Dead Letter Queue Max Size and behavior when reach the throttling thresholds?

Question

I'm needing to gather more technical info regarding the dead-letter queue, unfortunatelly I can not find online things like its maximum size or what is the behavior when it reach the max allowed quota (whatever it is)? messages got lost? where will they go?

Answer 1

Hi Jorge Ramirez Duran Thanks for reaching out. There is no separate size limit for the dead letter queue. The overall size value for the queue or topic applies. So, the size is calculated bases on sum of active, scheduled, deferred and deadlettered messages.

If the dead-letter queue is full and a message cannot be delivered to any receiver, or if a message couldn't be processed and is moved to the dead-letter queue, the message will not be lost rather the incoming messages will be throttled. It's important to monitor the size of the dead-letter queue and take corrective action if it approaches its maximum size.

To avoid such conditions, you can configure Service Bus to automatically forward dead-lettered messages to another queue. This can be useful for implementing a retry mechanism or for further processing of dead-lettered messages usinghttps://docs.microsoft.com/en-us/dotnet/api/microsoft.azure.servicebus.management.queuedescription.forwarddeadletteredmessagesto?view=azure-dotnet#Microsoft_Azure_ServiceBus_Management_QueueDescription_ForwardDeadLetteredMessagesTo

You can also use Azure Monitor to monitor the size of the dead-letter queue and set up alerts to notify you when the queue reaches a certain size. This can help you take proactive measures to prevent the queue from reaching its maximum size and losing messages.

https://learn.microsoft.com/en-us/azure/service-bus-messaging/monitor-service-bus-reference#message-metrics

I hope this information helps. Let me know if you have any other questions.

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