From a45813c60f0f983a24ea29d491b37f0590fdd087 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= <essen@ninenines.eu>
Date: Sat, 18 Feb 2017 18:26:20 +0100
Subject: Allow passing options to sub protocols

Before this commit we had an issue where configuring a
Websocket connection was simply not possible without
doing magic, adding callbacks or extra return values.
The init/2 function only allowed setting hibernate
and timeout options.

After this commit, when switching to a different
type of handler you can either return

  {module, Req, State}

or

  {module, Req, State, Opts}

where Opts is any value (as far as the sub protocol
interface is concerned) and is ultimately checked
by the custom handlers.

A large protocol like Websocket would accept only
a map there, with many different options, while a
small interface like loop handlers would allow
passing hibernate and nothing else.

For Websocket, hibernate must be set from the
websocket_init/1 callback, because init/2 executes
in a separate process.

Sub protocols now have two callbacks: one with the
Opts value, one without.

The loop handler code was largely reworked and
simplified. It does not need to manage a timeout
or read from the socket anymore, it's the job of
the protocol code. A lot of unnecessary stuff was
therefore removed.

Websocket compression must now be enabled from
the handler options instead of per listener. This
means that a project can have two separate Websocket
handlers with different options. Compression is
still disabled by default, and the idle_timeout
value was changed from inifnity to 60000 (60 seconds),
as that's safer and is also a good value for mobile
devices.
---
 doc/src/guide/ws_handlers.asciidoc | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

(limited to 'doc/src/guide/ws_handlers.asciidoc')

diff --git a/doc/src/guide/ws_handlers.asciidoc b/doc/src/guide/ws_handlers.asciidoc
index 011aa31..2c38b87 100644
--- a/doc/src/guide/ws_handlers.asciidoc
+++ b/doc/src/guide/ws_handlers.asciidoc
@@ -60,13 +60,13 @@ be:
 init(Req, State) ->
     case cowboy_req:parse_header(<<"sec-websocket-protocol">>, Req) of
         undefined ->
-            {ok, Req, State};
+            {cowboy_websocket, Req, State};
         Subprotocols ->
             case lists:keymember(<<"mqtt">>, 1, Subprotocols) of
                 true ->
                     Req2 = cowboy_req:set_resp_header(<<"sec-websocket-protocol">>,
                         <<"mqtt">>, Req),
-                    {ok, Req2, State};
+                    {cowboy_websocket, Req2, State};
                 false ->
                     {stop, Req, State}
             end
@@ -210,12 +210,13 @@ than needed.
 
 The `init/2` callback can set the timeout to be used
 for the connection. For example, this would make Cowboy
-close connections idle for more than 60 seconds:
+close connections idle for more than 30 seconds:
 
 [source,erlang]
 ----
 init(Req, State) ->
-    {cowboy_websocket, Req, State, 60000}.
+    {cowboy_websocket, Req, State, #{
+        idle_timeout => 30000}}.
 ----
 
 This value cannot be changed once it is set. It defaults to
-- 
cgit v1.2.3

