From e4cab480dc2562378d9d046069bce2e5ab90dabd Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= Date: Wed, 19 Jul 2017 23:03:14 +0200 Subject: Remove the old architecture chapter --- doc/src/guide/flow_diagram.asciidoc | 64 +++++++++++++++++++++++++++++++++---- 1 file changed, 58 insertions(+), 6 deletions(-) (limited to 'doc/src/guide/flow_diagram.asciidoc') diff --git a/doc/src/guide/flow_diagram.asciidoc b/doc/src/guide/flow_diagram.asciidoc index ad2110d..4cb3bda 100644 --- a/doc/src/guide/flow_diagram.asciidoc +++ b/doc/src/guide/flow_diagram.asciidoc @@ -1,12 +1,64 @@ [[flow_diagram]] == Flow diagram -Placeholder chapter. +Cowboy is a lightweight HTTP server with support for HTTP/1.1, +HTTP/2 and Websocket. -Cowboy 2.0 has changed the request flow and general architecture. -You can read about the Cowboy 1.0 architecture and flow here: +It is built on top of Ranch. Please see the Ranch guide for more +information about how the network connections are handled. -* xref:architecture[Architecture] -* xref:overview[Overview] +=== Overview -This chapter will be updated in a future pre-release. +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. -- cgit v1.2.3