CODEWITHSUNDEEP
c#sessionazureazureservicebus
Richard
Richard

Reputation: 1692

Calling Abandon on an Azure Service Bus re-queues the message at the back rather than the front of the queue

I'm using an Azure Service Bus Queue with Session based messaging enabled. To consume from the queue I register an IMessageSessionAsyncHandler and then process the message in the OnMessageAsync method.

This issue I'm seeing is that if I abandon a message for whatever reason, rather than being received again immediately, I receive the next message in the session and only after processing that message, do I receive the first message again (assuming only two messages in the session).

As an example, lets say I have a queue with 2 messages on it, both with the same SessionId. The two messages have sequence numbers of 1 and 2 respectively. I start receiving and get message with sequence 1, as expected. If I then abandon this message using message.Abandon (the reason for abandoning is irrelevant), I immediately get the next message in the session (sequence number 2). Only after handling (or abandoning) this second message, do I get the first message again.

This behaviour I'm seeing isn't what I'd expect from abandoning a message and isn't consistent with other ways of using the queue. I've tested this same example in the following scenarios

In both scenarios, I see the expected bahaviour, in that when I abandon a message it is always guaranteed to be the next message received, unless the max delivery count is exceeded and it is dead-lettered.

My question is this: Is the behaviour I'm seeing with the use of an IMessageSessionAsyncHandler expected, or is this a bug in the Service Bus Library? If this is not a bug, can anyone give me an explaination for why this behaves different to the other ways of receiving?

Upvotes: 2

Views: 1787

Answers (1)

Padma Aradhyula
Padma Aradhyula

Reputation: 201

When you Register a session handler on the Queueclient, Prefetch is turned on internally to improve latency and throughput of the receivers. Unfortunately for the IMessageSessionAsyncHandler scenario this behavior cannot be overriden. One option is to abandon the Session itself when you encounter a message in a session which needs to be abandoned, this will ensure that the messages are delivered in order.

Upvotes: 1

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