ActiveMQ -- dead letter queue

Dead letter queue

Dead letter queue ：Dead Letter Queue

After a message is sent repeatedly many times （ Default retransmission 6 Time ,redeliveryCounter=6）, Will be moved to the dead letter queue . Developers can use this queue View error messages , To intervene artificially .

Used in general production environment mq When we design two queues ：

1. Core business queue ： Handle normal business logic

2. Dead letter queue ： Handling exception information

To configure

SharedDeadLetterStrategy： Share dead letter queue policy

Will all DeadLetter Saved in a shared queue , This is a activemq Default policy . The shared queue defaults to “ActiveMQ.DLQ”, Can pass “deadLetterQueue” Property to set .

<deadLetterStrategy>
    <sharedDeadLetterStrategy deadLetterQueue="DLQ-QUEUE" />
</deadLetterStrategy>

IndividualDeadLetterStrategy： Independent dead letter queue strategy

hold DeadLetter Put them into their respective dead letter queues .

about queue for ： The prefix of dead letter channel is... By default “ActiveMQ.DLQ.Queue”

about topic for ： The prefix of dead letter channel is... By default “ActiveMQ.DLQ.Topic”

Like queues order, Then its corresponding dead letter channel is “ActiveMQ.DLQ.Queue.Order”

We use "queuePrefix","topicPrefix" To specify the above prefix

By default ,queue and topic,broker Will use queue To preserve DeadLetter, That is, the dead letter channel is usually Queue, You can also specify Topic：

<policyEntry queue="order">
    <deadLetterStrategy>
    	<individualDeadLetterStrategy queuePrefix="DLQ." useQueueForQueueMessages="false" />
    </deadLetterStrategy>
</policyEntry>

Queue Order What happened in DeadLetter Save in DLQ.Order in , But in this case DLQ.Order by topic.

useQueueForQueueMessages： To indicate whether or not to topic Of DeadLetter Save in Queue in . Default true

Automatically delete expired messages

Sometimes you need to delete expired messages without sending them to the dead letter queue ."processExpired" Indicates whether to put expired messages in the dead letter queue , Default true

<policyEntry queue=">">
    <deadLetterStrategy>
    	<sharedDeadLetterStrategy processExpired="false" />
    </deadLetterStrategy>
</policyEntry>

Store non persistent messages to the dead letter queue

By default ,mq Will not put non persistent toxic messages in the dead letter queue .

"processNonPersistent" Indicates whether to put non persistent messages into the dead letter queue , Default false, Don't put

<!-- queue=">"  Represents all valid  -->
<policyEntry queue=">">
    <deadLetterStrategy>
    	<sharedDeadLetterStrategy processNonPersistent="true" />
    </deadLetterStrategy>
</policyEntry>