Dead letter queue explained

In message queueing a dead letter queue (DLQ) is a service implementation to store messages that the messaging system cannot or should not deliver.[1] Although implementation-specific, messages can be routed to the DLQ for the following reasons:

  1. The message is sent to a queue that does not exist.[2] [3]
  2. The maximum queue length is exceeded.
  3. The message exceeds the size limit.
  4. The message expires because it reached the TTL (time to live)[4]
  5. The message is rejected by another queue exchange.[5]
  6. The message has been read and rejected too many times.[6]

Routing these messages to a dead letter queue enables analysis of common fault patterns and potential software problems. If a message consumer receives a message that it considers invalid, it can instead forward it an Invalid Message Channel,[7] allowing a separation between application-level faults and delivery failures.

Queueing systems that incorporate dead letter queues include Amazon EventBridge,[8] Amazon Simple Queue Service,[9] Apache ActiveMQ, Google Cloud Pub/Sub,[10] HornetQ, Microsoft Message Queuing,[2] Microsoft Azure Event Grid and Azure Service Bus,[11] WebSphere MQ,[12] Solace PubSub+,[13] Rabbit MQ,[5] Confluent Cloud[14] and Apache Pulsar.[15] [16]

See also

Notes and References

  1. Web site: Dead Letter Channel. www.enterpriseintegrationpatterns.com.
  2. Book: Redkar, Arohi. Pro MSMQ: Microsoft Message Queue Programming. Apress. 2004. 1430207329. 148.
  3. Web site: Dead-letter queues. IBM. 23 February 2014.
  4. Web site: Dead Letter Exchanges — RabbitMQ. 2020-12-06. www.rabbitmq.com.
  5. RabbitMQ dead letter queue Web site: Dead Letter Exchanges.
  6. Web site: Amazon SQS dead-letter queues. AWS.
  7. Web site: Invalid Message Channel. www.enterpriseintegrationpatterns.com.
  8. Web site: Amazon EventBridge announces support for Dead Letter Queues . Amazon.
  9. Web site: Using Amazon SQS Dead Letter Queues. Amazon. 23 February 2014.
  10. Web site: Forwarding to dead-letter topics Cloud Pub/Sub. 2020-12-26. Google Cloud. en.
  11. Web site: Compare Azure messaging services. spelluru. docs.microsoft.com. en-us. 2020-01-17.
  12. Book: Böhm-Mäder, Johannes. WebSphere MQ Security: Tales of Scowling Wolves Among Unglamorous Sheep. 14 December 2011 . BoD. 68. 978-3842381506.
  13. Web site: Solace Dead Message Queues.
  14. Web site: Confluent Cloud documentation.
  15. Web site: Apache Pulsar documentation.
  16. Web site: Apache Pulsar PIP-22:Dead Letter Topic. .

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