Dead-letter metric returns unexpected values

Question

In the metric dashboard for our Azure Service Bus queue there has been an unexpected behavior.

We can see in the graph that spontaneously and in a very short period of time (1-2min) the items in the dead-letter have decreased and increased. This behavior affects our alert management, as it gives us false positives.

At this moment, there is not a consumer for dead-letter queue, so we don´t expect that items decrease.

Answer 1

Hi @Jesus Arnas

Thank you for reaching out to Microsoft Q&A forum!

It sounds like you’re experiencing some unusual behavior with your Azure Service Bus dead-letter queue. Here are a few potential reasons and steps to investigate:

Message Expiry: If messages in the dead-letter queue have a time-to-live (TTL) set, they might be expiring and getting removed automatically. However, this shouldn’t cause them to reappear1.

Intermittent Consumers: Even if there isn’t a dedicated consumer for the dead-letter queue, check if there are any intermittent processes or scripts that might be accessing and processing these messages2.

Service Bus Operations: Sometimes, internal operations within Azure Service Bus might cause temporary fluctuations. Ensure that there are no automated tasks or maintenance activities scheduled that could affect the queue1.

Monitoring Tools: Verify the accuracy of the monitoring tools and dashboards. Sometimes, glitches or delays in data reporting can cause misleading spikes or drops2.

To get more detailed insights, you can use the Service Bus Explorer tool available in the Azure portal. This tool allows you to peek into the dead-letter queue and inspect the messages, including their custom properties and reasons for being dead-lettered2.