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

  • Article

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

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

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

Prerequisites

Enable Snapshot Debugger

If you're running a different type of Azure service, here are instructions for enabling Snapshot Debugger on other supported platforms:

To enable Snapshot Debugger in your Function app, you have to update your host.json file by adding the property snapshotConfiguration as defined below and redeploy your function.

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

Snapshot Debugger is pre-installed as part of the Azure Functions runtime, which by default it's disabled.

Since Snapshot Debugger it's included in the Azure Functions runtime, it isn't needed to add extra NuGet packages nor application settings.

Just as reference, for a simple Function app (.NET Core), below is how it will look the .csproj, {Your}Function.cs, and host.json after enabled Snapshot Debugger on it.

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>

Function class

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 file

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

Enable Snapshot Debugger for china cloud

Below is an example of 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"
      }
    }
  }
}

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

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

Disable Snapshot Debugger

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

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

We recommend 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 Function app. For more info, see snapshot configuration in host.json.
  • For help with troubleshooting Snapshot Debugger issues, see Snapshot Debugger troubleshooting.