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This guide will help you instrument the net/http stack of your Go application(s) with OpenTelemetry and send traces to Checkly.

Step 1: Install the OpenTelemetry SDK

Install the relevant OpenTelemetry packages:

go get "go.opentelemetry.io/otel" \
  "go.opentelemetry.io/otel/propagation" \
  "go.opentelemetry.io/otel/sdk/trace" \
  "go.opentelemetry.io/otel/exporters/otlp/otlptrace" \
  "go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp" \
  "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"

Step 2: Set up SDK

Create a file called tracing.go at the root of your project and add the following code:

// tracing.go

package main

import (
	"context"
	"errors"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/trace"
)

func setupOTelSDK(ctx context.Context) (shutdown func(context.Context) error, err error) {
	var shutdownFuncs []func(context.Context) error

	shutdown = func(ctx context.Context) error {
		var err error
		for _, fn := range shutdownFuncs {
			err = errors.Join(err, fn(ctx))
		}
		shutdownFuncs = nil
		return err
	}

	handleErr := func(inErr error) {
		err = errors.Join(inErr, shutdown(ctx))
	}

	prop := newPropagator()
	otel.SetTextMapPropagator(prop)

	tracerProvider, err := newTraceProvider()
	if err != nil {
		handleErr(err)
		return
	}
	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
	otel.SetTracerProvider(tracerProvider)

	return
}

func newPropagator() propagation.TextMapPropagator {
	return propagation.NewCompositeTextMapPropagator(
		propagation.TraceContext{},
		propagation.Baggage{},
	)
}

func newTraceProvider() (*trace.TracerProvider, error) {

	traceClient := otlptracehttp.NewClient()

	var traceExporter, err = otlptrace.New(context.Background(), traceClient)
	if err != nil {
		return nil, err
	}

	bsp := trace.NewBatchSpanProcessor(traceExporter)

	tracerProvider := trace.NewTracerProvider(
		trace.WithSampler(trace.AlwaysSample()),
		trace.WithSpanProcessor(bsp),
	)

	return tracerProvider, nil
}

Step 3: Initialize the instrumentation

Add or adapt the following code to your main.go file. The key parts are as follows:

  1. Wrap the default http.Handler with theotelhttp.NewHandler function.
  2. Add the otelChecklyFilter function to filter out the requests that should be traced and send to Checkly.
// main.go

package main

import (
	"context"
	"errors"
	"log"
	"net"
	"net/http"
	"os"
	"os/signal"
	"strings"

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

func main() {
	if err := run(); err != nil {
		log.Fatalln(err)
	}
}

func run() (err error) {
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
	defer stop()

	otelShutdown, err := setupOTelSDK(ctx)
	if err != nil {
		return
	}

	defer func() {
		err = otelShutdown(context.Background())
	}()

	handler := http.Handler(http.DefaultServeMux)
	wrappedHandler := otelhttp.NewHandler(handler, "", otelhttp.WithFilter(otelChecklyFilter))

	srv := &http.Server{
		Addr:        ":8080",
		BaseContext: func(_ net.Listener) context.Context { return ctx },
		Handler:     wrappedHandler,
	}
	srvErr := make(chan error, 1)
	go func() {
		srvErr <- srv.ListenAndServe()
	}()

	select {
	case err = <-srvErr:
		return
	case <-ctx.Done():
		stop()
	}

	err = srv.Shutdown(context.Background())
	return
}

func otelChecklyFilter(req *http.Request) bool {
	header := req.Header.Get("tracestate")
	return header != "" && strings.Contains(header, "checkly=true")
}

Step 4: Start your app with the instrumentation

First, toggle on Send Traces, grab your OTel API key in the OTel API keys section of the Open Telemetry Integration page in the Checkly app and take a note of the endpoint for the region you want to use.

Checkly OTEL API keys

Now, export your API key in your shell by setting the OTEL_EXPORTER_OTLP_HEADERS environment variable.

export OTEL_EXPORTER_OTLP_HEADERS="authorization=<your-api-key>"

Next, export the endpoint for the region you want to use and give your service a name.

export OTEL_EXPORTER_OTLP_ENDPOINT="https://otel.eu-west-1.checklyhq.com"
export OTEL_SERVICE_NAME="your-service-name"
During the beta we only have one region available: eu-west-1. We will expand to US regions soon.

We are using the standard OpenTelemetry environment variables here to configure the OTLP exporter.

Variable Description
OTEL_EXPORTER_OTLP_HEADERS The Authorization HTTP header containing your Checkly OTel API key.
OTEL_EXPORTER_OTLP_ENDPOINT The Checkly OTel API endpoint for the region you want to use.
OTEL_SERVICE_NAME The name of your service to identify it among the spans in the web UI.

Then run you app as usual:

go run .
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Last updated on July 29, 2024. You can contribute to this documentation by editing this page on Github