MessageLockLostException after moving BrokeredMessage to dead letter in Azure Function v1

Question

I have a Azure Function v1 triggered via Service Bus topic. If there happens any error, I put the BrokeredMessage to dead letter. It seems to work but after that I see following in Function's log streaming:

2019-11-19T10:49:31.382 [Error] MessageReceiver error (Action=Complete): Microsoft.ServiceBus.Messaging.MessageLockLostException: The lock supplied is invalid. Either the lock expired, or the message has already been removed from the queue.

Here is what how I am putting BrokeredMessage to dead letter:

myBrokeredMessage.DeadLetter(deadLetterReason, exception.Message);
// after this I have tried following but doesn't work:
// 1. do nothing
// 2. myBrokeredMessage.Complete();
// 3. myBrokeredMessage.Abandon();

My Function is running fine. But after it has run and executed above code, that error appears to log streaming. It seems doing what I want (putting BrokeredMessage to dead letter queue), but that error doesn't seem nice and I want to fix it. I guess there is some kind of lock that I'm not handling correctly.

What should I do to fix that error?

Answer 1

What should I do to fix that error?

This is more of a warning than an error. The way Functions are designed is that by default the function completes or dead-letters the message. If you take control over what happens to the incoming message, Functions runtime doesn't it and still tries to apply the logic of completion as from its perspective there was no exception thrown from the user code and therefore the incoming message should be considered successfully processed and be completed.

With Functions 2.x there's a host setting that you could turn on to allow manual completion and disable the automatic completion. That is not available in v1.0, so you'll have to ignore the logged error. Or, alternatively, upgrade to 2.x.