Issues with OpenTelemetry Integration in .NET 8 Azure Function App

I have developed a .NET 8 Function App using the isolated worker model. Following the guidelines provided in the Microsoft documentation : https://learn.microsoft.com/en-us/azure/azure-functions/opentelemetry-howto?tabs=app-insights&pivots=programming-language-csharp, I have integrated OpenTelemetry with Azure Functions.

Below are the details of my implementation:

host.json:

{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": true,
        "maxTelemetryItemsPerSecond": 20,
        "excludedTypes": "Request;Exception"
      },
      "enableLiveMetrics": true
    },
    "logLevel": {
      "default": "Information",
      "Function": "Information",
      "Host.Aggregator": "Trace",
      "Host.Results": "Information"
    }
  },
  "telemetryMode": "openTelemetry",
  "retry": {
    "strategy": "fixedDelay",
    "maxRetryCount": 1,
    "delayInterval": "00:00:04"
  },
  "extensions": {
    "queues": {
      "maxPollingInterval": "00:00:00.200",
      "visibilityTimeout": "00:00:30",
      "batchSize": 16,
      "maxDequeueCount": 200,
      "newBatchThreshold": 8
    }
  }
}

Project file:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <OutputType>Exe</OutputType>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <Content Include="local.settings.json">
      <CopyToOutputDirectory>Never</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </Content>
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Azure.Extensions.AspNetCore.Configuration.Secrets" />
    <PackageReference Include="Azure.Monitor.OpenTelemetry.AspNetCore" />
    <PackageReference Include="Microsoft.Azure.Functions.Extensions" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.DurableTask" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Storage.Blobs" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Storage.Queues" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.OpenTelemetry" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" />
    <PackageReference Include="Microsoft.Data.SqlClient" />
    <PackageReference Include="Microsoft.Extensions.Configuration.UserSecrets" />
    <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
    <PackageReference Include="OpenTelemetry.Extensions.Hosting" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
  </ItemGroup>
  <ItemGroup>
    <Using Include="System.Threading.ExecutionContext" Alias="ExecutionContext" />
  </ItemGroup>
</Project>

private static void ConfigureOpenTelemetry(IServiceCollection services, IConfiguration config, string appName)
{
    // Binds configuration to AppCloudServiceOptions and validates it
    // Returns the validated configuration object
    var appConfig = services.BindValidateReturn<AppCloudServiceOptions>(config);

    // Configures logging services with OpenTelemetry
    services.AddLogging(loggingBuilder =>
    {
        // Removes any existing logging providers
        loggingBuilder.ClearProviders();

        // Adds OpenTelemetry logging provider with specific configuration
        loggingBuilder.AddOpenTelemetry(logging =>
        {
            // Enables including formatted log messages in telemetry
            logging.IncludeFormattedMessage = true;

            // Enables logging scopes to maintain context across log entries
            logging.IncludeScopes = true;

        });
    });

    // Adds OpenTelemetry services and configures Azure Monitor as the telemetry backend
    services.AddOpenTelemetry().UseFunctionsWorkerDefaults().UseAzureMonitor();

    // Configures OpenTelemetry with Application Insights connection string and application name
    // This enables sending telemetry data to Azure Application Insights
    services.AddOpenTelemetry(appConfig.AppInsightsConnString, appName);
}

internal static OpenTelemetryBuilder AddOpenTelemetry(this IServiceCollection services, string appInsightsConnString, string appName) =>
services.AddOpenTelemetry().UseAzureMonitor(options =>
{
    options.ConnectionString = appInsightsConnString;
})
    .ConfigureResource(resource => resource.AddService(appName))
    .WithTracing(tracing => tracing
        .AddAspNetCoreInstrumentation()
        .AddHttpClientInstrumentation()
        .AddEntityFrameworkCoreInstrumentation()
        .AddRedisInstrumentation()
    .AddAzureMonitorTraceExporter(options => options.ConnectionString = appInsightsConnString))
    .WithMetrics(metrics => metrics
        .AddAspNetCoreInstrumentation()
        .AddHttpClientInstrumentation()
        .AddRuntimeInstrumentation()
    .AddAzureMonitorMetricExporter(options => options.ConnectionString = appInsightsConnString));

I deployed the above application in one DEV environment and did some validation. On validation I found that no requests are getting logged for the functionapp case. I only see entries of itemType: trace, dependency, exception. Also all the trace, dependency, exception does not have operation_Name column. On the other hand when I try to compare these with API, I see entries of itemType : request, trace, dependency, exception including the operation_Name column.

Could anyone please help me understand the reasons for the issues I am encountering with this setup?

