Azure Function Serilog Not Writing to App Insights

Question

I am trying to get my function to log to app insights but I seem to have tried several things and to no avail. I am using V4 functions and running it locally using

var config = TelemetryConfiguration.Active;
var logger = new LoggerConfiguration()
    .MinimumLevel.Debug()
    .Enrich.FromLogContext()
    .WriteTo.ApplicationInsights(config, TelemetryConverter.Traces)
    .CreateLogger();

Please note I am aware TelemetryConfiguration.Active is not recommended but I am trying to get something to work for now.

The host is setup as:

var host = new HostBuilder()
    .UseSerilog((context, configuration) =>
    {
        configuration.Enrich.FromLogContext();
    })
    .ConfigureFunctionsWorkerDefaults()
    .ConfigureServices((hostContext, services) =>
    {
        services.AddLogging(logging => logging.AddSerilog(logger, true));
    })
    .Build();

host.Run();

My appsettings has instrumentation key set

{
  "ApplicationInsights": {
    "InstrumentationKey": "59d7227e-",
    "EnableAdaptiveSampling": false,
    "EnablePerformanceCounterCollectionModule": false
  }
}

My function I attempt to use ILogger to do the following

            _logger.LogInformation("HELLO WORLD");
            _logger.LogWarning("HELLO WORLD WARNING");

However I don't see these log lines in app insights. What am I doing wrong here?

Answer 1

To write logs below Warning level to Application Insights you need to add following code to Program.cs in .NET 8:

services.Configure<LoggerFilterOptions>(options =>
{
    LoggerFilterRule toRemove = options.Rules.FirstOrDefault(rule => rule.ProviderName
        == "Microsoft.Extensions.Logging.ApplicationInsights.ApplicationInsightsLoggerProvider");

    if (toRemove is not null)
    {
        options.Rules.Remove(toRemove);
    }
});

For Serilog: I am writing to console and sending it to Application Insights

services.AddLogging(logbuilder =>
{
    logbuilder.AddSerilog(new LoggerConfiguration()
        .WriteTo.Console()
        .CreateLogger());
});

If you want to add minimun loglevel you can use

logbuilder.AddSerilog(new LoggerConfiguration()
        .MinimumLevel.Debug()
        .WriteTo.Console()
        .CreateLogger());

My Code:

Function1.cs:

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;


namespace FunctionApp2
{
    public class Function1
    {
        private readonly ILogger<Function1> _logger;

        public Function1(ILogger<Function1> logger)
        {
            _logger = logger;
        }

        [Function("Function1")]
        public IActionResult Run([HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequest req)
        {
            _logger.LogInformation("C# HTTP trigger function processed a request.");
            return new OkObjectResult("Welcome to Azure Functions!");
        }
    }
}

Program.cs:

using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Serilog;

var host = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureServices(services =>
    {
        services.AddApplicationInsightsTelemetryWorkerService();
        services.ConfigureFunctionsApplicationInsights();
        services.Configure<LoggerFilterOptions>(options =>
        {
            LoggerFilterRule toRemove = options.Rules.FirstOrDefault(rule => rule.ProviderName
                == "Microsoft.Extensions.Logging.ApplicationInsights.ApplicationInsightsLoggerProvider");

            if (toRemove is not null)
            {
                options.Rules.Remove(toRemove);
            }
        });
        services.AddLogging(logbuilder =>
        {
            logbuilder.AddSerilog(new LoggerConfiguration()
                .WriteTo.Console()
                .CreateLogger()); ;
        });
    })
    .Build();

host.Run();

.csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <OutputType>Exe</OutputType>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.20.1" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.1.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="1.2.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.16.4" />
    <PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.21.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="1.1.0" />
    <PackageReference Include="Serilog" Version="3.1.1" />
    <PackageReference Include="Serilog.Extensions.Logging" Version="8.0.0" />
    <PackageReference Include="Serilog.Sinks.Console" Version="5.0.1" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
  <ItemGroup>
    <Using Include="System.Threading.ExecutionContext" Alias="ExecutionContext" />
  </ItemGroup>
</Project>

OUTPUT:

Local:

Azure Application Insights: