AMQP/RabbitMQ-按顺序处理消息 [英] AMQP/RabbitMQ - Process messages sequentially

问题描述

我有一个直接交流中心.还有一个队列，绑定到此交换.

该队列有两个使用者.使用者完成相应的处理后，便会手动确认消息.

消息在逻辑上是按顺序排列/排序的，应按该顺序进行处理.是否可以强制要求在消费者A和消费者B之间依次接收和处理所有消息?换句话说，请防止A和B同时处理邮件.

注意:消费者不共享相同的连接和/或渠道.这意味着我不能使用<channel>.basicQoS(1);.

这个问题的理论依据:两个消费者都是相同的.如果其中一个发生故障，则另一个队列开始处理消息，并且一切正常，而无需任何干预.

解决方案

通常，MQ系统的重点是分配工作负载.当然，在某些情况下，消息N的处理取决于消息N-1或N-1消息本身的处理结果.

如果A和B无法同时处理消息，那么为什么不只有A或只有B?正如我所看到的，拥有2个消费者不会使您节省任何钱，因为一个消费者只有在另一个消费者无法工作时才可以工作...

在您的情况下，最好只有一个使用者，但实际上要在处理部分进行并行化(实际上不是一个字).

只需补充说，RMQ不管任何条件如何都将消息均匀地分发给所有使用者(以循环方式).当然，这是预取设置为1时的默认值. 此处的更多信息，寻找公平派送". >

I have one direct exchange. There is also one queue, bound to this exchange.

I have two consumers for that queue. The consumers are manually ack'ing the messages once they've done the corresponding processing.

The messages are logically ordered/sorted, and should be processed in that order. Is it possible to enforce that all messages are received and processed sequentially accross consumer A and consumer B? In other words, prevent A and B from processing messages at the same time.

Note: the consumers are not sharing the same connection and/or channel. This means I cannot use <channel>.basicQoS(1);.

Rationale of this question: both consumers are identicall. If one goes down, the other queue starts processing messages and everything keeps working without any required intervention.

解决方案

Usually the point of a MQ system is to distribute workload. Of course, there are some situations where processing of message N depends on result of processing the message N-1, or even the N-1 message itself.

If A and B can't process messages at the same time, then why not just have A or just B? As I see it, you are not saving anything with having 2 consumers in a way that one can work only when the other one is not...

In your case, it would be best to have one consumer but to actually do the parallelisation (not a word really) on the processing part.

Just to add that RMQ is distributing messages evenly to all consumers (in round-robin fashion) regardless on any criteria. Of course this is when prefetch is set to 1, which by default it is. More info on that here, look for "fair dispatch".

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