2016-08-30 14:18:14 +02:00
|
|
|
[[flow_diagram]]
|
2016-08-30 13:07:35 +02:00
|
|
|
== Flow diagram
|
|
|
|
|
|
2017-07-19 23:03:14 +02:00
|
|
|
Cowboy is a lightweight HTTP server with support for HTTP/1.1,
|
|
|
|
|
HTTP/2 and Websocket.
|
2017-01-02 14:20:15 +01:00
|
|
|
|
2017-07-19 23:03:14 +02:00
|
|
|
It is built on top of Ranch. Please see the Ranch guide for more
|
|
|
|
|
information about how the network connections are handled.
|
2017-01-02 14:20:15 +01:00
|
|
|
|
2017-07-19 23:03:14 +02:00
|
|
|
=== Overview
|
2017-01-02 14:20:15 +01:00
|
|
|
|
2017-07-19 23:03:14 +02:00
|
|
|
Placeholder section.
|
|
|
|
|
|
|
|
|
|
// @todo Make the diagram.
|
|
|
|
|
|
|
|
|
|
=== Number of processes per connection
|
|
|
|
|
|
|
|
|
|
By default, Cowboy will use one process per connection,
|
|
|
|
|
plus one process per set of request/response (called a
|
|
|
|
|
stream, internally).
|
|
|
|
|
|
|
|
|
|
The reason it creates a new process for every request is due
|
|
|
|
|
to the requirements of HTTP/2 where requests are executed
|
|
|
|
|
concurrently and independently from the connection. The
|
|
|
|
|
frames from the different requests end up interleaved on
|
|
|
|
|
the single TCP connection.
|
|
|
|
|
|
|
|
|
|
The request processes are never reused. There is therefore
|
|
|
|
|
no need to perform any cleanup after the response has been
|
|
|
|
|
sent. The process will terminate and Erlang/OTP will reclaim
|
|
|
|
|
all memory at once.
|
|
|
|
|
|
|
|
|
|
Cowboy ultimately does not require more than one process
|
|
|
|
|
per connection. It is possible to interact with the connection
|
|
|
|
|
directly from a stream handler, a low level interface to Cowboy.
|
|
|
|
|
They are executed from within the connection process, and can
|
|
|
|
|
handle the incoming requests and send responses. This is however
|
|
|
|
|
not recommended in normal circumstances, as a stream handler
|
|
|
|
|
taking too long to execute could have a negative impact on
|
|
|
|
|
concurrent requests or the state of the connection itself.
|
|
|
|
|
|
|
|
|
|
=== Date header
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
=== Binaries
|
|
|
|
|
|
|
|
|
|
Cowboy makes extensive use of 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.
|
|
|
|
|
|
|
|
|
|
Binaries may end up being shared between processes. This
|
|
|
|
|
can lead to some large memory usage when one process keeps
|
|
|
|
|
the binary data around forever without freeing it. If you
|
|
|
|
|
see some weird memory usage in your application, this might
|
|
|
|
|
be the cause.
|
