Automatic Instrumentation

.NET supports automatic instrumentation with instrumentation libraries that generate telemetry data for a particular instrumented library.

For example, the instrumentation library for ASP.NET Core will automatically create spans that track inbound requests once you configure it in your app/service.

Setup

Each instrumentation library is a NuGet package, and installing them is typically done like so:

dotnet add package OpenTelemetry.Instrumentation.{library-name-or-type}

It is typically then registered at application startup time, such as when creating a TracerProvider.

Example with ASP.NET Core and HttpClient

As an example, here’s how you can automatically instrument inbound and output requests from an ASP.NET Core app.

First, get the appropriate packages:

dotnet add package OpenTelemetry --prerelease
dotnet add package OpenTelemetry.Extensions.Hosting --prerelease
dotnet add package OpenTelemetry.Exporter.Console --prerelease
dotnet add package OpenTelemetry.Instrumentation.AspNetCore --prerelease
dotnet add package OpenTelemetry.Instrumentation.Http --prerelease

Next, configure each instrumentation library at startup and use them!

using System.Diagnostics;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;

// Define some important constants and the activity source
var serviceName = "MyCompany.MyProduct.MyService";
var serviceVersion = "1.0.0";

var builder = WebApplication.CreateBuilder(args);

// Configure important OpenTelemetry settings, the console exporter, and automatic instrumentation
builder.Services.AddOpenTelemetryTracing(b =>
{
    b
    .AddConsoleExporter()
    .AddSource(serviceName)
    .SetResourceBuilder(
        ResourceBuilder.CreateDefault()
            .AddService(serviceName: serviceName, serviceVersion: serviceVersion))
    .AddHttpClientInstrumentation()
    .AddAspNetCoreInstrumentation();
});

var app = builder.Build();

var httpClient = new HttpClient();

app.MapGet("/hello", async () =>
{
    var html = await httpClient.GetStringAsync("https://example.com/");
    if (string.IsNullOrWhiteSpace(html))
    {
        return "Hello, World!";
    }
    else
    {
        return "Hello, World!";
    }
});

app.Run();

When you run this code and access the /hello endpoint, it will:

• Start a new trace
• Automatically generate a span representing the request made to the endpoint
• Automatically generate a child span representing the HTTP GET made to https://example.com/

If you add more instrumentation libraries, then you can generate more data automatically.

Available instrumentation libraries

A full list of instrumentation libraries produced by OpenTelemetry is available in the opentelemetry-dotnet repository.

You can also find more instrumentations available in the opentelemetry registry.

Next steps

After you have set up instrumentation libraries, you may want to add manual instrumentation to collect custom telemetry data.

If you are using .NET Framework 4.x instead of modern .NET, refer to the .NET Framework docs to configure OpenTelemetry and instrumentation libraries on .NET Framework.

You’ll also want to configure an appropriate exporter to export your telemetry data to one or more telemetry backends.