Dead Letter Channel

Dead Letter Channel pattern is a must when working with queues and integration, and when you need to guarantee a message's delivery. In this pattern, when a message delivery fails, normally after several retries, it is moved from its queue to a special queue for an ad hoc treatment later.

You can find out more about this pattern by visiting: http://www.enterpriseintegrationpatterns.com/patterns/messaging/DeadLetterChannel.html, where we can see the following explanation diagram:

The Dead Letter Channel where the message finally ends is typically another queue that receives special treatment from administrators because all messages in this queue mean an error in the system.

WSO2 EI Message Broker implements this pattern out of the box, so we just need to set a number of retries, which, by default, is set to 10. We can modify it by following these steps:

1. Edit the $EI_HOME/wso2/broker/conf/broker.xml file.
2. Locate the maximumRedeliveryAttempts XML tag and set the desired attempts...