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5e006be01f
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.
22 lines
574 B
Erlang
22 lines
574 B
Erlang
%% Feel free to use, reuse and abuse the code in this file.
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-module(http_handler_long_polling).
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-behaviour(cowboy_http_handler).
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-export([init/3, handle/2, info/3, terminate/2]).
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init({_Transport, http}, Req, _Opts) ->
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erlang:send_after(500, self(), timeout),
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{loop, Req, 9, 5000, hibernate}.
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handle(_Req, _State) ->
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exit(badarg).
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info(timeout, Req, 0) ->
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{ok, Req2} = cowboy_http_req:reply(102, [], [], Req),
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{ok, Req2, 0};
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info(timeout, Req, State) ->
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erlang:send_after(500, self(), timeout),
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{loop, Req, State - 1, hibernate}.
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terminate(_Req, _State) ->
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ok.
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