Azure Function - Failed to start a new language worker for runtime: dotnet-isolated

Question

I have a dotnet 5 function app that I've been building and deploying from a devops pipeline for a couple of weeks.

Following the most recent release, I see the following error in App Insights:

Exception type System.TimeoutException Exception message The operation has timed out. LogLevel Error prop__{OriginalFormat} Failed to start a new language worker for runtime: dotnet-isolated. Category Microsoft.Azure.WebJobs.Script.Workers.Rpc.RpcFunctionInvocationDispatcher System.TimeoutException: The operation has timed out. at Microsoft.Azure.WebJobs.Script.Grpc.GrpcWorkerChannel.StartWorkerProcessAsync()

csproj file:

<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
    <Nullable>enable</Nullable>
    <UserSecretsId>4f786da6-0d47-4ccc-b343-638a6e34e1cf</UserSecretsId>
  </PropertyGroup>

  <ItemGroup>
    <None Remove="local.settings.json" />
  </ItemGroup>

  <ItemGroup>
    <Content Include="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </Content>
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Mvc.Abstractions" Version="2.2.0" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc.Core" Version="2.2.5" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.2.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Abstractions" Version="1.0.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.0.13" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Storage" Version="4.0.4" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.0.3" />
    <PackageReference Include="Microsoft.Azure.Services.AppAuthentication" Version="1.6.1" />
    <PackageReference Include="Microsoft.Data.SqlClient" Version="3.0.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.UserSecrets" Version="5.0.0" />
    <PackageReference Include="NSwag.AspNetCore" Version="13.11.1" />
    <PackageReference Include="Serilog.AspNetCore" Version="4.1.0" />
    <PackageReference Include="Serilog.Sinks.ApplicationInsights" Version="3.1.0" />
    <PackageReference Include="Serilog.Sinks.MSSqlServer" Version="5.6.0" />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\infrastructure\SmsRouter.GovNotify\SmsRouter.GovNotify.csproj" />
    <ProjectReference Include="..\SmsRouter.Infrastructure\SmsRouter.EntityFramework.csproj" />
    <ProjectReference Include="..\SmsRouter.Utrn\SmsRouter.Utrn.csproj" />
  </ItemGroup>

  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
  </ItemGroup>

</Project>

host.json:

{
  "version": "2.0"
}

Function App Configuration:

[
  {
    "name": "APPINSIGHTS_INSTRUMENTATIONKEY",
    "value": "<my key is here>",
    "slotSetting": true
  },
  {
    "name": "AzureWebJobsStorage",
    "value": "DefaultEndpointsProtocol=https;AccountName=storesmsroutermsdn;AccountKey=<my key is here>;EndpointSuffix=core.windows.net",
    "slotSetting": false
  },
  {
    "name": "FUNCTIONS_EXTENSION_VERSION",
    "value": "~3",
    "slotSetting": false
  },
  {
    "name": "FUNCTIONS_WORKER_RUNTIME",
    "value": "dotnet-isolated",
    "slotSetting": false
  },
  {
    "name": "WEBSITE_CONTENTAZUREFILECONNECTIONSTRING",
    "value": "DefaultEndpointsProtocol=https;AccountName=storesmsroutermsdn;AccountKey=<my key is here>;EndpointSuffix=core.windows.net",
    "slotSetting": false
  },
  {
    "name": "WEBSITE_CONTENTSHARE",
    "value": "func-smsrouter-msdn-01b300",
    "slotSetting": false
  },
  {
    "name": "WEBSITE_ENABLE_SYNC_UPDATE_SITE",
    "value": "true",
    "slotSetting": false
  },
  {
    "name": "WEBSITE_RUN_FROM_PACKAGE",
    "value": "1",
    "slotSetting": false
  }
]

Function Definition

[Function("HttpExample")]
    public static HttpResponseData Run([HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequestData req,
        FunctionContext executionContext)
    {
        var response = req.CreateResponse(HttpStatusCode.OK);
        response.Headers.Add("Content-Type", "text/plain; charset=utf-8");

        response.WriteString("Welcome to Azure Functions!");

        return response;
    }

Has anyone else run into this problem?

Note: I have now created a support ticket for this via the Azure Portal - the id is 2106280050000196. Github issue here

Edit: Following the suggestion from @Kaylan, I used Azure CLI to create a new function app with --runtime dotnet-isolated param. I then deployed my functions into this (using devops pipeline with the Deploy Azure Function task) but I'm afraid I continue to see the same error.

