom(), any()}]
> The environment variable.
>
> One is created for every request. It is passed to each
> middleware module executed and subsequently returned,
> optionally with its contents modified.
Callbacks
---------
### execute(Req, Env)
-> {ok, Req, Env}
| {suspend, Module, Function, Args}
| {halt, Req}
| {error, StatusCode, Req}
> Types:
> * Req = cowboy_req:req()
> * Env = env()
> * Module = module()
> * Function = atom()
> * Args = [any()]
> * StatusCode = cowboy:http_status()
>
> Execute the middleware.
>
> The `ok` return value indicates that everything went well
> and that Cowboy should continue processing the request. A
> response may or may not have been sent.
>
> The `suspend` return value will hibernate the process until
> an Erlang message is received. Note that when resuming, any
> previous stacktrace information will be gone.
>
> The `halt` return value stops Cowboy from doing any further
> processing of the request, even if there are middlewares
> that haven't been executed yet. The connection may be left
> open to receive more requests from the client.
>
> The `error` return value sends an error response identified
> by the `StatusCode` and then proceeds to terminate the
> connection. Middlewares that haven't been executed yet
> will not be called.

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cowboy_protocol
===============
The `cowboy_protocol` module implements HTTP/1.1 and HTTP/1.0
as a Ranch protocol.
Types
-----
### opts() = [{compress, boolean()}
| {env, cowboy_middleware:env()}
| {max_empty_lines, non_neg_integer()}
| {max_header_name_length, non_neg_integer()}
| {max_header_value_length, non_neg_integer()}
| {max_headers, non_neg_integer()}
| {max_keepalive, non_neg_integer()}
| {max_request_line_length, non_neg_integer()}
| {middlewares, [module()]}
| {onrequest, cowboy:onrequest_fun()}
| {onresponse, cowboy:onresponse_fun()}
| {timeout, timeout()}]
> Configuration for the HTTP protocol handler.
>
> This configuration is passed to Cowboy when starting listeners
> using `cowboy:start_http/4` or `cowboy:start_https/4` functions.
>
> It can be updated without restarting listeners using the
> Ranch functions `ranch:get_protocol_options/1` and
> `ranch:set_protocol_options/2`.
Option descriptions
-------------------
The default value is given next to the option name.
- compress (false)
- When enabled, Cowboy will attempt to compress the response body.
- env ([{listener, Ref}])
- Initial middleware environment.
- max_empty_lines (5)
- Maximum number of empty lines before a request.
- max_header_name_length (64)
- Maximum length of header names.
- max_header_value_length (4096)
- Maximum length of header values.
- max_headers (100)
- Maximum number of headers allowed per request.
- max_keepalive (100)
- Maximum number of requests allowed per connection.
- max_request_line_length (4096)
- Maximum length of the request line.
- middlewares ([cowboy_router, cowboy_handler])
- List of middlewares to execute for every requests.
- onrequest (undefined)
- Fun called every time a request is received.
- onresponse (undefined)
- Fun called every time a response is sent.
- timeout (5000)
- Time in ms with no requests before Cowboy closes the connection.
Exports
-------
None.

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cowboy_req
==========
The `cowboy_req` module provides functions to access, manipulate
and respond to requests.
The functions in this module follow patterns for their return types,
based on the kind of function.
* access: `{Value, Req}`
* action: `{Result, Req} | {Result, Value, Req} | {error, atom()}`
* modification: `Req`
* question: `boolean()`
The only exception is the `chunk/2` function which may return `ok`.
Whenever `Req` is returned, you must use this returned value and
ignore any previous you may have had. This value contains various
state informations which are necessary for Cowboy to do some lazy
evaluation or cache results where appropriate.
All functions which perform an action should only be called once.
This includes reading the request body or replying. Cowboy will
generally throw an error on the second call.
It is highly discouraged to pass the Req object to another process.
Doing so and calling `cowboy_req` functions from it leads to
undefined behavior.
Types
-----
### body_opts() = [{continue, boolean()}
| {length, non_neg_integer()}
| {read_length, non_neg_integer()}
| {read_timeout, timeout()}
| {transfer_decode, transfer_decode_fun(), any()}
| {content_decode, content_decode_fun()}]
> Request body reading options.
### cookie_opts() = [{max_age, non_neg_integer()}
| {domain, binary()} | {path, binary()}
| {secure, boolean()} | {http_only, boolean()}]
> Cookie options.
### req() - opaque to the user
> The `Req` object.
>
> All functions in this module receive a `Req` as argument,
> and most of them return a new object labelled `Req2` in
> the function descriptions below.
Request related exports
-----------------------
### binding(Name, Req) -> binding(Name, Req, undefined)
### binding(Name, Req, Default) -> {Value, Req2}
> Types:
> * Name = atom()
> * Default = any()
> * Value = any() | Default
>
> Return the value for the given binding.
>
> By default the value is a binary, however constraints may change
> the type of this value (for example automatically converting
> numbers to integer).
### bindings(Req) -> {[{Name, Value}], Req2}
> Types:
> * Name = atom()
> * Value = any()
>
> Return all bindings.
>
> By default the value is a binary, however constraints may change
> the type of this value (for example automatically converting
> numbers to integer).
### cookie(Name, Req) -> cookie(Name, Req, undefined)
### cookie(Name, Req, Default) -> {Value, Req2}
> Types:
> * Name = binary()
> * Default = any()
> * Value = binary() | Default
>
> Return the value for the given cookie.
>
> Cookie names are case sensitive.
### cookies(Req) -> {[{Name, Value}], Req2}
> Types:
> * Name = binary()
> * Value = binary()
>
> Return all cookies.
