prometheusCore

This is a .NET Core library for instrumenting your applications and exporting metrics to Prometheus.

This library was written to provide full support for dependency injection in .Net Core to reduce overall coding and testing. A BIG thanks to those at Prometheus-net for their library but its usage just wasn't how I wanted to do things.

Installation

Nuget package for general use and metrics export : prometheusCore

Install-Package prometheusCore

Nuget package for ASP.NET Core middleware and metrics api controller: prometheusCore.AspNetCore

Install-Package prometheusCore.AspNet

Nuget package for Hosting in a console service: prometheusCore.AspNetCore

Install-Package prometheusCore.Hosting

Counter Collector

Counters only increase in value and reset to zero when the process restarts.

ICounter counter = new Counter("name", Labels.Empty);
counter.Inc();

Gauge Collector

Gauges can have any numeric value and change arbitrarily.

IGauge gauge = new Gauge("name", Labels.Empty);
gauge.Inc();
gauge.Dec();

Summary Collector

Summaries track the trends in events over time (10 minutes by default).

WIP

Histogram Collector

Histograms track the size and number of events in buckets. This allows for aggregatable calculation of quantiles.

IHistogram histogram = new Histogram("name", Labels.Empty);
histogram.Observe(2);

Labels

All metrics can have labels, allowing grouping of related time series.

See the best practices on naming and labels.

See the Histogram Collector below for an example using a runtime Label value

Injectable Collection of Collectors

You can create an interface/class to be injected into your other objects. This will handle creating each collector for you and add it as a singleton to the IServiceCollection.

public interface ITestCollectors
{
    [CollectorRegistry("got_something_count", "got something count")]
    ICounter GotSomethingCount { get; }
    [CollectorRegistry("got_something_active_count", "actively got something count")]
    IGauge GotSomethingActiveCount { get; }
    [CollectorRegistry("got_something_error_count", "got something error count")]
    ICounter GotSomethingErrorCount { get; }
    [CollectorRegistry("got_something_duration", "go something duration", "user")]
    [HistogramBuckets(.5, 1, 2, 3, 5, 10, 30, 60)]
    ICollectorBuilder<IHistogram> GotSomethingDuration { get; }
}
public class TestCollectors : ITestCollectors
{
    public ICounter GotSomethingCount { get; private set; }
    public IGauge GotSomethingActiveCount { get; private set; }
    public ICounter GotSomethingErrorCount { get; private set; }
    public ICollectorBuilder<ICounter> GotSomethingDuration { get; private set; }

    public HomeCollectors(ICollectorFactory collectorFactory)
    {
        collectorFactory.InjectCollectors<ITestCollectors, TestCollectors>(this);
    }
}
public class TestController
{
    private readonly ITestCollectors _testCollectors;
    public TestController(ITestCollectors testCollectors)
    {
        _testCollectors = testCollectors;
    }

    public IActionResult GetSomething()
    {
        using (var timer = new TimerScope(_testCollectors.GotSomethingDuration.WithLabels(HttpContext.User.ToString)))
        {
            try
            {
                _testCollectors.GotSomethingActiveCount.Inc();
                GoGetSomething();
                _testCollectors.GotSomethingCount.Inc();
            }
            catch(Exception)
            {
                _testCollectors.GotSomethingErrorCount.Inc();
            }
            finally
            {
                _testCollectors.GotSomethingActiveCount.Dec();
            }
        }
    }
}
public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddPrometheus()
                .Register<ITestCollectors, TestCollectors>()
                .Build();
    }
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        app.UsePrometheus();
        app.UseMvc();
    }
}

ASP.NET Core exporter middleware

For projects built with ASP.NET Core, a middleware plugin is provided.

If you use the default Visual Studio project template, modify Startup.cs as follows:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UsePrometheus();
    app.UseMvc();
}

The default configuration will publish metrics on the /metrics URL.

This functionality is delivered in the prometheusCore.AspNet NuGet package.