azure-webjobs-sdk-extensions: TimerTrigger in Webjobs SDK does not support managed identity

We have a project

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <RootNamespace>Vlk.HrServices.Api.HrIntegration</RootNamespace>
    <UserSecretsId>2b57ac3c-5825-44df-ac93-078f754f2c38</UserSecretsId>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="AspNetCore.HealthChecks.UI.Client" Version="6.0.2" />
    <PackageReference Include="Azure.Extensions.AspNetCore.Configuration.Secrets" Version="1.2.1" />
    <PackageReference Include="Azure.Storage.Common" Version="12.12.0" />
    <PackageReference Include="Azure.Storage.Queues" Version="12.11.0" />
    <PackageReference Include="CsvHelper" Version="27.2.1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions" Version="4.0.1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.Storage" Version="5.0.1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.Storage.Queues" Version="5.0.1" />
    <PackageReference Include="Microsoft.Extensions.Hosting" Version="6.0.0" />
    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="6.0.0" />
    <PackageReference Include="Serilog.AspNetCore" Version="4.1.0" />
    <PackageReference Include="Serilog.Sinks.Console" Version="4.0.1" />
  </ItemGroup>

In this project we have configured webjobs as follows, in Program.cs

builder.Host.ConfigureWebJobs(b =>
{
    b.AddAzureStorageCoreServices();
    b.AddAzureStorageBlobs(options => { options.MaxDegreeOfParallelism = 1; });
    b.AddAzureStorageQueues(options =>
    {
        options.BatchSize = 1;
        options.MaxDequeueCount = 2;
    });
    b.AddTimers();
});

We have been using BlobTrigger and QueueTrigger succesfully, using the simplified storage account configuration in appsettings.json

"AzureWebJobsStorage": {
    "accountName": "hrintegrationtstsa"
  },

We are using managed identity for the webapp and have assigned proper roles to the webapp’s identity and everything is working fine.

Now we have the need to add TimerTrigger functionality to this project. However it seems that the TimerTrigger is not compatible with the connection information in our appsettings.json. On startup it complains about a null connectionstring.

[14:33:19 DBG] The 'RunAsync' timer is using the schedule 'Cron: '0 0 0,4,8,12,16,20 * * 1-5'' and the local time zone: '(UTC+01:00) Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna'
[14:33:19 ERR] The listener for function 'NsExportSubscriber.RunAsync' was unable to start.
Microsoft.Azure.WebJobs.Host.Listeners.FunctionListenerException: The listener for function 'NsExportSubscriber.RunAsync' was unable to start.
 ---> System.ArgumentNullException: Value cannot be null. (Parameter 'connectionString')
   at Microsoft.Azure.Storage.CloudStorageAccount.Parse(String connectionString)
   at Microsoft.Azure.WebJobs.Extensions.Timers.StorageScheduleMonitor.get_TimerStatusDirectory() in C:\azure-webjobs-sdk-extensions\src\WebJobs.Extensions\Extensions\Timers\Scheduling\StorageScheduleMonitor.cs:line 73
   at Microsoft.Azure.WebJobs.Extensions.Timers.StorageScheduleMonitor.GetStatusBlobReference(String timerName) in C:\azure-webjobs-sdk-extensions\src\WebJobs.Extensions\Extensions\Timers\Scheduling\StorageScheduleMonitor.cs:line 144
   at Microsoft.Azure.WebJobs.Extensions.Timers.StorageScheduleMonitor.GetStatusAsync(String timerName)
   at Microsoft.Azure.WebJobs.Extensions.Timers.Listeners.TimerListener.StartAsync(CancellationToken cancellationToken) in C:\azure-webjobs-sdk-extensions\src\WebJobs.Extensions\Extensions\Timers\Listener\TimerListener.cs:line 99
   at Microsoft.Azure.WebJobs.Host.Listeners.SingletonListener.StartAsync(CancellationToken cancellationToken) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Singleton\SingletonListener.cs:line 70
   at Microsoft.Azure.WebJobs.Host.Listeners.FunctionListener.StartAsync(CancellationToken cancellationToken, Boolean allowRetry) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Listeners\FunctionListener.cs:line 68

Now, if we add a connection string to appsettings.json like this:

"ConnectionStrings": {
    "AzureWebJobsStorage": "DefaultEndpointsProtocol=https;AccountName=hrintegrationtstsa;AccountKey=**redacted**;EndpointSuffix=core.windows.net"
  },

then the projects starts ok, and the TimerTrigger executes as expected.

The TimerTrigger is in Microsoft.Azure.Webjobs.Extensions and we are at version 4.0.1 (latest)

Can you please comment on our observation? We would like to have this managed identity connection work for TimerTrigger as well.

Kind regards, Chris