mirror of
https://github.com/ninenines/cowboy.git
synced 2025-07-15 04:30:25 +00:00
79 lines
2.9 KiB
Markdown
79 lines
2.9 KiB
Markdown
Internals
|
|
=========
|
|
|
|
Architecture
|
|
------------
|
|
|
|
Cowboy is a lightweight HTTP server.
|
|
|
|
It is built on top of Ranch. Please see the Ranch guide for more
|
|
informations.
|
|
|
|
It uses only one process per connection. The process where your
|
|
code runs is the process controlling the socket. Using one process
|
|
instead of two allows for lower memory usage.
|
|
|
|
It uses binaries. Binaries are more efficient than lists for
|
|
representing strings because they take less memory space. Processing
|
|
performance can vary depending on the operation. Binaries are known
|
|
for generally getting a great boost if the code is compiled natively.
|
|
Please see the HiPE documentation for more details.
|
|
|
|
Because querying for the current date and time can be expensive,
|
|
Cowboy generates one `Date` header value every second, shares it
|
|
to all other processes, which then simply copy it in the response.
|
|
This allows compliance with HTTP/1.1 with no actual performance loss.
|
|
|
|
One process for many requests
|
|
-----------------------------
|
|
|
|
As previously mentioned, Cowboy only use one process per connection.
|
|
Because there can be more than one request per connection with the
|
|
keepalive feature of HTTP/1.1, that means the same process will be
|
|
used to handle many requests.
|
|
|
|
Because of this, you are expected to make sure your process cleans
|
|
up before terminating the handling of the current request. This may
|
|
include cleaning up the process dictionary, timers, monitoring and
|
|
more.
|
|
|
|
Lowercase header names
|
|
----------------------
|
|
|
|
For consistency reasons it has been chosen to convert all header names
|
|
to lowercase binary strings. This prevents the programmer from making
|
|
case mistakes, and is possible because header names are case insensitive.
|
|
|
|
This works fine for the large majority of clients. However, some badly
|
|
implemented clients, especially ones found in corporate code or closed
|
|
source products, may not handle header names in a case insensitive manner.
|
|
This means that when Cowboy returns lowercase header names, these clients
|
|
will not find the headers they are looking for.
|
|
|
|
A simple way to solve this is to create an `onresponse` hook that will
|
|
format the header names with the expected case.
|
|
|
|
``` erlang
|
|
capitalize_hook(Status, Headers, Body, Req) ->
|
|
Headers2 = [{cowboy_bstr:capitalize_token(N), V}
|
|
|| {N, V} <- Headers],
|
|
{ok, Req2} = cowboy_req:reply(Status, Headers2, Body, Req),
|
|
Req2.
|
|
```
|
|
|
|
Improving performance
|
|
---------------------
|
|
|
|
By default the maximum number of active connections is set to a
|
|
generally accepted big enough number. This is meant to prevent having
|
|
too many processes performing potentially heavy work and slowing
|
|
everything else down, or taking up all the memory.
|
|
|
|
Disabling this feature, by setting the `{max_connections, infinity}`
|
|
protocol option, would give you greater performance when you are
|
|
only processing short-lived requests.
|
|
|
|
Another option is to define platform-specific socket options that
|
|
are known to improve their efficiency.
|
|
|
|
Please see the Ranch guide for more information.
|