Azure function app on consumption plan not processing messages from service bus queue

Question

Azure function app on consumption plan not processing messages from service bus queue

Mike Taylor 25

Hello,

I'm encountering an issue with my C# .NET Isolated function app (consumption plan) and its interaction with an Azure Service Bus queue. Specifically, one particular queue is not triggering the associated function app when messages are placed into it, while other queues function correctly.

Here's a breakdown of the situation:

Setup:
- C# .NET Isolated function app (consumption plan)
  - Multiple Azure Service Bus queues (approximately 10)
    - One specific queue is failing to trigger the function app.
      - The rest of the queues are triggering the function app correctly.
      - Problem:
        
        Messages placed into the problematic queue are not being processed by the function app.
        
        Other queues are working as expected.
        
        Troubleshooting steps taken:
        
        Verified that messages are indeed being placed into the queue.
        
        I've used the Azure Portal "Diagnose and solve problems" tool, but it did not provide a solution.

Could anyone offer suggestions on how to further diagnose and resolve this issue? I'm looking for guidance on potential areas to investigate, such as:

Specific logs or metrics to examine for the problematic queue and function app.
Common configuration issues that might cause this behavior.
Any recommended troubleshooting steps beyond the Azure Portal's diagnostics.

Thank you for your assistance.

Mike

Shireesha Eeraboina 1,980 Reputation points Microsoft External Staff

2025-03-11T07:14:16.5666667+00:00
Hi Mike Taylor,

The issue with the Service Bus queue not triggering your Azure Function app could be caused by several different factors. Here’s how you can troubleshoot the situation:

Make sure the problematic queue is correctly set up in the ServiceBusTrigger attribute of your function.

Confirm that the connection string and queue name are accurate.

Use Application Insights or Azure Monitor to look for any errors associated with the problematic queue.

Ensure that the Service Bus namespace has the correct Shared Access Policy with the necessary permissions.

Restart your Function App and redeploy it to ensure that all configurations are applied correctly.

Review the host.json file for settings like maxConcurrentCalls or prefetchCount that could impact message processing.

For more detailed guidance, refer to the Azure Service Bus Trigger Troubleshooting and Service Bus Monitoring

I hope this answers your query! Let me know if you require any additional help or clarification.
Mike Taylor 25 Reputation points

2025-03-11T07:20:29.21+00:00

Hi Shireesha Eeraboina, thank you for getting back to me.

So prior to a recent code change, where we were handling less messages, this was working fine with no problems for the past year or so. Proper strange how it suddenly isn't working as expected.

Regarding the host.json file, this hasn't changed in the recent set of changes.

I've tried looking at Application Insights and couldn't find anything that would highlight the issue. I haven't tried Azure monitor so will give that a go.

Thank you

Mike
Mike Taylor 25 Reputation points

2025-03-11T09:55:09.8233333+00:00

Using the Monitor that you suggested, I've found this interesting metric, User Errors. Any idea on why all queue would increase like that? We've only deployed one recent change to one service, I wouldn't expect this affect all of the other services.
Mike Taylor 25 Reputation points

2025-03-11T09:57:33.0466667+00:00

After looking at the service bus monitor we've identified a massive increase in User Errors. When looking at the metrics to the function apps, none of them are erroring. Considering we've only published 1 change which would affect one queue, why are all of the queues generating a lot more User Errors?
Mike Taylor 25 Reputation points

2025-03-11T13:56:03.97+00:00

This has now been resolved. This one properly got us, and sinked a good 4 days on it. Turns out Microsoft did some updates on the 05/03/2025. This caused our Service Bus to be re-created, I've got no idea why or how this happened, but it happened at 1:50AM UTC.
The service bus was originally created about 9 months ago, but when checking the properties on the azure dashboard, it said it was only created a couple of days ago. This was defo not the case.

Resolution to this, adjusting the azure queue policy for the function app to have a managed capability.

Accepted answer

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Shireesha Eeraboina 1,980 Reputation points Microsoft External Staff

2025-03-11T07:14:16.5666667+00:00

Hi Mike Taylor,

The issue with the Service Bus queue not triggering your Azure Function app could be caused by several different factors. Here’s how you can troubleshoot the situation:

Make sure the problematic queue is correctly set up in the ServiceBusTrigger attribute of your function.

Confirm that the connection string and queue name are accurate.

Use Application Insights or Azure Monitor to look for any errors associated with the problematic queue.

Ensure that the Service Bus namespace has the correct Shared Access Policy with the necessary permissions.

Restart your Function App and redeploy it to ensure that all configurations are applied correctly.

Review the host.json file for settings like maxConcurrentCalls or prefetchCount that could impact message processing.

For more detailed guidance, refer to the Azure Service Bus Trigger Troubleshooting and Service Bus Monitoring

I hope this answers your query! Let me know if you require any additional help or clarification.
Mike Taylor 25 Reputation points

2025-03-11T07:20:29.21+00:00

Hi Shireesha Eeraboina, thank you for getting back to me.

So prior to a recent code change, where we were handling less messages, this was working fine with no problems for the past year or so. Proper strange how it suddenly isn't working as expected.

Regarding the host.json file, this hasn't changed in the recent set of changes.

I've tried looking at Application Insights and couldn't find anything that would highlight the issue. I haven't tried Azure monitor so will give that a go.

Thank you

Mike
Mike Taylor 25 Reputation points

2025-03-11T09:55:09.8233333+00:00

Using the Monitor that you suggested, I've found this interesting metric, User Errors. Any idea on why all queue would increase like that? We've only deployed one recent change to one service, I wouldn't expect this affect all of the other services.
Mike Taylor 25 Reputation points

2025-03-11T09:57:33.0466667+00:00

After looking at the service bus monitor we've identified a massive increase in User Errors. When looking at the metrics to the function apps, none of them are erroring. Considering we've only published 1 change which would affect one queue, why are all of the queues generating a lot more User Errors?
Mike Taylor 25 Reputation points

2025-03-11T13:56:03.97+00:00

This has now been resolved. This one properly got us, and sinked a good 4 days on it. Turns out Microsoft did some updates on the 05/03/2025. This caused our Service Bus to be re-created, I've got no idea why or how this happened, but it happened at 1:50AM UTC.
The service bus was originally created about 9 months ago, but when checking the properties on the azure dashboard, it said it was only created a couple of days ago. This was defo not the case.

Resolution to this, adjusting the azure queue policy for the function app to have a managed capability.

Answer 1

Hi @Mike Taylor ,

Thank you for your patience and for sharing your feedback on the Q&A community platform. I’m glad to hear that you were able to resolve your issue, and I appreciate you sharing your solution! Your contribution is valuable and can help others in the community facing similar challenges.

As per the Microsoft Q&A community policy, "The question author cannot accept their own answer. They can only accept answers by others"

I’m reposting your solution here so you can mark it as accepted if it resolves your query:

"Modifying the Azure queue policy for the function app to enable managed capabilities".

If you have any other questions, please let me know. Thank you again for your time and patience throughout this issue.

Please don’t forget to Accept Answer and Yes for "was this answer helpful" wherever the information provided helps you, this can be beneficial to other community members.

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Azure function app on consumption plan not processing messages from service bus queue

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