Why I get error in Azure Function when use async/Task, but when use these in Console App, there is no error?

Question

This is how I use async/Task in Console App:

using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace CaseDurableFunctionConsole
{

    class Program
    {
        static async Task<List<string>> RunOrchestrator()
        {
            Console.WriteLine("Hello World!");
            Console.ReadLine();
            var outputs = new List<string>();
            return outputs;
        }

        static void Main(string[] args)
        {
            RunOrchestrator();
        }
    }
}

This works well and this is the output:

enter image description here

(Even without using await, it shows the right result.)

But when I use async/Task in Azure Functions, like this:

[FunctionName("Function1")]
public static async Task<List<string>> RunOrchestrator(
    [OrchestrationClient] DurableOrchestrationClient orchestrationClient)
{
    var outputs = new List<string>();
    await Task.Delay(1);
    return outputs;
}

Then it comes up with an error after started.

[2019/11/25 5:50:50] Error indexing method 'Function1' [2019/11/25 5:50:50] Microsoft.Azure.WebJobs.Host: Error indexing method 'Function1'. Microsoft.Azure.WebJobs.Host: Functions must return Task or void, have a binding attribute for the return value, or be triggered by a binding that natively supports return values.

[2019/11/25 5:50:56] The 'Function1' function is in error: Microsoft.Azure.WebJobs.Host: Error indexing method 'Function1'. Microsoft.Azure.WebJobs.Host: Functions must return Task or void, have a binding attribute for the return value, or be triggered by a binding that natively supports return values.

How can I fix this by modify my Function Code?

Paulo Morgado · Accepted Answer · 2019-11-25 09:10:51Z

1

This has nothing to do with async-await.

The log message states that, for that binding, the method should return Task or void and your method returns Task<List<string>>.

Your function method does not equate to the RunOrchestrator method in your console application. It equates to the Main method.

answered Nov 25, 2019 at 9:10

Paulo Morgado

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2 Comments

Frank Campbell Over a year ago

Thank you for reply. I feel that you should be right, but how can I return Task? I am a little dizzy about that.

Paulo Morgado Over a year ago

Have you tried just making the method signature public static async Task RunOrchestrator([OrchestrationClient] DurableOrchestrationClient orchestrationClient)?

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

Checked the documentation, here is the reason:

Orchestrations can schedule durable timers to implement delays or to set up timeout handling on async actions. Use durable timers in orchestrator functions instead of Thread.Sleep and Task.Delay (C#) or setTimeout() and setInterval() (JavaScript).

For more information and for examples, see the Durable timers article.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Nov 25, 2019 at 8:01

Jack Jia

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2 Comments

Frank Campbell Over a year ago

Hi, Jack. Do you have any suggestions of how to modify my code? Actually, I don't know how to modify the code to avoid this problem.

Jack Jia Over a year ago

Check the sample: Orchestrator.cs

Peter · Accepted Answer · 2022-12-15 17:41:38Z

0

Due to replay constraints of orchestrators, you mustn't await anything other than the orchestration context, or use sleep methods.

To wait, in a durable "replay" safe way, try:

await orchestrator.CreateTimer(orchestrator.CurrentUtcDateTime.AddMinutes(15), CancellationToken.None);

Also, you don't appear to have implemented an orchestration trigger function correctly. You need a trigger parameter such as:

[OrchestrationTrigger] IDurableOrchestrationContext orchestrator

answered Dec 15, 2022 at 17:41

Peter

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