I am able to send traces to Application insights using below code:

host.json:

{
  "version": "2.0",
  "telemetryMode": "openTelemetry",
  "logging": {
    "applicationInsights": {
      "enableLiveMetrics": true,
      "samplingSettings": {
        "isEnabled": true,
        "maxTelemetryItemsPerSecond": 20,
        "excludedTypes": "Request;Exception"
      }
    },
    "logLevel": {
      "default": "Information",
      "Function": "Information",
      "Host.Aggregator": "Trace",
      "Host.Results": "Information"
    }
  }
}

local.settings.json:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "TestRith__testconstring": "InstrumentationKey=rithwik;IngestionEndpoint=https://eastus-8.in.applicationinsights.azure.com/;LiveEndpoint=https://eastus.livediagnostics.monitor.azure.com/;ApplicationId=cfrithwik35"
  }
  }

Program.cs:

using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;
using OpenTelemetry.Metrics;
using Azure.Monitor.OpenTelemetry.Exporter;
using FunctionApp12;

var ri_hst = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureAppConfiguration(config =>
    {
        config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
              .AddEnvironmentVariables();
    })
    .ConfigureServices((context, services) =>
    {
        var config = context.Configuration;
        var rithConf = new RithServiceCldOps();
        config.Bind("TestRith", rithConf);

        string riappnme = "RithwikFunctionApp";
        services.AddOpenTelemetry()
            .ConfigureResource(resource => resource.AddService(riappnme))
            .WithTracing(b =>
            {
                b.AddHttpClientInstrumentation()
                 .AddAzureMonitorTraceExporter(o =>
                 {
                     o.ConnectionString = rithConf.testconstring;
                 });
            })
            .WithMetrics(b =>
            {
                b.AddHttpClientInstrumentation()
                 .AddRuntimeInstrumentation()
                 .AddAzureMonitorMetricExporter(o =>
                 {
                     o.ConnectionString = rithConf.testconstring;
                 });
            });
        services.AddLogging(loggingBuilder =>
        {
            loggingBuilder.ClearProviders();
            loggingBuilder.AddOpenTelemetry(tstlgr =>
            {
                tstlgr.IncludeFormattedMessage = true;
                tstlgr.IncludeScopes = true;
                tstlgr.ParseStateValues = true;
                tstlgr.AddAzureMonitorLogExporter(o =>
                {
                    o.ConnectionString = rithConf.testconstring;
                });
            });
        });
    })
    .Build();

ri_hst.Run();

namespace FunctionApp12
{
    public class RithServiceCldOps
    {
        public string testconstring { get; set; } = string.Empty;
    }
}

Function.cs:

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

namespace FunctionApp12
{
    public class Function1
    {
        private readonly ILogger<Function1> rilg;
        public Function1(ILogger<Function1> lg)
        {
            rilg = lg;
        }
        [Function("Function1")]
        public IActionResult Run([HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequest req)
        {
            rilg.LogInformation("Rithwik Test info");
            rilg.LogError("Rithwik Test error");
            rilg.LogCritical("Rithwik Test critical");
            rilg.LogWarning("Rithwik Test warning");
            return new OkObjectResult("Test Rithwik!");
        }
    }
}

Output:

Application Insights Logs:

Here, I have used Http trigger, you can use your trigger.

Edit:

using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;
using OpenTelemetry.Metrics;
using Azure.Monitor.OpenTelemetry.Exporter;
using FunctionApp12;

var chohost = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureAppConfiguration(config =>
    {
        config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
              .AddEnvironmentVariables();
    })
    .ConfigureServices((context, services) =>
    {
        var config = context.Configuration;
        var chcnfg = new RithServiceCldOps();
        config.Bind("TestRith", chcnfg);

        string riappnme = "TestRIthwik";

        services.AddOpenTelemetry()
            .ConfigureResource(resource => resource.AddService(riappnme))
            .WithTracing(b =>
            {
                b.AddSource("Microsoft.Azure.Functions.Worker") 
                 .AddHttpClientInstrumentation()
                 .AddAzureMonitorTraceExporter(o =>
                 {
                     o.ConnectionString = chcnfg.testconstring;
                 });
            })
            .WithMetrics(b =>
            {
                b.AddHttpClientInstrumentation()
                 .AddRuntimeInstrumentation()
                 .AddAzureMonitorMetricExporter(o =>
                 {
                     o.ConnectionString = chcnfg.testconstring;
                 });
            });

        services.AddLogging(loggingBuilder =>
        {
            loggingBuilder.ClearProviders();
            loggingBuilder.AddOpenTelemetry(rilgr =>
            {
                rilgr.IncludeFormattedMessage = true;
                rilgr.IncludeScopes = true;
                rilgr.ParseStateValues = true;
                rilgr.AddAzureMonitorLogExporter(o =>
                {
                    o.ConnectionString = chcnfg.testconstring;
                });
            });
        });
    })
    .Build();

chohost.Run();

namespace FunctionApp12
{
    public class RithServiceCldOps
    {
        public string testconstring { get; set; } = string.Empty;
    }
}

Output: