Timer trigger Azure Function stopped working without any changes

Question

I have an Azure Function that has both Timer Trigger and Service Bus Trigger functions. In Portal Azure configuration of that AF, I have the correct storage account connection string AzureWebJobsStorage. There were no changes in ARM of both resources, everything was working properly until few days ago. Now only Service Bus Trigger functions are working, but not Timer Trigger ones.

Connecting string to storage is 100% correct, I've even regenerated the access key.

I've found logs for starting Host:

2021-05-25T15:23:10.703 [Error] The listener for function 'XXX' was unable to start.
Microsoft.Azure.WebJobs.Host.Listeners.FunctionListenerException : The listener for function 'XXX' was unable to start. ---> System.InvalidOperationException : Could not create BlobServiceClient to obtain the BlobContainerClient using Connection: Storage
   at Microsoft.Azure.WebJobs.Script.AzureStorageProvider.GetBlobContainerClient() at D:\a\1\s\src\WebJobs.Script\StorageProvider\AzureStorageProvider.cs : 69
   at Microsoft.Azure.WebJobs.Extensions.Timers.AzureStorageScheduleMonitor.GetStatusBlobReference(String timerName) at D:\a\1\s\src\WebJobs.Script\Timer\AzureStorageScheduleMonitor.cs : 146
   at async Microsoft.Azure.WebJobs.Extensions.Timers.AzureStorageScheduleMonitor.GetStatusAsync(String timerName)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at async Microsoft.Azure.WebJobs.Extensions.Timers.Listeners.TimerListener.StartAsync(CancellationToken cancellationToken) at C:\azure-webjobs-sdk-extensions\src\WebJobs.Extensions\Extensions\Timers\Listener\TimerListener.cs : 99
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at async Microsoft.Azure.WebJobs.Host.Listeners.SingletonListener.StartAsync(CancellationToken cancellationToken) at C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Singleton\SingletonListener.cs : 70
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at async Microsoft.Azure.WebJobs.Host.Listeners.FunctionListener.StartAsync(??) at C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Listeners\FunctionListener.cs : 68
   End of inner exception

I've checked diagnostics in New Support Request -> Solutions and everything is ok. Also, the same error appears (but less descriptive) when trying to start AF from Visual Studio using the same configuration as from Portal Azure.

What could be wrong? What more I could check to find the solution for this problem?

Answer 1

There is a possible regression in the latest function host release(3.0.15733.0). Please set the app setting FUNCTION_EXTENSION_VERSION=3.0.15584.0 (previous function runtime version).

The regression will be fixed in the next function host release: https://github.com/Azure/azure-functions-host/releases

Answer 2

Earlier we have updated the FUNCTION_EXTENSION_VERSION from ~3 to 3.0.15584.0, and looks like the issue with 3.0.15733.0 was fixed and I could see latest version is 3.0.15960 (https://github.com/Azure/azure-functions-host/releases)

However, since morning the timer trigger is failing again, so I tried to revert the FUNCTION_EXTENSION_VERSION to ~3, but no luck as function is throwing the same error. But timer trigger is working fine if we set the FUNCTION_EXTENSION_VERSION to 3.0.15960.0.