From db0d6f8d254f2cc01bd458dc41969e0b96991cc3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= <essen@ninenines.eu>
Date: Wed, 4 Dec 2019 11:17:34 +0100
Subject: Use active,N

This reduces the number of times we need to ask for more packets,
and as a result we get a fairly large boost in performance,
especially with HTTP/1.1.

Unfortunately this makes Cowboy require at least Erlang/OTP 21.3+
because the ssl application did not have active,N. For simplicity
the version required will be Erlang/OTP 22+.

In addition this change improves hibernate handling in
cowboy_websocket. Hibernate will now work for HTTP/2 transport
as well, and stray or unrelated messages will no longer cancel
hibernate (the process will handle the message and go back into
hibernation).

Thanks go to Stressgrid for benchmarking an early version of this
commit: https://stressgrid.com/blog/cowboy_performance_part_2/
---
 doc/src/manual/cowboy_http.asciidoc | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'doc/src/manual/cowboy_http.asciidoc')

diff --git a/doc/src/manual/cowboy_http.asciidoc b/doc/src/manual/cowboy_http.asciidoc
index 8d89ea2..b088797 100644
--- a/doc/src/manual/cowboy_http.asciidoc
+++ b/doc/src/manual/cowboy_http.asciidoc
@@ -17,6 +17,7 @@ as a Ranch protocol.
 [source,erlang]
 ----
 opts() :: #{
+    active_n                 => pos_integer(),
     chunked                  => boolean(),
     connection_type          => worker | supervisor,
     http10_keepalive         => boolean(),
@@ -51,6 +52,14 @@ Ranch functions `ranch:get_protocol_options/1` and
 
 The default value is given next to the option name:
 
+active_n (100)::
+
+The number of packets Cowboy will request from the socket at once.
+This can be used to tweak the performance of the server. Higher
+values reduce the number of times Cowboy need to request more
+packets from the port driver at the expense of potentially
+higher memory being used.
+
 chunked (true)::
 
 Whether chunked transfer-encoding is enabled for HTTP/1.1 connections.
@@ -151,6 +160,7 @@ Ordered list of stream handlers that will handle all stream events.
 
 == Changelog
 
+* *2.8*: The `active_n` option was added.
 * *2.7*: The `initial_stream_flow_size` and `logger` options were added.
 * *2.6*: The `chunked`, `http10_keepalive`, `proxy_header` and `sendfile` options were added.
 * *2.5*: The `linger_timeout` option was added.
-- 
cgit v1.2.3

