Monitoring C# (.NET) Applications with AppMetrics

AppMetrics Library for Monitoring C# (.NET) Applications

When developing modern .NET applications, it is critically important to track their state, performance, and identify bottlenecks. The AppMetrics library is a powerful and flexible tool for collecting, aggregating, and exporting metrics in real time. It allows developers and administrators to get a complete picture of the service's operation: from request execution time to error frequency.

AppMetrics supports many backends for storing metrics: Prometheus, InfluxDB, Graphite, Elasticsearch, and others. Thanks to built-in Health Checks, you can not only collect statistics but also check the health of dependencies (databases, external APIs).

Key Features

• Counters — number of requests, errors, events.
• Histograms — distribution of operation execution time.
• Timers — measuring code execution duration.
• Meters — rate of events per second.
• Health Checks — checking the availability of external services.
• Metrics Export — to Prometheus (/metrics format), InfluxDB, and others.

Installation and Setup

Install the package via NuGet:

dotnet add package AppMetrics.AspNetCore.Mvcdotnet add package AppMetrics.Reporting.Prometheus.Client

Then add services in Program.cs (or Startup.cs):

using App.Metrics;using App.Metrics.AspNetCore;using App.Metrics.Formatters.Prometheus;

var builder = WebApplication.CreateBuilder(args);

// Metrics configurationvar metrics = AppMetrics.CreateDefaultBuilder()    .OutputMetrics.AsPrometheusPlainText()    .Build();

builder.Services.AddMetrics(metrics);builder.Services.AddMetricsTrackingMiddleware();builder.Services.AddMetricsEndpoints();

var app = builder.Build();

app.UseMetricsAllMiddleware();app.UseMetricsAllEndpoints();

app.MapGet("/", () => "Hello World!");

app.Run();

After starting the application, metrics will be available at /metrics in Prometheus format.

Creating Custom Metrics

Define a class for storing metrics:

public class MyMetrics{    private readonly IMetrics _metrics;

    public MyMetrics(IMetrics metrics)    {        _metrics = metrics;    }

    // Request counter    private readonly CounterOptions _requestCounter = new CounterOptions    {        Name = "myapp_requests_total",        MeasurementUnit = Unit.Requests    };

    // Timer for measuring execution time    private readonly TimerOptions _requestTimer = new TimerOptions    {        Name = "myapp_request_duration_seconds",        MeasurementUnit = Unit.Requests,        DurationUnit = TimeUnit.Seconds    };

    public void TrackRequest()    {        _metrics.Measure.Counter.Increment(_requestCounter);    }

    public IDisposable MeasureRequestDuration()    {        return _metrics.Measure.Timer.Time(_requestTimer);    }}

Use metrics in controllers:

[ApiController][Route("api/[controller]")]public class SampleController : ControllerBase{    private readonly MyMetrics _myMetrics;

    public SampleController(MyMetrics myMetrics)    {        _myMetrics = myMetrics;    }

    [HttpGet]    public IActionResult Get()    {        _myMetrics.TrackRequest();

        using (_myMetrics.MeasureRequestDuration())        {            // Simulating work            Thread.Sleep(100);        }

        return Ok("Metrics tracked");    }}

Health Checks