### header(Name, Req) -> header(Name, Req, undefined)
### header(Name, Req, Default) -> {Value, Req2}
> Types:
> * Name = binary()
> * Default = any()
> * Value = binary() | Default
>
> Return the value for the given header.
>
> While header names are case insensitive, this function expects
> the name to be a lowercase binary.
### headers(Req) -> {Headers, Req2}
> Types:
> * Headers = cowboy:http_headers()
>
> Return all headers.
### host(Req) -> {Host, Req2}
> Types:
> * Host = binary()
>
> Return the requested host.
### host_info(Req) -> {HostInfo, Req2}
> Types:
> * HostInfo = cowboy_router:tokens() | undefined
>
> Return the extra tokens from matching against `...` during routing.
### host_url(Req) -> {HostURL, Req2}
> Types:
> * HostURL = binary() | undefined
>
> Return the requested URL excluding the path component.
>
> This function will always return `undefined` until the
> `cowboy_router` middleware has been executed. This includes
> the `onrequest` hook.
### meta(Name, Req) -> meta(Name, Req, undefined)
### meta(Name, Req, Default) -> {Value, Req2}
> Types:
> * Name = atom()
> * Default = any()
> * Value = any()
>
> Return metadata about the request.
### method(Req) -> {Method, Req2}
> Types:
> * Method = binary()
>
> Return the method.
>
> Methods are case sensitive. Standard methods are always uppercase.
### parse_header(Name, Req) ->
### parse_header(Name, Req, Default) -> {ok, ParsedValue, Req2}
| {undefined, Value, Req2} | {error, badarg}
> Types:
> * Name = binary()
> * Default = any()
> * ParsedValue - see below
> * Value = any()
>
> Parse the given header.
>
> While header names are case insensitive, this function expects
> the name to be a lowercase binary.
>
> The `parse_header/2` function will call `parser_header/3` with a
> different default value depending on the header being parsed. The
> following table summarizes the default values used.
>
> | Header name | Default value |
> | ----------------- | ------------------ |
> | transfer-encoding | `[<<"identity">>]` |
> | Any other header | `undefined` |
>
> The parsed value differs depending on the header being parsed. The
> following table summarizes the different types returned.
>
> | Header name | Type |
> | ---------------------- | ------------------------------------------------- |
> | accept | `[{{Type, SubType, Params}, Quality, AcceptExt}]` |
> | accept-charset | `[{Charset, Quality}]` |
> | accept-encoding | `[{Encoding, Quality}]` |
> | accept-language | `[{LanguageTag, Quality}]` |
> | authorization | `{AuthType, Credentials}` |
> | content-length | `non_neg_integer()` |
> | content-type | `{Type, SubType, ContentTypeParams}` |
> | cookie | `[{binary(), binary()}]` |
> | expect | `[Expect | {Expect, ExpectValue, Params}]` |
> | if-match | `'*' | [{weak | strong, OpaqueTag}]` |
> | if-modified-since | `calendar:datetime()` |
> | if-none-match | `'*' | [{weak | strong, OpaqueTag}]` |
> | if-unmodified-since | `calendar:datetime()` |
> | range | `{Unit, [Range]}` |
> | sec-websocket-protocol | `[binary()]` |
> | transfer-encoding | `[binary()]` |
> | upgrade | `[binary()]` |
> | x-forwarded-for | `[binary()]` |
>
> Types for the above table:
> * Type = SubType = Charset = Encoding = LanguageTag = binary()
> * AuthType = Expect = OpaqueTag = Unit = binary()
> * Params = ContentTypeParams = [{binary(), binary()}]
> * Quality = 0..1000
> * AcceptExt = [{binary(), binary()} | binary()]
> * Credentials - see below
> * Range = {non_neg_integer(), non_neg_integer() | infinity} | neg_integer()
>
> The cookie names and values, the values of the sec-websocket-protocol
> and x-forwarded-for headers, the values in `AcceptExt` and `Params`,
> the authorization `Credentials`, the `ExpectValue` and `OpaqueTag`
> are case sensitive. All values in `ContentTypeParams` are case sensitive
> except the value of the charset parameter, which is case insensitive.
> All other values are case insensitive and will be returned as lowercase.
>
> The headers accept, accept-encoding and cookie headers can return
> an empty list. Others will return `{error, badarg}` if the header
> value is empty.
>
> The authorization header parsing code currently only supports basic
> HTTP authentication. The `Credentials` type is thus `{Username, Password}`
> with `Username` and `Password` being `binary()`.
>
> The range header value `Range` can take three forms:
> * `{From, To}`: from `From` to `To` units
> * `{From, infinity}`: everything after `From` units
> * `-Final`: the final `Final` units
>
> An `undefined` tuple will be returned if Cowboy doesn't know how
> to parse the requested header.
### path(Req) -> {Path, Req2}
> Types:
> * Path = binary()
>
> Return the requested path.
### path_info(Req) -> {PathInfo, Req2}
> Types:
> * PathInfo = cowboy_router:tokens() | undefined
>
> Return the extra tokens from matching against `...` during routing.
### peer(Req) -> {Peer, Req2}
> Types:
> * Peer = {inet:ip_address(), inet:port_number()}
>
> Return the client's IP address and port number.
### port(Req) -> {Port, Req2}
> Types:
> * Port = inet:port_number()
>
> Return the request's port.
>
> The port returned by this function is obtained by parsing
> the host header. It may be different than the actual port
> the client used to connect to the Cowboy server.
### qs(Req) -> {QueryString, Req2}
> Types:
> * QueryString = binary()
>
> Return the request's query string.
### qs_val(Name, Req) -> qs_val(Name, Req, undefined)
### qs_val(Name, Req, Default) -> {Value, Req2}
> Types:
> * Name = binary()
> * Default = any()
> * Value = binary() | true
>
> Return a value from the request's query string.
>
> The value `true` will be returned when the name was found
> in the query string without an associated value.
### qs_vals(Req) -> {[{Name, Value}], Req2}
> Types:
> * Name = binary()
> * Value = binary() | true
>
> Return the request's query string as a list of tuples.
>
> The value `true` will be returned when a name was found
> in the query string without an associated value.
### set_meta(Name, Value, Req) -> Req2
> Types:
> * Name = atom()
> * Value = any()
>
> Set metadata about the request.
>
> An existing value will be overwritten.
### url(Req) -> {URL, Req2}
> Types:
> * URL = binary() | undefined
>
> Return the requested URL.
>
> This function will always return `undefined` until the
> `cowboy_router` middleware has been executed. This includes
> the `onrequest` hook.
### version(Req) -> {Version, Req2}
> Types:
> * Version = cowboy:http_version()
>
> Return the HTTP version used for this request.
Request body related exports
----------------------------
### body(Req) -> body(Req, [])
### body(Req, Opts) -> {ok, Data, Req2} | {more, Data, Req2} | {error, Reason}
> Types:
> * Opts = [body_opt()]
> * Data = binary()
> * Reason = atom()
>
> Read the request body.
>
> This function will read a chunk of the request body. If there is
> more data to be read after this function call, then a `more` tuple
> is returned. Otherwise an `ok` tuple is returned.
>
> Cowboy will automatically send a `100 Continue` reply if
> required. If this behavior is not desirable, it can be disabled
> by setting the `continue` option to `false`.
>
> Cowboy will by default attempt to read up to 8MB of the body,
> but in chunks of 1MB. It will use a timeout of 15s per chunk.
> All these values can be changed using the `length`, `read_length`
> and `read_timeout` options respectively. Note that the size
> of the data may not be the same as requested as the decoding
> functions may grow or shrink it, and Cowboy makes not attempt
> at returning an exact amount.
>
> Cowboy will properly handle chunked transfer-encoding by
> default. If any other transfer-encoding or content-encoding
> has been used for the request, custom decoding functions
> can be used. The `content_decode` and `transfer_decode`
> options allow setting the decode functions manually.
>
> After the body has been streamed fully, Cowboy will remove
> the transfer-encoding header from the `Req` object, and add
> the content-length header if it wasn't already there.
>
> This function can only be called once. Cowboy will not cache
> the result of this call.
### body_length(Req) -> {Length, Req2}
> Types:
> * Length = non_neg_integer() | undefined
>
> Return the length of the request body.
>
> The length will only be returned if the request does not
> use any transfer-encoding and if the content-length header
> is present.
### body_qs(Req) -> body_qs(Req,
[{length, 64000}, {read_length, 64000}, {read_timeout, 5000}])
### body_qs(Req, Opts) -> {ok, [{Name, Value}], Req2}
| {badlength, Req2} | {error, Reason}
> Types:
> * Opts = [body_opt()]
> * Name = binary()
> * Value = binary() | true
> * Reason = chunked | badlength | atom()
>
> Return the request body as a list of tuples.
>
> This function will parse the body assuming the content-type
> application/x-www-form-urlencoded, commonly used for the
> query string.
>
> This function calls `body/2` for reading the body, with the
> same options it received. By default it will attempt to read
> a body of 64KB in one chunk, with a timeout of 5s. If the
> body is larger then a `badlength` tuple is returned.
>
> This function can only be called once. Cowboy will not cache
> the result of this call.
### has_body(Req) -> boolean()
> Return whether the request has a body.
### part(Req) -> part(Req,
[{length, 64000}, {read_length, 64000}, {read_timeout, 5000}])
### part(Req, Opts) -> {ok, Headers, Req2} | {done, Req2}
> Types:
> * Opts = [body_opt()]
> * Headers = cow_multipart:headers()
>
> Read the headers for the next part of the multipart message.
>
> Cowboy will skip any data remaining until the beginning of
> the next part. This includes the preamble to the multipart
> message but also the body of a previous part if it hasn't
> been read. Both are skipped automatically when calling this
> function.
>
> The headers returned are MIME headers, NOT HTTP headers.
> They can be parsed using the functions from the `cow_multipart`
> module. In addition, the `cow_multipart:form_data/1` function
> can be used to quickly figure out `multipart/form-data` messages.
> It takes the list of headers and returns whether this part is
> a simple form field or a file being uploaded.
>
> Note that once a part has been read, or skipped, it cannot
> be read again.
>
> This function calls `body/2` for reading the body, with the
> same options it received. By default it will only read chunks
> of 64KB with a timeout of 5s. This is tailored for reading
> part headers, not for skipping the previous part's body.
> You might want to consider skipping large parts manually.
### part_body(Req) -> part_body(Req, [])
### part_body(Req, Opts) -> {ok, Data, Req2} | {more, Data, Req2}
> Types:
> * Opts = [body_opt()]
> * Data = binary()
>
> Read the body of the current part of the multipart message.
>
> This function calls `body/2` for reading the body, with the
> same options it received. It uses the same defaults.
>
> If there are more data to be read from the socket for this
> part, the function will return what it could read inside a
> `more` tuple. Otherwise, it will return an `ok` tuple.
>
> Calling this function again after receiving a `more` tuple
> will return another chunk of body. The last chunk will be
> returned inside an `ok` tuple.
>
> Note that once the body has been read, fully or partially,
> it cannot be read again.
Response related exports
------------------------
### chunk(Data, Req) -> ok | {error, Reason}
> Types:
> * Data = iodata()
> * Reason = atom()
>
> Send a chunk of data.
>
> This function should be called as many times as needed
> to send data chunks after calling `chunked_reply/{2,3}`.
>
> When the method is HEAD, no data will actually be sent.
>
> If the request uses HTTP/1.0, the data is sent directly
> without wrapping it in an HTTP/1.1 chunk, providing
> compatibility with older clients.
### chunked_reply(StatusCode, Req) -> chunked_reply(StatusCode, [], Req)
### chunked_reply(StatusCode, Headers, Req) -> {ok, Req2}
> Types:
> * StatusCode = cowboy:http_status()
> * Headers = cowboy:http_headers()
>
> Send a response using chunked transfer-encoding.
>
> This function effectively sends the response status line
> and headers to the client.
>
> This function will not send any body set previously. After
> this call the handler must use the `chunk/2` function
> repeatedly to send the body in as many chunks as needed.
>
> If the request uses HTTP/1.0, the data is sent directly
> without wrapping it in an HTTP/1.1 chunk, providing
> compatibility with older clients.
>
> This function can only be called once, with the exception
> of overriding the response in the `onresponse` hook.
### continue(Req) -> ok | {error, Reason}
> Types:
> * Reason = atom()
>
> Send a 100 Continue intermediate reply.
>
> This reply is required before the client starts sending the
> body when the request contains the `expect` header with the
> `100-continue` value.
>
> Cowboy will send this automatically when required. However
> you may want to do it manually by disabling this behavior
> with the `continue` body option and then calling this
> function.
### delete_resp_header(Name, Req) -> Req2
> Types:
> * Name = binary()
>
> Delete the given response header.
>
> While header names are case insensitive, this function expects
> the name to be a lowercase binary.
### has_resp_body(Req) -> boolean()
> Return whether a response body has been set.
>
> This function will return false if a response body has
> been set with a length of 0.
### has_resp_header(Name, Req) -> boolean()
> Types:
> * Name = binary()
>
> Return whether the given response header has been set.
>
> While header names are case insensitive, this function expects
> the name to be a lowercase binary.
### reply(StatusCode, Req) -> reply(StatusCode, [], Req)
### reply(StatusCode, Headers, Req) - see below
### reply(StatusCode, Headers, Body, Req) -> {ok, Req2}
> Types:
> * StatusCode = cowboy:http_status()
> * Headers = cowboy:http_headers()
> * Body = iodata()
>
> Send a response.
>
> This function effectively sends the response status line,
> headers and body to the client, in a single send function
> call.
>
> The `reply/2` and `reply/3` functions will send the body
> set previously, if any. The `reply/4` function overrides
> any body set previously and sends `Body` instead.
>
> If a body function was set, and `reply/2` or `reply/3` was
> used, it will be called before returning.
>
> No more data can be sent to the client after this function
> returns.
>
> This function can only be called once, with the exception
> of overriding the response in the `onresponse` hook.
### set_resp_body(Body, Req) -> Req2
> Types:
> * Body = iodata()
>
> Set a response body.
>
> This body will not be sent if `chunked_reply/{2,3}` or
> `reply/4` is used, as they override it.
### set_resp_body_fun(Fun, Req) -> Req2
### set_resp_body_fun(Length, Fun, Req) -> Req2
> Types:
> * Fun = fun((Socket, Transport) -> ok)
> * Socket = inet:socket()
> * Transport = module()
> * Length = non_neg_integer()
>
> Set a fun for sending the response body.
>
> If a `Length` is provided, it will be sent in the
> content-length header in the response. It is recommended
> to set the length if it can be known in advance. Otherwise,
> the transfer-encoding header will be set to identity.
>
> This function will only be called if the response is sent
> using the `reply/2` or `reply/3` function.
>
> The fun will receive the Ranch `Socket` and `Transport` as
> arguments. Only send and sendfile operations are supported.
### set_resp_body_fun(chunked, Fun, Req) -> Req2
> Types:
> * Fun = fun((ChunkFun) -> ok)
> * ChunkFun = fun((iodata()) -> ok | {error, atom()})
>
> Set a fun for sending the response body using chunked transfer-encoding.
>
> This function will only be called if the response is sent
> using the `reply/2` or `reply/3` function.
>
> The fun will receive another fun as argument. This fun is to
> be used to send chunks in a similar way to the `chunk/2` function,
> except the fun only takes one argument, the data to be sent in
> the chunk.
### set_resp_cookie(Name, Value, Opts, Req) -> Req2
> Types:
> * Name = iodata()
> * Value = iodata()
> * Opts = cookie_opts()
>
> Set a cookie in the response.
>
> Cookie names are case sensitive.
### set_resp_header(Name, Value, Req) -> Req2
> Types:
> * Name = binary()
> * Value = iodata()
>
> Set a response header.
>
> You should use `set_resp_cookie/4` instead of this function
> to set cookies.
Misc. exports
-------------
### compact(Req) -> Req2
> Remove any non-essential data from the `Req` object.
>
> Long-lived connections usually only need to manipulate the
> `Req` object at initialization. Compacting allows saving up
> memory by discarding extraneous information.

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@ -1,560 +0,0 @@
cowboy_rest
===========
The `cowboy_rest` module implements REST semantics on top of
the HTTP protocol.
This module cannot be described as a behaviour due to most of
the callbacks it defines being optional. It has the same
semantics as a behaviour otherwise.
The only mandatory callback is `init/3`, needed to perform
the protocol upgrade.
Types
-----
None.
Meta values
-----------
### charset
> Type: binary()
>
> Negotiated charset.
>
> This value may not be defined if no charset was negotiated.
### language
> Type: binary()
>
> Negotiated language.
>
> This value may not be defined if no language was negotiated.
### media_type
> Type: {binary(), binary(), '*' | [{binary(), binary()}]}
>
> Negotiated media-type.
>
> The media-type is the content-type, excluding the charset.
>
> This value is always defined after the call to
> `content_types_provided/2`.
Callbacks
---------
### init({TransportName, ProtocolName}, Req, Opts)
-> {upgrade, protocol, cowboy_rest}
| {upgrade, protocol, cowboy_rest, Req, Opts}
> Types:
> * TransportName = tcp | ssl | atom()
> * ProtocolName = http | atom()
> * Req = cowboy_req:req()
> * Opts = any()
>
> Upgrade the protocol to `cowboy_rest`.
>
> This is the only mandatory callback.
### rest_init(Req, Opts) -> {ok, Req, State}
> Types:
> * Req = cowboy_req:req()
> * Opts = any()
> * State = any()
>
> Initialize the state for this request.
### rest_terminate(Req, State) -> ok
> Types:
> * Req = cowboy_req:req()
> * State = any()
>
> Perform any necessary cleanup of the state.
>
> This callback should release any resource currently in use,
> clear any active timer and reset the process to its original
> state, as it might be reused for future requests sent on the
> same connection.
### Callback(Req, State) -> {Value, Req, State} | {halt, Req, State}
> Types:
> * Callback - one of the REST callbacks described below
> * Req = cowboy_req:req()
> * State = any()
> * Value - see the REST callbacks description below
>
> Please see the REST callbacks description below for details
> on the `Value` type, the default value if the callback is
> not defined, and more general information on when the
> callback is called and what its intended use is.
>
> The `halt` tuple can be returned to stop REST processing.
> It is up to the resource code to send a reply before that,
> otherwise a `204 No Content` will be sent.
REST callbacks description
--------------------------
### allowed_methods
> * Methods: all
> * Value type: [binary()]
> * Default value: [<<"GET">>, <<"HEAD">>, <<"OPTIONS">>]
>
> Return the list of allowed methods.
>
> Methods are case sensitive. Standard methods are always uppercase.
### allow_missing_post
> * Methods: POST
> * Value type: boolean()
> * Default value: true
>
> Return whether POST is allowed when the resource doesn't exist.
>
> Returning `true` here means that a new resource will be
> created. The URL to the created resource should also be
> returned from the `AcceptResource` callback.
### charsets_provided
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Value type: [binary()]
> * Skip to the next step if undefined
>
> Return the list of charsets the resource provides.
>
> The list must be ordered in order of preference.
>
> If the accept-charset header was not sent, the first charset
> in the list will be selected. Otherwise Cowboy will select
> the most appropriate charset from the list.
>
> The chosen charset will be set in the `Req` object as the meta
> value `charset`.
>
> While charsets are case insensitive, this callback is expected
> to return them as lowercase binary.
### content_types_accepted
> * Methods: POST, PUT, PATCH
> * No default
>
> Types:
> * Value = [{binary() | {Type, SubType, Params}, AcceptResource}]
> * Type = SubType = binary()
> * Params = '*' | [{binary(), binary()}]
> * AcceptResource = atom()
>
> Return the list of content-types the resource accepts.
>
> The list must be ordered in order of preference.
>
> Each content-type can be given either as a binary string or as
> a tuple containing the type, subtype and parameters.
>
> Cowboy will select the most appropriate content-type from the list.
> If any parameter is acceptable, then the tuple form should be used
> with parameters set to `'*'`. If the parameters value is set to `[]`
> only content-type values with no parameters will be accepted. All
> parameter values are treated in a case sensitive manner except the
> `charset` parameter, if present, which is case insensitive.
>
> This function will be called for POST, PUT and PATCH requests.
> It is entirely possible to define different callbacks for different
> methods if the handling of the request differs. Simply verify
> what the method is with `cowboy_req:method/1` and return a
> different list for each methods.
>
> The `AcceptResource` value is the name of the callback that will
> be called if the content-type matches. It is defined as follow.
>
> * Value type: true | {true, URL} | false
> * No default
>
> Process the request body.
>
> This function should create or update the resource with the
> information contained in the request body. This information
> may be full or partial depending on the request method.
>
> If the request body was processed successfully, `true` or
> `{true, URL}` may be returned. If an URL is provided, the
> response will redirect the client to the location of the
> resource.
>
> If a response body must be sent, the appropriate media-type, charset
> and language can be retrieved using the `cowboy_req:meta/{2,3}`
> functions. The respective keys are `media_type`, `charset`
> and `language`. The body can be set using `cowboy_req:set_resp_body/2`.
### content_types_provided
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Default value: [{{<<"text">>, <<"html">>, '*'}, to_html}]
>
> Types:
> * Value = [{binary() | {Type, SubType, Params}, ProvideResource}]
> * Type = SubType = binary()
> * Params = '*' | [{binary(), binary()}]
> * ProvideResource = atom()
>
> Return the list of content-types the resource provides.
>
> The list must be ordered in order of preference.
>
> Each content-type can be given either as a binary string or as
> a tuple containing the type, subtype and parameters.
>
> Cowboy will select the most appropriate content-type from the list.
> If any parameter is acceptable, then the tuple form should be used
> with parameters set to `'*'`. If the parameters value is set to `[]`
> only content-type values with no parameters will be accepted. All
> parameter values are treated in a case sensitive manner except the
> `charset` parameter, if present, which is case insensitive.
>
> The `ProvideResource` value is the name of the callback that will
> be called if the content-type matches. It will only be called when
> a representation of the resource needs to be returned. It is defined
> as follow.
>
> * Methods: GET, HEAD
> * Value type: iodata() | {stream, Fun} | {stream, Len, Fun} | {chunked, ChunkedFun}
> * No default
>
> Return the response body.
>
> The response body may be provided directly or through a fun.
> If a fun tuple is returned, the appropriate `set_resp_body_fun`
> function will be called. Please refer to the documentation for
> these functions for more information about the types.
>
> The call to this callback happens a good time after the call to
> `content_types_provided/2`, when it is time to start rendering
> the response body.
### delete_completed
> * Methods: DELETE
> * Value type: boolean()
> * Default value: true
>
> Return whether the delete action has been completed.
>
> This function should return `false` if there is no guarantee
> that the resource gets deleted immediately from the system,
> including from any internal cache.
>
> When this function returns `false`, a `202 Accepted`
> response will be sent instead of a `200 OK` or `204 No Content`.
### delete_resource
> * Methods: DELETE
> * Value type: boolean()
> * Default value: false
>
> Delete the resource.
>
> The value returned indicates if the action was successful,
> regardless of whether the resource is immediately deleted
> from the system.
### expires
> * Methods: GET, HEAD
> * Value type: calendar:datetime() | binary() | undefined
> * Default value: undefined
>
> Return the date of expiration of the resource.
>
> This date will be sent as the value of the expires header.
### forbidden
> * Methods: all
> * Value type: boolean()
> * Default value: false
>
> Return whether access to the resource is forbidden.
>
> A `403 Forbidden` response will be sent if this
> function returns `true`. This status code means that
> access is forbidden regardless of authentication,
> and that the request shouldn't be repeated.
### generate_etag
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Value type: binary() | {weak | strong, binary()}
> * Default value: undefined
>
> Return the entity tag of the resource.
>
> This value will be sent as the value of the etag header.
>
> If a binary is returned, then the value will be parsed
> to the tuple form automatically. The value must be in
> the same format as the etag header, including quotes.
### is_authorized
> * Methods: all
> * Value type: true | {false, AuthHeader}
> * Default value: true
>
> Return whether the user is authorized to perform the action.
>
> This function should be used to perform any necessary
> authentication of the user before attempting to perform
> any action on the resource.
>
> If the authentication fails, the value returned will be sent
> as the value for the www-authenticate header in the
> `401 Unauthorized` response.
### is_conflict
> * Methods: PUT
> * Value type: boolean()
> * Default value: false
>
> Return whether the put action results in a conflict.
>
> A `409 Conflict` response will be sent if this function
> returns `true`.
### known_content_type
> * Methods: all
> * Value type: boolean()
> * Default value: true
>
> Return whether the content-type is known.
>
> This function determines if the server understands the
> content-type, regardless of its use by the resource.
### known_methods
> * Methods: all
> * Value type: [binary()]
> * Default value: [<<"GET">>, <<"HEAD">>, <<"POST">>, <<"PUT">>, <<"PATCH">>, <<"DELETE">>, <<"OPTIONS">>]
>
> Return the list of known methods.
>
> The full list of methods known by the server should be
> returned, regardless of their use in the resource.
>
> The default value lists the methods Cowboy knows and
> implement in `cowboy_rest`.
>
> Methods are case sensitive. Standard methods are always uppercase.
### languages_provided
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Value type: [binary()]
> * Skip to the next step if undefined
>
> Return the list of languages the resource provides.
>
> The list must be ordered in order of preference.
>
> If the accept-language header was not sent, the first language
> in the list will be selected. Otherwise Cowboy will select
> the most appropriate language from the list.
>
> The chosen language will be set in the `Req` object as the meta
> value `language`.
>
> While languages are case insensitive, this callback is expected
> to return them as lowercase binary.
### last_modified
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Value type: calendar:datetime()
> * Default value: undefined
>
> Return the date of last modification of the resource.
>
> This date will be used to test against the if-modified-since
> and if-unmodified-since headers, and sent as the last-modified
> header in the response of GET and HEAD requests.
### malformed_request
> * Methods: all
> * Value type: boolean()
> * Default value: false
>
> Return whether the request is malformed.
>
> Cowboy has already performed all the necessary checks
> by the time this function is called, so few resources
> are expected to implement it.
>
> The check is to be done on the request itself, not on
> the request body, which is processed later.
### moved_permanently
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Value type: {true, URL} | false
> * Default value: false
>
> Return whether the resource was permanently moved.
>
> If it was, its new URL is also returned and sent in the
> location header in the response.
### moved_temporarily
> * Methods: GET, HEAD, POST, PATCH, DELETE
> * Value type: {true, URL} | false
> * Default value: false
>
> Return whether the resource was temporarily moved.
>
> If it was, its new URL is also returned and sent in the
> location header in the response.
### multiple_choices
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Value type: boolean()
> * Default value: false
>
> Return whether there are multiple representations of the resource.
>
> This function should be used to inform the client if there
> are different representations of the resource, for example
> different content-type. If this function returns `true`,
> the response body should include information about these
> different representations using `cowboy_req:set_resp_body/2`.
> The content-type of the response should be the one previously
> negociated and that can be obtained by calling
> `cowboy_req:meta(media_type, Req)`.
### options
> * Methods: OPTIONS
> * Value type: ok
> * Default value: ok
>
> Handle a request for information.
>
> The response should inform the client the communication
> options available for this resource.
>
> By default, Cowboy will send a `200 OK` response with the
> allow header set.
### previously_existed
> * Methods: GET, HEAD, POST, PATCH, DELETE
> * Value type: boolean()
> * Default value: false
>
> Return whether the resource existed previously.
### resource_exists
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Value type: boolean()
> * Default value: true
>
> Return whether the resource exists.
>
> If it exists, conditional headers will be tested before
> attempting to perform the action. Otherwise, Cowboy will
> check if the resource previously existed first.
### service_available
> * Methods: all
> * Value type: boolean()
> * Default value: true
>
> Return whether the service is available.
>
> This function can be used to test that all relevant backend
> systems are up and able to handle requests.
>
> A `503 Service Unavailable` response will be sent if this
> function returns `false`.
### uri_too_long
> * Methods: all
> * Value type: boolean()
> * Default value: false
>
> Return whether the requested URI is too long.
