Suppose I have an application fed by a MQ queue. When the application receives a message that contains errors, the application itself pushes the received message to a certain invalid message queue.
My question is: what is the recommended way to have the receiving application append the failure/rejection reason to the message pushed on the invalid message queue? Some solutions come to mind, but I'm unsure which one is considered "best-practice":
If all that you need is to place a reason code in the message, use the MQMD.Feedback field with one of the standard reason codes. In WMQ v7.0 or later, the application can set any number of message properties which are then readable both with JMS semantics and native WMQ API calls. It is up to you to define the taxonomy for naming the application-defined properties.
If the message is requeued to the Dead Letter Queue instead of an application-owned backout queue, it is customary to prepend a Dead Letter Header to it. The MQDLH structure contains a field for the reason code describing why that the message was requeued. As a rule, applications should avoid using the DLQ in favor of an application-owned queue. When applications do use the DLQ, it is normal that they should have access to put messages there but not to retrieve messages from that queue. This is because it is a system-wide resource and messages from different applications may land there. Normally, an admin application or person with elevated access is responsible for adjudicating and disposing of messages on the system DLQ.