I've also tried deploying to a fixed app service plan (rather than consumption) but continued to hit the same problem.

Answer 1

I was just dealing with the same problem. I finally fixed it by adding .ConfigureFunctionsWorkerDefaults() to my Program.cs file. I had removed it by accident.

I guess what I'm saying is, make sure you have .ConfigureFunctionsWorkerDefaults() in your Program.cs file. Here's an example:

using DataApi.AzureFunctions.Throttled;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureAppConfiguration(configBuilder => configBuilder.AddEnvironmentVariables())
    .ConfigureFunctionsWorkerDefaults() // <---- OMITTING THIS IS ONE POSSIBLE CAUSE OF THE ERROR "Failed to start a new language worker for runtime: dotnet-isolated."
    .ConfigureServices(Startup.Configure)
    .UseDefaultServiceProvider((_, options) =>
    {
        options.ValidateScopes = true;
        options.ValidateOnBuild = true;
    })
    .Build();

await host.RunAsync();

Answer 2

Whatever you do, with Azure App Services and Function Apps, always, always, triple check you have all your Configuration Settings complete and typo-free. A missing or misspelled setting can cause start up and dependency injection problems with cryptic messages like this one. Also, if you are using staging slots, make sure they either also have all their configuration settings correct, or keep the staging slots stopped.

Answer 3

When you make some change that utterly destroy the app before it even starts, and have no idea what is causing this disaster.

---

If your function app is on Linux

I don't know, good luck? You can see logs of processes from Kudu when the app starts, which might help.

---

If your function app is on Windows

• Open Kudu Console (Your Functions App > Advanced Tools > Go)
• From the top menus, Debug Console > CMD
• Navigate and open \home\LogFiles\eventlog.xml
  • note that the console opens at \home
• Scroll to the bottom to see the latest error

If the file is huge and you have no idea which one is your error, you can delete the file, then restart the functions app. New logs will be populated.

Answer 4

I got this propblem because I'd moved form a "normal" dotnet service and needed to tweak the FUNCTIONS_WORKER_RUNTIME from dotnet to dotnet-isolated:

local.settings.json

{
  "IsEncrypted": false,
  "Values": {

    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    ....

  }
}

Answer 5

I have tried multiple things for this issue, but what solved my problem is cleaning existing storage account for function app. I got that information from here https://github.com/Azure/azure-functions-dotnet-worker/issues/434#issuecomment-973408898

Answer 6

Please make the below changes to your host.json file to include extensionBundle

{
  "version": "2.0",
    "extensionBundle": {
      "id": "Microsoft.Azure.Functions.ExtensionBundle",
      "version": "[2.*, 3.0.0)"
    }
  }
}

Upgrade to Microsoft.Azure.Functions.Worker version 1.3.0 or higher

Install-Package Microsoft.Azure.Functions.Worker -Version 1.3.0

Ensure that the appropriate runtime is specified while creating the Function App.

az functionapp create --consumption-plan-location westus --name <FunctionAppName> --resource-group <ResourceGroupName> --runtime dotnet-isolated --runtime-version 5.0 --functions-version 3 --storage-account <StorageAccountName>

Answer 7

I just ran a NuGet package update for:

• Microsoft.Azure.Functions.Worker v1.3.0 → v1.4.0
• Microsoft.Azure.Functions.Worker.sdk v1.0.3 → v1.0.4

This seems to have solved the problem.

Answer 8

The reason that I got this error was due to a missing DBContext constructor. The error message seems entirely irrelevant and a complete red herring so hopefully this will help somebody who has the same issue.

I am using Entity Framework Core for MySQL. For some reason EF does not work if the constructor which accepts a DbContextOptions parameter is present. Each time I add a migration I comment it out. This last time I forgot to uncomment it and published the Function App to Azure. When I attempted to run the function I got this same error.

public class MyContext: DbContext
    {
        // while doing ef migrations we need to comment out this constructor below
       
        public MyContext(DbContextOptions<MyContext> options) : base(options)
        {
        }
   
        public MyContext()
        {

        }

I

Answer 9

I had the same issue, and any attempts to change Microsoft.Azure.Functions.Worker version as mainly suggested in most similar solution doesn't bring success.

The main root cause is timeout. And finally i found a solution. In my case

 .ConfigureServices(Startup.Configure)

takes a couple of second, due to the specific of the project, auditing etc. Changes in my Startup.Configure to run without delay and as much as possible faster. Bring positive result. Problem disappears on all versions of worker