Azure WebJob with Queue triggered fired multiple times

Question

I have a console app that pushes a lot of messages in parallel to an Azure Storage Queue. There's a continuous triggered Azure WebJob that invokes whenever a message gets added into that queue. In one of the scenarios, I had added 300 items to queue , 100 each in three different threads. Since there are only 300 messages in the queue, the WebJob should ideally be invoked only 300 times. But I could see it has invoked 308 times. What could be the reason for it? Also note that the additional trigger count is not predictable. Sometimes it may be 306 or 310 etc.

I have tried posting messages sequentially by removing Parallel.Invoke to check if its related to parallel processing, but the issue is still there. I am debugging the issue by running the WebJob project in local.

Answer 1

It is possible that exceptions occurred during processing of some messages. If a message fails to process successfully, it will be retried. Each message has a dequeueCount. If memory serves, the default for a Queue Trigger is five attempts.

Try running locally and watching the output window. Or, you can check the webjob logs on your live Azure instance to see if a message was retried.