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Implement backpressure on cowboy_req:stream_body

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This should limit the amount of memory that Cowboy is using
when a handler is sending data much faster than the network.

The new max_stream_buffer_size is a soft limit and only has
an effect when the cowboy_stream_h handler is used.
This commit is contained in:
Loïc Hoguin 2019-09-13 14:20:04 +02:00
parent 4427108b69
commit 49af57d546
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GPG key ID: 8A9DF795F6FED764
6 changed files with 91 additions and 25 deletions
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33
src/cowboy_req.erl
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@ -826,34 +826,31 @@ stream_body(_, _, #{method := <<"HEAD">>, has_sent_resp := headers}) ->
%% is converted to a data tuple, however.
stream_body({sendfile, _, 0, _}, nofin, _) ->
ok;
stream_body({sendfile, _, 0, _}, IsFin=fin,
#{pid := Pid, streamid := StreamID, has_sent_resp := headers}) ->
Pid ! {{Pid, StreamID}, {data, IsFin, <<>>}},
ok;
stream_body({sendfile, O, B, P}, IsFin,
#{pid := Pid, streamid := StreamID, has_sent_resp := headers})
stream_body({sendfile, _, 0, _}, IsFin=fin, Req=#{has_sent_resp := headers}) ->
stream_body({data, IsFin, <<>>}, Req);
stream_body({sendfile, O, B, P}, IsFin, Req=#{has_sent_resp := headers})
when is_integer(O), O >= 0, is_integer(B), B > 0 ->
Pid ! {{Pid, StreamID}, {data, IsFin, {sendfile, O, B, P}}},
ok;
stream_body(Data, IsFin=nofin, #{pid := Pid, streamid := StreamID, has_sent_resp := headers})
stream_body({data, IsFin, {sendfile, O, B, P}}, Req);
stream_body(Data, IsFin=nofin, Req=#{has_sent_resp := headers})
when not is_tuple(Data) ->
case iolist_size(Data) of
0 -> ok;
_ ->
Pid ! {{Pid, StreamID}, {data, IsFin, Data}},
ok
_ -> stream_body({data, IsFin, Data}, Req)
end;
stream_body(Data, IsFin, #{pid := Pid, streamid := StreamID, has_sent_resp := headers})
stream_body(Data, IsFin, Req=#{has_sent_resp := headers})
when not is_tuple(Data) ->
Pid ! {{Pid, StreamID}, {data, IsFin, Data}},
ok.
stream_body({data, IsFin, Data}, Req).
%% @todo Do we need a timeout?
stream_body(Msg, #{pid := Pid, streamid := StreamID}) ->
Pid ! {{Pid, StreamID}, Msg},
receive {data_ack, Pid} -> ok end.
-spec stream_events(cow_sse:event() | [cow_sse:event()], fin | nofin, req()) -> ok.
stream_events(Event, IsFin, Req) when is_map(Event) ->
stream_events([Event], IsFin, Req);
stream_events(Events, IsFin, #{pid := Pid, streamid := StreamID, has_sent_resp := headers}) ->
Pid ! {{Pid, StreamID}, {data, IsFin, cow_sse:events(Events)}},
ok.
stream_events(Events, IsFin, Req=#{has_sent_resp := headers}) ->
stream_body({data, IsFin, cow_sse:events(Events)}, Req).
-spec stream_trailers(cowboy:http_headers(), req()) -> ok.
stream_trailers(Trailers, #{pid := Pid, streamid := StreamID, has_sent_resp := headers}) ->