Using instrumentation libraries

Go does not support truly automatic instrumentation like other languages today. Instead, you’ll need to depend on instrumentation libraries that generate telemetry data for a particular instrumented library. For example, the instrumentation library for net/hhtp will automatically create spans that track inbound and outbound requests once you configure it in your code.

Setup

Each instrumentation library is a package. In general, this means you need to go get the appropriate package:

go get go.opentelemetry.io/contrib/instrumentation/{import-path}/otel{package-name}

And then configure it in your code based on what the library requires to be activated.

Example with net/http

As an example, here’s how you can set up automatic instrumentation for inbound HTTP requests for net/http:

First, get the net/http instrumentation library:

go get go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp

Next, use the library to wrap an HTTP handler in your code:

package main

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"time"

	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
)

// Package-level tracer.
// This should be configured in your code setup instead of here.
var tracer = otel.Tracer("github.com/full/path/to/mypkg")

// sleepy mocks work that your application does.
func sleepy(ctx context.Context) {
	_, span := tracer.Start(ctx, "sleep")
	defer span.End()

	sleepTime := 1 * time.Second
	time.Sleep(sleepTime)
	span.SetAttributes(attribute.Int("sleep.duration", int(sleepTime)))
}

// httpHandler is an HTTP handler function that is going to be instrumented.
func httpHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Hello, World! I am instrumented autoamtically!")
	ctx := r.Context()
	sleepy(ctx)
}

func main() {
	// Wrap your httpHandler function.
	handler := http.HandlerFunc(httpHandler)
	wrappedHandler := otelhttp.NewHandler(handler, "hello-instrumented")
	http.Handle("/hello-instrumented", wrappedHandler)

	// And start the HTTP serve.
	log.Fatal(http.ListenAndServe(":3030", nil))
}

Assuming that you have a Tracer and exporter configured, this code will:

  • Start an HTTP server on port 3030
  • Automatically generate a span for each inbound HTTP request to /hello-instrumented
  • Create a child span of the automatically-generated one that tracks the work done in sleepy

Connecting manual instrumentation you write in your app with instrumentation generated from a library is essential to get good observability into your apps and services.

Available packages

A full list of instrumentation libraries available can be found in the OpenTelementry registry.

Next steps

Instrumentation libraries can do things like generate telemtry data for inbound and outbound HTTP requests, but they don’t instrument your actual application.

To get richer telemetry data, use manual instrumentatiion to enrich your telemetry data from instrumentation libraries with instrumentation from your running application.