Getting started with metrics - ASP.NET Core

Learn how to use OpenTelemetry Metrics in an ASP.NET Core application

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This guide will show you how to get started with OpenTelemetry .NET Metrics in an ASP.NET Core application in just a few minutes.

Prerequisites

Creating an ASP.NET Core application

Create a new ASP.NET Core web application:

dotnet new web -o aspnetcoreapp
cd aspnetcoreapp

Adding OpenTelemetry metrics

Install the required OpenTelemetry packages:

dotnet add package OpenTelemetry.Exporter.Console
dotnet add package OpenTelemetry.Extensions.Hosting
dotnet add package OpenTelemetry.Instrumentation.AspNetCore

Update the Program.cs file with the following code:

using OpenTelemetry.Metrics;
using OpenTelemetry.Resources;

var builder = WebApplication.CreateBuilder(args);

// Configure OpenTelemetry with metrics and auto-start.
builder.Services.AddOpenTelemetry()
    .ConfigureResource(resource => resource
        .AddService(serviceName: builder.Environment.ApplicationName))
    .WithMetrics(metrics => metrics
        .AddAspNetCoreInstrumentation()
        .AddConsoleExporter((exporterOptions, metricReaderOptions) =>
        {
            metricReaderOptions.PeriodicExportingMetricReaderOptions.ExportIntervalMilliseconds = 1000;
        }));

var app = builder.Build();

app.MapGet("/", () => $"Hello from OpenTelemetry Metrics!");

app.Run();

Running the application

Run the application:

dotnet run

Browse to the URL shown in the console (for example, http://localhost:5000).

You should see metrics output in the console similar to:

Export http.server.duration, Measures the duration of inbound HTTP requests., Unit: ms, Meter: OpenTelemetry.Instrumentation.AspNetCore/1.0.0.0
(2023-04-11T21:49:43.6915232Z, 2023-04-11T21:50:50.6564690Z) http.flavor: 1.1 http.method: GET http.route: / http.scheme: http http.status_code: 200 net.host.name: localhost net.host.port: 5000 Histogram
Value: Sum: 3.5967 Count: 11 Min: 0.073 Max: 2.5539
(-Infinity,0]:0
(0,5]:11
(5,10]:0
(10,25]:0
(25,50]:0
(50,75]:0
(75,100]:0
(100,250]:0
(250,500]:0
(500,750]:0
(750,1000]:0
(1000,2500]:0
(2500,5000]:0
(5000,7500]:0
(7500,10000]:0
(10000,+Infinity]:0

Congratulations! You are now collecting metrics from your ASP.NET Core application using OpenTelemetry.

How it works

OpenTelemetry registration

The application registers OpenTelemetry services using the dependency injection container provided by ASP.NET Core:

builder.Services.AddOpenTelemetry()
    .ConfigureResource(resource => resource
        .AddService(serviceName: builder.Environment.ApplicationName))
    .WithMetrics(metrics => metrics
        .