Triggering Durable Function throws Null Reference exception

Question

I have the following setup to test my Durable Function.

public class TestDurableFunction
{
    private readonly ITestRepository _testRepository;

    public TestDurableFunction(ITestRepository testRepository)
    {
        _testRepository = testRepository; // needed for later use
    }
    
    [FunctionName("TimerTrigger")]
    public async Task Run([TimerTrigger("0 1 * * *", RunOnStartup = true)] TimerInfo myTimer, [DurableClient] IDurableClient starter, ILogger logger)
    {
        try
        {
            await starter.StartNewAsync("OrchestrateSavings", null);
        }
        catch (Exception exception)
        {
            logger.LogFunctionError(nameof(Run), nameof(TestDurableFunction), exception);
        }
    }

    [FunctionName("OrchestrateTest")]
    public async Task<int> OrchestrateTest([OrchestrationTrigger] IDurableOrchestrationContext context)
    {
        await Task.CompletedTask;
        return 10;
    }
}

When I start this function locally, then the TimerTrigger function starts with no problems. This function then calls my OrchestrateTest Durable Function.

But that immediately throws the following error in the Command Prompt window:

Microsoft.Azure.WebJobs.Script.WebHost: Unable to load metadata for function 'OrchestrateTest'. Function 'OrchestrateTest (Orchestrator)' was aborted. Reason: An internal error occurred while attempting to execute this function. The execution will be aborted and retried. Details: System.NullReferenceException: Object reference not set to an instance of an object.

Anyone any idea what the issue could be?

Anyone searching for this error message, you get the same message if you missout [FunctionName("xxx")] and have RunOnStartup = True on the method — Rob Sedgwick
– Rob Sedgwick, Commented May 18, 2023 at 20:59

user1672994 · Accepted Answer · 2021-07-12 16:48:03Z

2

As per your code the orchestrator function you are invoking is OrchestrateSavings; however there is not orchestrator function registered with that name. As per posted code the orchestrator function name is OrchestrateTest. So change the line to

await starter.StartNewAsync("OrchestrateTest", null);

in the Run method.

answered Jul 12, 2021 at 16:48

user1672994

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