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 or higher service tiers when using Snapshot Debugger. For most applications:

• The Free and Shared service tiers don't have enough memory or disk space to save snapshots.
• The Consumption tier isn't currently available for Snapshot Debugger.

Snapshot Debugger is preinstalled as part of the Azure Functions runtime, so you don't need to add extra NuGet packages or application settings.

Enable Application Insights monitoring in your Functions app.

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
      }
    }
  }
}

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.

You can verify that Snapshot Debugger has been enabled by checking your .NET function app files. For example, in the following simple .NET function app, the .csproj, {Your}Function.cs, and host.json of your .NET application show Snapshot Debugger as 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
      }
    }
  }
}

Currently the regions in Azure operated by 21Vianet require endpoint modifications.

The following example shows the host.json updated with the Azure operated by 21Vianet Cloud agent endpoint:

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

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

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
      }
    }
  }
}

• 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.
• Troubleshoot Snapshot Debugger issues.