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

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

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 3

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 4

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 5

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 them stopped.

Answer 6

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.