Dead letter queue

In message queueing the dead letter queue is a service implementation to store messages that meet one or more of the following criteria:

1. Message that is sent to a queue that does not exist.[1][2]
2. Queue length limit exceeded.
3. Message length limit exceeded.
4. Message is rejected by another queue exchange.[3]
5. Message reaches a threshold read counter number, because it is not consumed. Sometimes this is called a "back out queue".

Dead letter queue storing of these messages allows developers to look for common patterns and potential software problems.[4]

Queueing systems that incorporate dead letter queues include Amazon Simple Queue Service[4], Apache ActiveMQ, HornetQ, Microsoft Message Queuing[1], Microsoft Azure Event Grid and Azure Service Bus[5], WebSphere MQ[6], Rabbit MQ[3] and Apache Pulsar[7],[8]

References

1. Redkar, Arohi (2004). Pro MSMQ: Microsoft Message Queue Programming. Apress. p. 148. ISBN 1430207329.
2. "Dead-letter queues". IBM. Retrieved 23 February 2014.
3. RabbitMQ dead letter queue "Dead Letter Exchanges".
4. "Using Amazon SQS Dead Letter Queues". Amazon. Retrieved 23 February 2014.
5. spelluru. "Compare Azure messaging services". docs.microsoft.com. Retrieved 2020-01-17.
6. Böhm-Mäder, Johannes. WebSphere MQ Security: Tales of Scowling Wolves Among Unglamorous Sheep. BoD. p. 68. ISBN 3842381506.
7. "Apache Pulsar documentation".
8. "Apache Pulsar PIP-22:Dead Letter Topic".