README.md

Resources

Resource Detector

OpenTelemetry .NET SDK provides a resource detector for detecting resource information from the OTEL_RESOURCE_ATTRIBUTES and OTEL_SERVICE_NAME environment variables.

Custom resource detectors can be implemented:

• ResourceDetectors should inherit from OpenTelemetry.Resources.IResourceDetector, (which belongs to the OpenTelemetry package), and implement the Detect method.

A demo ResourceDetector is shown here:

using OpenTelemetry.Resources;

internal class MyResourceDetector : IResourceDetector
{
    public Resource Detect()
    {
        var attributes = new List<KeyValuePair<string, object>>
        {
            new KeyValuePair<string, object>("key", "val"),
        };

        return new Resource(attributes);
    }
}

There are two different ways to add the custom ResourceDetector to the OTEL signals, via the Sdk.Create approach:

using System.Diagnostics;
using System.Diagnostics.Metrics;
using Microsoft.Extensions.Logging;
using OpenTelemetry;
using OpenTelemetry.Metrics;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;

namespace ExtendingTheSdk;

public class Program
{
    private static readonly ActivitySource DemoSource = new("OTel.Demo");
    private static readonly Meter MeterDemoSource = new("OTel.Demo");

    public static void Main()
    {
        using var tracerProvider = Sdk.CreateTracerProviderBuilder()
            .AddSource("OTel.Demo")
            .SetResourceBuilder(ResourceBuilder.CreateEmpty().AddDetector(
                new MyResourceDetector()))
            .Build();

        using var meterProvider = Sdk.CreateMeterProviderBuilder()
            .SetResourceBuilder(ResourceBuilder.CreateEmpty().AddDetector(
                new MyResourceDetector()))
            .Build();

        using var loggerFactory = LoggerFactory.Create(builder =>
        {
            builder.AddOpenTelemetry(options =>
            {
                options.SetResourceBuilder(ResourceBuilder
                    .CreateDefault().AddDetector(
                        new MyResourceDetector()));
            });
        });

        using (var foo = DemoSource.StartActivity("Foo"))
        {
            using (var bar = DemoSource.StartActivity("Bar"))
            {
                using (var baz = DemoSource.StartActivity("Baz"))
                {
                }
            }
        }

        var counter = MeterDemoSource.CreateCounter<long>("counter");
        for (var i = 0; i < 20000; i++)
            counter.Add(1, new("tag1", "value1"), new("tag2", "value2"));

        var logger = loggerFactory.CreateLogger("OTel.Demo");
        logger
            .LogInformation("Hello from {name} {price}.", "tomato", 2.99);
    }
}

or via OpenTelemetry.Extensions.Hosting method:

    services.AddSingleton<MyResourceDetector>();

    services.AddOpenTelemetry()
        .ConfigureResource(builder => builder
            .AddDetector(sp =>
                sp.GetRequiredService<MyResourceDetector>()))
        .WithTracing(builder => builder.AddConsoleExporter())
        .WithMetrics(builder => builder.AddConsoleExporter());