![]() ![]() This lets you create highly available consumers while ensuring that at any moment in time, only one of them receives messages, which until now was not possible to attain with RabbitMQ.Īn example of how to declare a queue with the Single Active Consumer feature in Elixir: Single Active Consumer enables you to attach multiple consumers to a queue, while only one of the consumers is active. This is not unique to Quorum Queues, but it’s still important to mention, that even though the Exclusive Queue feature was lost, we gain a new feature that is even better in many ways and was a frequently requested enhancement. Since all messages in Quorum Queues are persistent, the AMQP “delivery-mode” option has no effect on their operation. They also do not support, as of 3.8.2, message TTLs and message priorities 2.Īs the use case for Quorum Queues is data safety, they also cannot be declared as exclusive, which would mean they get deleted as soon as the consumer disconnects. They can not be non-durable, because the Raft log is always written to disk, so they can never be declared as transient. ![]() Quorum queues come with a few special features and restrictions. All communication is routed to the Queue Leader, which means the queue leader locality has an effect on the latency and bandwidth requirement of the messages, however the effect should be lower than it was in Classic Queues.Ĭonsuming from a Quorum Queue is done in the same fashion as other types of queues. We can see that a Quorum queue has a Leader, this roughly serves the same purpose as it did for the Classic Queue Master. :server_initiated_close, 406, "PRECONDITION_FAILED - invalid property 'non-durable' for queue 'my-quorum-queue'Īfter declaring the queue, we can observe that it is indeed a quorum type on the Management Interface: clare(publisher_chan, "my-quorum-queue", durable: true, arguments: )Īn important difference between Classic and Quorum Queues is that Quorum Queues can only be declared durable, otherwise the following error message is raised: The x-queue-type argument needs to be provided with the value quorum when creating the queue.įor example, using the Elixir AMQP client 1, declaring a Quorum Queue is as follows: Quorum queues are created differently, but should be compatible with all client applications which allow you to provide arguments when declaring a queue. ![]() In the past, replication of queues was specified by using policies in conjunction with Classic Queues. This works the very same way for Quorum Queues, whereby the leader, by default, runs on the node the client application that created it was connected to, and followers are created on the rest of the nodes in the cluster. Usage of Quorum QueuesĪ Classic Queue has a master running somewhere on a node in the cluster, while the mirrors run on other nodes. This queue type is important when RabbitMQ is used in a clustered installation, it provides less network intensive message replication using the Raft protocol underneath. The Quorum Queue is a new type of queue, which is expected to replace the default queue (which is now called classic) in the future, for some use cases. ![]() In RabbitMQ 3.8.0, one of the most significant new features was the introduction of Quorum Queues. ![]()
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