>
> Cowboy has already performed all the necessary checks
> by the time this function is called, so few resources
> are expected to implement it.
>
> A `414 Request-URI Too Long` response will be sent if this
> function returns `true`.
### valid_content_headers
> * Methods: all
> * Value type: boolean()
> * Default value: true
>
> Return whether the content-* headers are valid.
>
> This also applies to the transfer-encoding header. This
> function must return `false` for any unknown content-*
> headers, or if the headers can't be understood. The
> function `cowboy_req:parse_header/2` can be used to
> quickly check the headers can be parsed.
>
> A `501 Not Implemented` response will be sent if this
> function returns `false`.
### valid_entity_length
> * Methods: all
> * Value type: boolean()
> * Default value: true
>
> Return whether the request body length is within acceptable boundaries.
>
> A `413 Request Entity Too Large` response will be sent if this
> function returns `false`.
### variances
> * Methods: GET, HEAD, POST, PUT, PATCH, DELETE
> * Value type: [binary()]
> * Default value: []
>
> Return the list of headers that affect the representation of the resource.
>
> These request headers return the same resource but with different
> parameters, like another language or a different content-type.
>
> Cowboy will automatically add the accept, accept-language and
> accept-charset headers to the list if the respective functions
> were defined in the resource.
>
> This operation is performed right before the `resource_exists/2`
> callback. All responses past that point will contain the vary
> header which holds this list.

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cowboy_router
=============
The `cowboy_router` middleware maps the requested host and
path to the handler to be used for processing the request.
It uses the dispatch rules compiled from the routes given
to the `compile/1` function for this purpose. It adds the
handler name and options to the environment as the values
`handler` and `handler_opts` respectively.
Environment input:
* dispatch = dispatch_rules()
Environment output:
* handler = module()
* handler_opts = any()
Types
-----
### bindings() = [{atom(), binary()}]
> List of bindings found during routing.
### constraints() = [IntConstraint | FunConstraint]
> Types:
> * IntConstraint = {atom(), int}
> * FunConstraint = {atom(), function, Fun}
> * Fun = fun((binary()) -> true | {true, any()} | false)
>
> List of constraints to apply to the bindings.
>
> The int constraint will convert the binding to an integer.
> The fun constraint allows writing custom code for checking
> the bindings. Returning a new value from that fun allows
> replacing the current binding with a new value.
### dispatch_rules() - opaque to the user
> Rules for dispatching request used by Cowboy.
### routes() = [{Host, Paths} | {Host, constraints(), Paths}]
> Types:
> * Host = Path = '_' | iodata()
> * Paths = [{Path, Handler, Opts} | {Path, constraints(), Handler, Opts}]
> * Handler = module()
> * Opts = any()
>
> Human readable list of routes mapping hosts and paths to handlers.
>
> The syntax for routes is defined in the user guide.
### tokens() = [binary()]
> List of host_info and path_info tokens found during routing.
Exports
-------
### compile(Routes) -> Dispatch
> Types:
> * Routes = routes()
> * Dispatch = dispatch_rules()
>
> Compile the routes for use by Cowboy.

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cowboy_spdy
===========
The `cowboy_spdy` module implements SPDY/3 as a Ranch protocol.
Types
-----
### opts() = [{env, cowboy_middleware:env()}
| {middlewares, [module()]}
| {onrequest, cowboy:onrequest_fun()}
| {onresponse, cowboy:onresponse_fun()}]
> Configuration for the SPDY protocol handler.
>
> This configuration is passed to Cowboy when starting listeners
> using the `cowboy:start_spdy/4` function.
>
> It can be updated without restarting listeners using the
> Ranch functions `ranch:get_protocol_options/1` and
> `ranch:set_protocol_options/2`.
Option descriptions
-------------------
The default value is given next to the option name.
- env ([{listener, Ref}])
- Initial middleware environment.
- middlewares ([cowboy_router, cowboy_handler])
- List of middlewares to execute for every requests.
- onrequest (undefined)
- Fun called every time a request is received.
- onresponse (undefined)
- Fun called every time a response is sent.
Exports
-------
None.

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cowboy_static
=============
The `cowboy_static` module implements file serving capabilities
by using the REST semantics provided by `cowboy_rest`.
Types
-----
### opts() = {priv_file, atom(), string() | binary()}
| {priv_file, atom(), string() | binary(), extra()}
| {file, string() | binary()}
| {file, string() | binary(), extra()}
| {priv_dir, atom(), string() | binary()}
| {priv_dir, atom(), string() | binary(), extra()}
| {dir, atom(), string() | binary()}
| {dir, atom(), string() | binary(), extra()}
> Configuration for the static handler.
>
> The handler can be configured for sending either one file or
> a directory (including its subdirectories).
>
> Extra options allow you to define how the etag should be calculated
> and how the mimetype of files should be detected. They are defined
> as follow, but do note that these types are not exported, only the
> `opts/0` type is public.
### extra() = [extra_etag() | extra_mimetypes()]
### extra_etag() = {etag, module(), function()} | {etag, false}
### extra_mimetypes() = {mimetypes, module(), function()}
| {mimetypes, binary() | {binary(), binary(), [{binary(), binary()}]}}

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cowboy_sub_protocol
===================
The `cowboy_sub_protocol` behaviour defines the interface used
by modules that implement a protocol on top of HTTP.
Types
-----
None.
Callbacks
---------
### upgrade(Req, Env, Handler, Opts)
-> {ok, Req, Env}
| {suspend, Module, Function, Args}
| {halt, Req}
| {error, StatusCode, Req}
> Types:
> * Req = cowboy_req:req()
> * Env = env()
> * Handler = module()
> * Opts = any()
> * Module = module()
> * Function = atom()
> * Args = [any()]
> * StatusCode = cowboy:http_status()
>
> Upgrade the protocol.
