403 error or null value while reading messages from Service Bus DLQ using Logic App/Azure Function

Question

403 error or null value while reading messages from Service Bus DLQ using Logic App/Azure Function

Rakesh Aggarwal 0

Few days back we added azure function to read messages from DLQ of Topic/Subscription and after processing few messages it started giving null as a value of message even messages are available in DLQ. Due to this it got stuck in DLQ and we are not able to process messages from DLQ.

To investigate it further we added the logic app workflow as well to process messages from DLQ and we are getting below error

User's image

Error message clearly says that, when auto forwarding is enabled then we can't read messages from topic.

But its very strange that in the same topic, we are able to read/process messages from another subscription, with no issues at all. Below is snapshot of configuration for the topic

User's image

We are now helpless in this regard as, no auto forwarding is applied and even it processed few messages using Azure Function and then suddenly stopped.

If any one is having some clue about the issue then kindly suggest.

Thanks in advance :)

1 answer

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Answer 1

MayankBargali-MSFT 70,936 Moderator

@Rakesh Aggarwal Thanks for reaching out.

When you are using topic subscription then the message is always sent to the topic, but the messages are consumed from the subscriptions that are created under the topic and not from the topic itself.

For more details you can refer to this document.

So, if you have enabled auto forwarding on any of the subscriptions under the topic then you cannot use any application/receiver to receive the messages from that particular subscription. That is the reason you are able to consume the messages from another subscription on the same topic.

You need to create another subscription with the same filter as your previous one so the new message can now be received from this new subscription.

For more details on auto forwarding, you can refer to this document.

Let me know if you have any queries or concerns.

Please "Accept Answer" if the answer is helpful so that it can help others in the community.

Rakesh Aggarwal 0 Reputation points

2023-07-18T11:05:03.6233333+00:00

Thanks for Quick response.

As we mentioned in original detail of issue, this problem started when we were processing messages using Azure Function, in starting it processed messages from both subscriptions and suddenly it stopped for one subscription and message started coming as null.

As mentioned, to further check the behavior of service we added logic app workflow and there as well it worked only on one and for other one it started giving mentioned error, which says "trigger can't be added on entity with auto forwarding enabled".

below are the screen shots of both subscriptions

Subscription having issues

Subscription it is working fine

In both cases, auto forwarding is disabled.
MayankBargali-MSFT 70,936 Reputation points Moderator

2023-07-18T11:48:58.4133333+00:00

@Rakesh Aggarwal Thanks for sharing the screenshot. Can you please confirm if your subscription name is same as your topic name? As per the error it says entity name i.e. sbtpbiometriahpr but I can only see your topic name in the screenshoot. Then in this case it looks like there is some issue with the subscription where the operation performed might be stuck. In case if you this is the test subscription then can you try deleting and recreating the subscription with the same name or try enabling and disabling the status of your subscription/enable the auto forwarding one time and disable it so the subscription can sync again.
Rakesh Aggarwal 0 Reputation points

2023-07-18T12:32:10.88+00:00

Hi Again,

As a further investigation, we added a new message to Subscription having issue and rather than selecting the subscription type "dead letter" selected "Main" in logic app workflow as below and found that it is working fine with main subscription but now with DLQ.
MayankBargali-MSFT 70,936 Reputation points Moderator

2023-07-24T04:58:23.7433333+00:00

@Rakesh Aggarwal Thank you for sharing your osbservation.
Rakesh Aggarwal 0 Reputation points

2023-07-24T06:21:07.9133333+00:00

This is to confirm that, topicName and subscriptionName are different in this case.

As per further investigation in this direction, we tried to Re-send these messages from DLQ to main subscription, so that we can process them from main subs at least, as things are working fine with main. But we observed that, after resending the message from DLQ to main, it is ommitting the body of message, means if in DLQ size of message is 50 MB then after resending it is becoming 4 Bytes only. From this we suspect that, whatever messages are left in DLQ now are either corrupt messages or these are not related to us, but are something else, which can't be processed at all.

Kindly suggest on this
MayankBargali-MSFT 70,936 Reputation points Moderator

2023-07-24T06:57:52.6366667+00:00

@Rakesh Aggarwal Can you send email an email with subject line “Attn:Mayank” to AzCommunity[at]Microsoft[dot]com referencing this thread along with your availability so I can quickly review it.
Rakesh Aggarwal 0 Reputation points

2023-08-02T10:26:21.53+00:00

Hi Again,

As we discussed that, we can't process messages with size more than 1 MB using Azure Function and Logic App, so we tried with .Net SDK as well, but found that same issue is there as well, message is coming as null.

Below is the code block we are using to process messages from DLQ using .Net Console Application.

MayankBargali-MSFT 70,936 Moderator

@Rakesh Aggarwal As discussed, we have used the different code using Azure Messaging ServiceBus SDK but we still observe the same issue that we are not able to consume the old messages from deadletter queue whereas the new messages to dead letter queue we are able to consume.

string connectionString = "";
            string topicName = "topicName";
            string subName = "subscriptionName/$DeadLetterQueue";

            var client = new ServiceBusClient(connectionString);
            var receiver = client.CreateReceiver(topicName, subName, new ServiceBusReceiverOptions
            {
                ReceiveMode = ServiceBusReceiveMode.PeekLock,
            });

 

            var message = await receiver.ReceiveMessageAsync();

 

            if (message != null)
            {
                var body = message.Body;
                // process the message body
                //await receiver.CompleteMessageAsync(message);
            }

It looks like these are the stuck messages and to troubleshoot it further we have raised the support request so the team can review the backend logs.

We will update this thread once the issue is resolved.

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403 error or null value while reading messages from Service Bus DLQ using Logic App/Azure Function

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