From 5e006be01fb9af2cbb6b62bec695a2c160733cf4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= Date: Mon, 10 Oct 2011 17:27:52 +0200 Subject: Add support for loops in standard HTTP handlers Now init/3 can return one of the following values to enable loops: - {loop, Req, State} - {loop, Req, State, hibernate} - {loop, Req, State, Timeout} - {loop, Req, State, Timeout, hibernate} Returning one of these tuples will activate looping in the HTTP handler. When looping, handle/2 is never called. Instead, Cowboy will listen for Erlang messages and forward them to the info/3 function of the handler. If a timeout is defined, Cowboy will also close the connection when no message has been received for Timeout milliseconds. The info/3 function is defined as info(Msg, Req, State). It can return either of the following tuples: - {ok, Req, State} - {loop, Req, State} - {loop, Req, State, hibernate} The first one ends the connection, calling terminate/2 before closing. The others continue the loop. Loops are useful when writing long-polling handlers that need to wait and don't expect to receive anything. Therefore it is recommended to set a timeout to close the connection if nothing arrives after a while and to enable hibernate everywhere. Normal HTTP handlers shouldn't need to use this and as such info/3 was made optional. --- test/http_handler_long_polling.erl | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 test/http_handler_long_polling.erl (limited to 'test/http_handler_long_polling.erl') diff --git a/test/http_handler_long_polling.erl b/test/http_handler_long_polling.erl new file mode 100644 index 0000000..374e244 --- /dev/null +++ b/test/http_handler_long_polling.erl @@ -0,0 +1,22 @@ +%% Feel free to use, reuse and abuse the code in this file. + +-module(http_handler_long_polling). +-behaviour(cowboy_http_handler). +-export([init/3, handle/2, info/3, terminate/2]). + +init({_Transport, http}, Req, _Opts) -> + erlang:send_after(500, self(), timeout), + {loop, Req, 9, 5000, hibernate}. + +handle(_Req, _State) -> + exit(badarg). + +info(timeout, Req, 0) -> + {ok, Req2} = cowboy_http_req:reply(102, [], [], Req), + {ok, Req2, 0}; +info(timeout, Req, State) -> + erlang:send_after(500, self(), timeout), + {loop, Req, State - 1, hibernate}. + +terminate(_Req, _State) -> + ok. -- cgit v1.2.3