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basic.consume指的是channel在 某个队列上注册消费者,那在这个队列有消息来了之后,就会把消息转发到给此channel处理,如果 这个队列有多个消费者,则会采用轮转的方式将消息分发给消息者.
首先是rabbit_reader接收数据包后,解析组装出其中的method,channel方法交给channel处理.具体过程见http://www.cnblogs.com/haoqingchuan/p/4354692.html
channel进程处理basic.consume的方法.先从状态中查看是否已经存在此tag(以channel为域,不同的consumer_tag标识了不同的消费者,每个channel的内的consumer tag必须是唯一的).如果没有查找到则正常,如果未对队列名字命名,则会产生一个uuid来作为队列名.
1 handle_method(#‘basic.consume‘{queue = QueueNameBin, 2 consumer_tag = ConsumerTag, 3 no_local = _, % FIXME: implement 4 no_ack = NoAck, 5 exclusive = ExclusiveConsume, 6 nowait = NoWait, 7 arguments = Args}, 8 _, State = #ch{consumer_prefetch = ConsumerPrefetch, 9 consumer_mapping = ConsumerMapping}) -> 10 case dict:find(ConsumerTag, ConsumerMapping) of 11 error -> 12 QueueName = qbin_to_resource(QueueNameBin, State), 13 check_read_permitted(QueueName, State), 14 ActualConsumerTag = 15 case ConsumerTag of 16 <<>> -> rabbit_guid:binary(rabbit_guid:gen_secure(), 17 "amq.ctag"); 18 Other -> Other 19 end, 20 case basic_consume( 21 QueueName, NoAck, ConsumerPrefetch, ActualConsumerTag, 22 ExclusiveConsume, Args, NoWait, State) of 23 {ok, State1} -> 24 {noreply, State1}; 25 {error, exclusive_consume_unavailable} -> 26 rabbit_misc:protocol_error( 27 access_refused, "~s in exclusive use", 28 [rabbit_misc:rs(QueueName)]) 29 end; 30 {ok, _} -> 31 %% Attempted reuse of consumer tag. 32 rabbit_misc:protocol_error( 33 not_allowed, "attempt to reuse consumer tag ‘~s‘", [ConsumerTag]) 34 end;
1 basic_consume(QueueName, NoAck, ConsumerPrefetch, ActualConsumerTag, 2 ExclusiveConsume, Args, NoWait, 3 State = #ch{conn_pid = ConnPid, 4 limiter = Limiter, 5 consumer_mapping = ConsumerMapping}) -> 6 case rabbit_amqqueue:with_exclusive_access_or_die( 7 QueueName, ConnPid, 8 fun (Q) -> 9 {rabbit_amqqueue:basic_consume( 10 Q, NoAck, self(), 11 rabbit_limiter:pid(Limiter), 12 rabbit_limiter:is_active(Limiter), 13 ConsumerPrefetch, ActualConsumerTag, 14 ExclusiveConsume, Args, 15 ok_msg(NoWait, #‘basic.consume_ok‘{ 16 consumer_tag = ActualConsumerTag})), 17 Q} 18 end) of 19 {ok, Q = #amqqueue{pid = QPid, name = QName}} -> 20 CM1 = dict:store( 21 ActualConsumerTag, 22 {Q, {NoAck, ConsumerPrefetch, ExclusiveConsume, Args}}, 23 ConsumerMapping), 24 State1 = monitor_delivering_queue( 25 NoAck, QPid, QName, 26 State#ch{consumer_mapping = CM1}), 27 {ok, case NoWait of 28 true -> consumer_monitor(ActualConsumerTag, State1); 29 false -> State1 30 end}; 31 {{error, exclusive_consume_unavailable} = E, _Q} -> 32 E 33 end.
rabbit_amqqueue.erl
1 basic_consume(#amqqueue{pid = QPid, name = QName}, NoAck, ChPid, LimiterPid, 2 LimiterActive, ConsumerPrefetchCount, ConsumerTag, 3 ExclusiveConsume, Args, OkMsg) -> 4 ok = check_consume_arguments(QName, Args), 5 delegate:call(QPid, {basic_consume, NoAck, ChPid, LimiterPid, LimiterActive, 6 ConsumerPrefetchCount, ConsumerTag, ExclusiveConsume, 7 Args, OkMsg}).
rabbit_amqqueue_process
1 handle_call({basic_consume, NoAck, ChPid, LimiterPid, LimiterActive, 2 PrefetchCount, ConsumerTag, ExclusiveConsume, Args, OkMsg}, 3 _From, State = #q{consumers = Consumers, 4 exclusive_consumer = Holder}) -> 5 case check_exclusive_access(Holder, ExclusiveConsume, State) of 6 in_use -> reply({error, exclusive_consume_unavailable}, State); 7 ok -> Consumers1 = rabbit_queue_consumers:add( 8 ChPid, ConsumerTag, NoAck, 9 LimiterPid, LimiterActive, 10 PrefetchCount, Args, is_empty(State), 11 Consumers), 12 ExclusiveConsumer = 13 if ExclusiveConsume -> {ChPid, ConsumerTag}; 14 true -> Holder 15 end, 16 State1 = State#q{consumers = Consumers1, 17 has_had_consumers = true, 18 exclusive_consumer = ExclusiveConsumer}, 19 ok = maybe_send_reply(ChPid, OkMsg), 20 emit_consumer_created(ChPid, ConsumerTag, ExclusiveConsume, 21 not NoAck, qname(State1), 22 PrefetchCount, Args, none), 23 notify_decorators(State1), 24 reply(ok, run_message_queue(State1)) 25 end;
rabbit_queue_consumers.erl
更新进程字典,并为队列增加新消费者.
1 add(ChPid, CTag, NoAck, LimiterPid, LimiterActive, Prefetch, Args, IsEmpty, 2 State = #state{consumers = Consumers, 3 use = CUInfo}) -> 4 C = #cr{consumer_count = Count, 5 limiter = Limiter} = ch_record(ChPid, LimiterPid), 6 Limiter1 = case LimiterActive of 7 true -> rabbit_limiter:activate(Limiter); 8 false -> Limiter 9 end, 10 C1 = C#cr{consumer_count = Count + 1, limiter = Limiter1}, 11 update_ch_record( 12 case parse_credit_args(Prefetch, Args) of 13 {0, auto} -> C1; 14 {_Credit, auto} when NoAck -> C1; 15 {Credit, Mode} -> credit_and_drain( 16 C1, CTag, Credit, Mode, IsEmpty) 17 end), 18 Consumer = #consumer{tag = CTag, 19 ack_required = not NoAck, 20 prefetch = Prefetch, 21 args = Args}, 22 State#state{consumers = add_consumer({ChPid, Consumer}, Consumers), 23 use = update_use(CUInfo, active)}.
%%将consumer加入consumers列表里面,也就是后面分发消息的时候会从这个列表里将消息取出
1 in(X, 0, { queue, [_] = In, [], 1}) -> 2 {queue, [X], In, 2}; 3 in(X, 0, {queue, In, Out, Len}) when is_list(In), is_list(Out) -> 4 {queue, [X|In], Out, Len + 1};
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原文地址：http://www.cnblogs.com/haoqingchuan/p/4550794.html
