Dead Letter Channel Enterprise Application Integration Pattern
Idea of having a dead letter channel is to handle Message failures. Message failures can be occurred due to several reasons.
Transport level failures
Due to bad Configuration
Problem with Message Consumer end
In a failure Message will be routed to the dead letter channel. So that it can act as a Message archive mechanism , Re router or a special channel to process the bad messages.
Having a Message archive system will be useful since later a Dead message can be viewed and re-delivered to the intended end point manually by a admin console.This will be useful to identify the Configuration problems
Message Re-delivery is also a major part of a dead letter channel implementation. If we take a normal scenario like simple DB quarries or web-service calls some times a message will fail because of the endpoint have a higher load or some other temporary issues with the endpoint . So simply re -delivering the message after a certain time interval will cause message to be delivered successfully.
Apache Synapse is a Open source esb and a message Mediation framework that support several Enterprise application integration patterns. For this summer(2010) Google Summer of code program I applied for the proposal of Implementing A Dead Letter Channel for Apache synapse. This is the link to my proposal .