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Nexogen.Libraries.Metrics

Library for collecting application metrics in .Net and exporting them to Prometheus

API Reference

Nexogen.Libraries.Metrics API Reference

Updating from version 2.6.0 or earlier

The default Prometheus metrics registration behavior in ASP.NET Core applications has changed. The request metrics collection is no longer enabled by default. This means that you need to add code to enable it. See the relevant section below for code samples. Explicitly defined metrics are not affected in any way.

Installation

dotnet add package Nexogen.Libraries.Metrics.Prometheus
dotnet add package Nexogen.Libraries.Metrics.Extensions

You can use an interface only nuget when writing libraries or when you want to use Metrics through dependency injection.

dotnet add package Nexogen.Libraries.Metrics

For exporting metrics you currently have to use ASP.NET Core.

dotnet add package Nexogen.Libraries.Metrics.Prometheus.AspCore

Or you can use a push gateway when measuring batch processes.

dotnet add package Nexogen.Libraries.Metrics.Prometheus.PushGateway

Example usage - Measurements

Counters

Counters can only increment, so they are most useful for counting things, like calls to API endpoints or backend services.

IMetrics metrics = new PrometheusMetrics();

ICounter counter = metrics.Counter()
    .Name("nexogen_sort_calls_total")
    .Help("Total calls to sort routine.")
    .Register();

counter.Increment();

Gauges

Gauges can take any value, so they are the most versatile metric type available. You can even measure durations or dates with them!

IGauge gauge = metrics.Gauge()
    .Name("nexogen_sorted_items_count_last")
    .Help("The last count of the sorted items.")
    .Register();

gauge.Value = items.Length;

gauge.Increment();
gauge.Decrement(10.1);           

Histograms

Histograms are a trade off between measuring resolution and precision. With histograms you can avoid aliasing errors from Prometheus's scrape interval, but lose granularity. Histograms also need to have their buckets defined before use and we provide sevaral bucket generators to make it easy.

IHistogram histogram = metrics.Histogram()
    .LinearBuckets(0.01, 0.01, 100)
    .Name("nexogen_sort_time_seconds")
    .Help("Time taken for sort in seconds.")
    .Register();

var sw = Stopwatch.StartNew();
Array.Sort(items);
histogram.Observe(sw.Elapsed.TotalSeconds);

Extensions

We provide an Extensions library for making common measurements easy.

using (histogram.Timer())
{
    Array.Sort(items);
}

gauge.SetToCurrentTime();

gauge.TrackInProgress(() => Array.Sort(items));

ASP.NET Core metrics collection

There is a way to automatically collect metrics about the ASP.NET Core requests. This needs to be enabled when registering to the application.

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UsePrometheus(options => options.CollectHttpMetrics());
}

The options.CollectHttpMetrics() registers automatic request metric collection, which was implicitly registered in versions prior to version 3.0.0.

Example usage - Exposing metrics

Asp.Net Core

The collected metrics can be exposed via ASP.NET Core middleware. To do this you need to register the feature during configuration.

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

Standalone server

There is a standalone server if you don't want to use ASP.NET Core just to expose your metrics.

dotnet add package Nexogen.Libraries.Metrics.Prometheus.Standalone

public void ConfigureServices(IServiceCollection services)
{
    services.AddPrometheusStandalone(Configuration.GetSection("Prometheus"));
}

or

var metrics = new PrometheusMetrics();
await new PrometheusServer(new PrometheusServerOptions {Port = 9100}, metrics, loggerFactory).StartAsync();

gRPC

We provide gRPC interceptors for capturing metrics.

dotnet add package Nexogen.Libraries.Metrics.Prometheus.Grpc

For gRPC servers:

services.AddSingleton<IGrpcServerMetrics, GrpcServerMetrics>()
        .AddGrpc(options => options.Interceptors.Add<ServerMetricsInterceptor>());

For gRPC clients:

services.AddSingleton<IGrpcClientMetrics, GrpcClientMetrics>()
        .AddGrpcClient<T>((provider, options) => options.Interceptors.Add(new ClientMetricsInterceptor(provider.GetRequiredService<IGrpcClientMetrics>())));