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

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 2

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();