the dlq-badmail queue (Dead letter queue) is used to hold messages that have failed or expired processing.

The message is redelivered (re-sent) when the following occurs: A transacted session is used and rollback () is called (using a transaction session, and the rollback () method is called). A transacted session is closed before commits is called (a transaction session, the commit was called before closing). A session is the using Client_acknowledge and Session.recover () is called (using the Client_acknowledge sign mode in the session, and called the Session.recover () method).

When a message is redelivered over Maximumredeliveries (the default is 6 times, refer to the following link), the broker is sent a "Poison ack", which is considered a Poison pill (poison pill), The broker will then send this message to DLQ for subsequent processing.

The default dead-letter queue is ACTIVEMQ.DLQ, and if not specifically specified, the Badmail is sent to this queue.

The default persistent message expires and is sent to DLQ, and non-persistent messages are not sent to DLQ

You can adjust the dead-letter send policy through the configuration file (Activemq.xml).

1. Do not use the default dead-letter queue

The default dead-letter messages for all queues are sent to the same default dead-letter queue, which is not easy to administer. Modifications can be made by individualdeadletterstrategy or shareddeadletterstrategy policies. As follows: