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We are trying to consume messages from DLQ of Service Bus using logic App with below settings.

Snapshot of Logic App with DLQ

But with these settings we are getting below error

Snapshot of error

To confirm if we are able to process messages from main subscription or not, selected the subscription type as "Main" and found that it works well and processes the messages.

Snapshot of Logic App With Main Queue

As it is working fine with Main Subscription, so it is not the issue of Message Forwarding at all, like it says in error message, but something else which is not clear from error message but happening behind the scene.

Any clue/help will be well appreciable.

Thanks in advance.

Rakesh Aggarwal
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1 Answers1

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The error message you're getting is stating that dead-letter queue is set to auto-forward messages to another entity. You can't have auto-forwarding enabled and receive messages manually (LogicApp) at the same time. Disable auto-forwarding on the dead-letter sub-queue of your subscription and that should resolve the problem.

Sean Feldman
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  • Actually in case of Topic/Subscriptions there is no facility of setting the auto-forwarding on dead-letter sub-queue. This facility is available only for Queues. Also it was working fine earlier, but suddenly it stopped and start creating the issue. – Rakesh Aggarwal Jul 18 '23 at 15:01
  • Azure Service Bus queues and subscriptions are very similar entities: both support dead-lettering, DLQ sub-queue, and auto-forwarding the main and DLQ queues. When a message is dead-lettered and auto-forwarded, ASB broker stamps the entity name it was auto-forwarded from. [See for yourself](https://pasteboard.co/X00937KFN1jx.jpg). – Sean Feldman Jul 18 '23 at 16:10
  • below is the configuration of subscription, where it is not working and it clearly shows that no forwarding is applied here on DLQ – Rakesh Aggarwal Jul 19 '23 at 06:01
  • Sorry, ignore my last comment on this and consider this one where, We further checked the configuration of subscription where it is not working and found that, property **forwardDeadLetteredMessagesTo** is null for this subscription. Today morning we observed one more strange thing about this subscription, that is, if we move messages from DLQ to main subscription using Service Bus Explorer then it is omitting the body of message, means size of message is in MBs in DLQ and after transfer to main subscription it is in 4-5 Bytes only and body is empty. – Rakesh Aggarwal Jul 19 '23 at 06:07
  • SBE does not support large messages as it's using an older SDK that was not designed to handle large messages. – Sean Feldman Jul 20 '23 at 03:05