I am having problems connecting from Azure Flex Consumption Function App to Service Bus

Question

I have a flex consumption function app plan which has service bus connection string set in its app settings, however it does not seem to be consuming messages from Service bus. The service bus we use is a standard plan and the error we get is "MaxDeliveryCountExceeded". The app has a system assigned managed identity which has access to the service bus too. With the Flex Consumption Plans I am struggling to find ways to diagnose issues.

Answer 1

Hello @Chris Gray

This error occurs when the maximum number of delivery attempts for a message has been exceeded. To diagnose the issue, you can try the following 5 steps:

1. Check if the connection string for the Service Bus is correct and is set in the app settings of your Azure Function App. You can verify this by going to the Configuration section of your Function App and checking if the connection string is present.
2. Check if the managed identity of your Function App has the necessary permissions to access the Service Bus. You can verify this by going to the Access control (IAM) section of your Service Bus namespace and checking if the managed identity has the necessary permissions.
3. Check if the Function App is able to connect to the Service Bus by using the Service Bus Explorer tool. You can download the tool from the Azure portal and use it to connect to your Service Bus namespace. If you are able to connect and see the messages in the queue or topic, then the issue might be with your Function App.
4. Check if the Function App is able to receive messages from the Service Bus by using the Service Bus Explorer tool. You can send a test message to the queue or topic and check if the Function App is able to receive it. If the Function App is not able to receive the message, then the issue might be with the Function App code.
5. Check the Function App logs for any errors or exceptions related to the Service Bus connection or message consumption. You can view the logs by going to the Monitoring section of your Function App and selecting the Logs option.

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