diff options
| -rw-r--r-- | src/rabbit_writer.erl | 42 |
1 files changed, 39 insertions, 3 deletions
diff --git a/src/rabbit_writer.erl b/src/rabbit_writer.erl index 7cba7170a4..897d937443 100644 --- a/src/rabbit_writer.erl +++ b/src/rabbit_writer.erl @@ -15,6 +15,24 @@ %% -module(rabbit_writer). + +%% This module backs writer processes ("writers"). The responsibility of +%% a writer is to serialise protocol methods and write them to the socket. +%% Every writer is associated with a channel and normally it's the channel +%% that delegates method delivery to it. However, rabbit_reader +%% (connection process) can use this module's functions to send data +%% on channel 0, which is only used for connection negotiation and +%% other "special" purposes. +%% +%% This module provides multiple functions that send protocol commands, +%% including some that are credit flow-aware. +%% +%% Writers perform internal buffering. When the amount of data +%% buffered exceeds a threshold, a socket flush is performed. +%% See FLUSH_THRESHOLD for details. +%% +%% When a socket write fails, writer will exit. + -include("rabbit.hrl"). -include("rabbit_framing.hrl"). @@ -32,8 +50,23 @@ %% internal -export([enter_mainloop/2, mainloop/2, mainloop1/2]). --record(wstate, {sock, channel, frame_max, protocol, reader, - stats_timer, pending}). +-record(wstate, { + %% socket (port) + sock, + %% channel number + channel, + %% connection-negotiated frame_max setting + frame_max, + %% see #connection.protocol in rabbit_reader + protocol, + %% connection (rabbit_reader) process + reader, + %% statistics emission timer + stats_timer, + %% data pending delivery (between socket + %% flushes) + pending +}). -define(HIBERNATE_AFTER, 5000). @@ -311,8 +344,11 @@ internal_send_command_async(MethodRecord, Content, rabbit_basic:maybe_gc_large_msg(Content), maybe_flush(State#wstate{pending = [Frames | Pending]}). +%% When the amount of protocol method data buffered exceeds +%% this threshold, a socket flush is performed. +%% %% This magic number is the tcp-over-ethernet MSS (1460) minus the -%% minimum size of a AMQP basic.deliver method frame (24) plus basic +%% minimum size of a AMQP 0-9-1 basic.deliver method frame (24) plus basic %% content header (22). The idea is that we want to flush just before %% exceeding the MSS. -define(FLUSH_THRESHOLD, 1414). |