>
> Please refer to the `cowboy_middleware` manual for a
> description of the return values.

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cowboy_websocket
================
The `cowboy_websocket` module implements the Websocket protocol.
The callbacks for websocket handlers are defined in the manual
for the `cowboy_websocket_handler` behaviour.
Types
-----
### close_code() = 1000..4999
> Reason for closing the connection.
### frame() = close | ping | pong
| {text | binary | close | ping | pong, iodata()}
| {close, close_code(), iodata()}
> Frames that can be sent to the client.
Meta values
-----------
### websocket_compress
> Type: true | false
>
> Whether a websocket compression extension in in use.
### websocket_version
> Type: 7 | 8 | 13
>
> The version of the Websocket protocol being used.
Exports
-------
None.

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cowboy_websocket_handler
========================
The `cowboy_websocket_handler` behaviour defines the interface used
by Websocket handlers.
The `init/3` and `websocket_init/3` callbacks will always be called,
followed by zero or more calls to `websocket_handle/3` and
`websocket_info/3`. The `websocket_terminate/3` will always
be called last.
Types
-----
None.
Callbacks
---------
### init({TransportName, ProtocolName}, Req, Opts)
-> {upgrade, protocol, cowboy_websocket}
| {upgrade, protocol, cowboy_websocket, Req, Opts}
> Types:
> * TransportName = tcp | ssl | atom()
> * ProtocolName = http | atom()
> * Req = cowboy_req:req()
> * Opts = any()
>
> Upgrade the protocol to `cowboy_websocket`.
### websocket_init(TransportName, Req, Opts)
-> {ok, Req, State}
| {ok, Req, State, hibernate}
| {ok, Req, State, Timeout}
| {ok, Req, State, Timeout, hibernate}
| {shutdown, Req}
> Types:
> * TransportName = tcp | ssl | atom()
> * Req = cowboy_req:req()
> * Opts = any()
> * State = any()
> * Timeout = timeout()
>
> Initialize the state for this session.
>
> This function is called before the upgrade to Websocket occurs.
> It can be used to negotiate Websocket protocol extensions
> with the client. It will typically be used to register this process
> to an event manager or a message queue in order to receive
> the messages the handler wants to process.
>
> The connection will stay up for a duration of up to `Timeout`
> milliseconds after it last received data from the socket,
> at which point it will stop and close the connection.
> By default this value is set to `infinity`. It is recommended
> to either set this value or ensure by any other mechanism
> that the handler will be closed after a certain period of
> inactivity.
>
> The `hibernate` option will hibernate the process until it
> starts receiving either data from the Websocket connection
> or Erlang messages.
>
> The `shutdown` return value can be used to close the connection
> before upgrading to Websocket.
### websocket_handle(InFrame, Req, State)
-> {ok, Req, State}
| {ok, Req, State, hibernate}
| {reply, OutFrame | [OutFrame], Req, State}
| {reply, OutFrame | [OutFrame], Req, State, hibernate}
| {shutdown, Req, State}
> Types:
> * InFrame = {text | binary | ping | pong, binary()}
> * Req = cowboy_req:req()
> * State = any()
> * OutFrame = cowboy_websocket:frame()
>
> Handle the data received from the Websocket connection.
>
> This function will be called every time data is received
> from the Websocket connection.
>
> The `shutdown` return value can be used to close the
> connection. A close reply will also result in the connection
> being closed.
>
> The `hibernate` option will hibernate the process until
> it receives new data from the Websocket connection or an
> Erlang message.
### websocket_info(Info, Req, State)
-> {ok, Req, State}
| {ok, Req, State, hibernate}
| {reply, OutFrame | [OutFrame], Req, State}
| {reply, OutFrame | [OutFrame], Req, State, hibernate}
| {shutdown, Req, State}
> Types:
> * Info = any()
> * Req = cowboy_req:req()
> * State = any()
> * OutFrame = cowboy_websocket:frame()
>
> Handle the Erlang message received.
>
> This function will be called every time an Erlang message
> has been received. The message can be any Erlang term.
>
> The `shutdown` return value can be used to close the
> connection. A close reply will also result in the connection
> being closed.
>
> The `hibernate` option will hibernate the process until
> it receives another message or new data from the Websocket
> connection.
### websocket_terminate(Reason, Req, State) -> ok
> Types:
> * Reason = {normal, shutdown | timeout} | {remote, closed} | {remote, cowboy_websocket:close_code(), binary()} | {error, badencoding | badframe | closed | atom()}
> * Req = cowboy_req:req()
> * State = any()
>
> Perform any necessary cleanup of the state.
>
> The connection will be closed and the process stopped right
> after this call.

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Cowboy Function Reference
=========================
The function reference documents the public interface of Cowboy.
* [The Cowboy Application](cowboy_app.md)
* [cowboy](cowboy.md)
* [cowboy_handler](cowboy_handler.md)
* [cowboy_http_handler](cowboy_http_handler.md)
* [cowboy_loop_handler](cowboy_loop_handler.md)
* [cowboy_middleware](cowboy_middleware.md)
* [cowboy_protocol](cowboy_protocol.md)
* [cowboy_req](cowboy_req.md)
* [cowboy_rest](cowboy_rest.md)
* [cowboy_router](cowboy_router.md)
* [cowboy_spdy](cowboy_spdy.md)
* [cowboy_static](cowboy_static.md)
* [cowboy_sub_protocol](cowboy_sub_protocol.md)
* [cowboy_websocket](cowboy_websocket.md)
* [cowboy_websocket_handler](cowboy_websocket_handler.md)
* [HTTP status codes](http_status_codes.md)