Enable Snapshot Debugger for .NET and .NET Core apps in Azure Functions

Snapshot Debugger currently works for ASP.NET and ASP.NET Core apps that are running on Azure Functions on Windows service plans.

We recommend that you run your application on the Basic service tier or higher when you use Snapshot Debugger.

For most applications, the Free and Shared service tiers don't have enough memory or disk space to save snapshots.

Prerequisite

Enable Application Insights monitoring in your Functions app

Enable Snapshot Debugger

To enable Snapshot Debugger in your Functions app, add the snapshotConfiguration property to your host.json file and redeploy your function. For example:

{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "snapshotConfiguration": {
        "isEnabled": true
      }
    }
  }
}

Snapshot Debugger is preinstalled as part of the Azure Functions runtime and is disabled by default. Because it's included in the runtime, you don't need to add extra NuGet packages or application settings.

In the simple .NET Core Function app example that follows, .csproj, {Your}Function.cs, and host.json have Snapshot Debugger enabled:

Project.csproj

<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <AzureFunctionsVersion>v2</AzureFunctionsVersion>
</PropertyGroup>
<ItemGroup>
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="1.0.31" />
</ItemGroup>
<ItemGroup>
    <None Update="host.json">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
</ItemGroup>
</Project>

{Your}Function.cs

using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;

namespace SnapshotCollectorAzureFunction
{
    public static class ExceptionFunction
    {
        [FunctionName("ExceptionFunction")]
        public static Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Function, "get", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            throw new NotImplementedException("Dummy");
        }
    }
}

Host.json

{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "samplingExcludedTypes": "Request",
      "samplingSettings": {
        "isEnabled": true
      },
      "snapshotConfiguration": {
        "isEnabled": true
      }
    }
  }
}

Enable Snapshot Debugger for other clouds

Currently, the only regions that require endpoint modifications are Azure Government and Microsoft Azure operated by 21Vianet.

The following example shows the host.json updated with the US Government Cloud agent endpoint:

{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "samplingExcludedTypes": "Request",
      "samplingSettings": {
        "isEnabled": true
      },
      "snapshotConfiguration": {
        "isEnabled": true,
        "agentEndpoint": "https://snapshot.monitor.azure.us"
      }
    }
  }
}

Here are the supported overrides of the Snapshot Debugger agent endpoint:

Property	US Government Cloud	China Cloud
AgentEndpoint	https://snapshot.monitor.azure.us	https://snapshot.monitor.azure.cn

Disable Snapshot Debugger

To disable Snapshot Debugger in your Functions app, update your host.json file by setting the snapshotConfiguration.isEnabled property to false.

{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "snapshotConfiguration": {
        "isEnabled": false
      }
    }
  }
}

We recommend that you have Snapshot Debugger enabled on all your apps to ease diagnostics of application exceptions.

Next steps

• Generate traffic to your application that can trigger an exception. Then wait 10 to 15 minutes for snapshots to be sent to the Application Insights instance.
• View snapshots in the Azure portal.
• Customize Snapshot Debugger configuration based on your use case on your Functions app. For more information, see Snapshot configuration in host.json.
• For help with troubleshooting Snapshot Debugger issues, see Snapshot Debugger troubleshooting.