inanzzz | OpenTelemetry HTTP client server example with Golang

This example demonstrates how you can attach OpenTelemetry tracing to outgoing HTTP client request and server response. As this is a follow up to the previous example linked below I am cutting it short.

Config

This piece of code is just an addition to http.go file you can find in the previous post - Implementing OpenTelemetry and Jaeger tracing in Golang HTTP API.

// HTTPClientTransporter is a convenience function which helps attaching tracing
// functionality to conventional HTTP clients.
func HTTPClientTransporter(rt http.RoundTripper) http.RoundTripper {
	return otelhttp.NewTransport(rt)
}

Client

This is just an example so you are meant to tidy it up. It is calling the server and expecting a response.

package service

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

	"github.com/you/client/internal/pkg/trace"
)

type service struct {
	// ...
}

func (s service) httpRequest(ctx context.Context) error {
	// Create a child span.
	ctx, span := trace.NewSpan(ctx, "service.httpRequest", nil)
	defer span.End()

	ctx, cancel := context.WithTimeout(ctx, time.Second*10)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://localhost:8090/server/users", nil)
	if err != nil {
		trace.AddSpanError(span, err)
		trace.FailSpan(span, "request error")

		return err
	}

	res, err := trace.HTTPClientTransporter(http.DefaultTransport).RoundTrip(req)
	defer res.Body.Close()
	if err != nil {
		trace.AddSpanError(span, err)
		trace.FailSpan(span, "rounttrip error")

		return err
	}

	if res.StatusCode != http.StatusOK {
		err := fmt.Errorf("unexpected response code")

		trace.AddSpanError(span, err)
		trace.FailSpan(span, "response error")

		return err
	}

	return nil
}

Server

Same as above, you can tidy this up as well.

// ...

func main() {
	ctx := context.Background()

	// Bootstrap tracer.
	prv, err := trace.NewProvider(trace.ProviderConfig{
		JaegerEndpoint: "http://localhost:14268/api/traces",
		ServiceName:    "server",
		ServiceVersion: "2.0.0",
		Environment:    "dev",
		Disabled:       false,
	})
	if err != nil {
		log.Fatalln(err)
	}
	defer prv.Close(ctx)

	handler := http.NewServeMux()
	handler.HandleFunc("/server/users", trace.HTTPHandlerFunc(app.User{}.Create, "users_create"))

	log.Fatal(http.ListenAndServe(":8090", handler))
}

// ...

func (u User) Create(w http.ResponseWriter, r *http.Request) {
	// Create the parent span.
	_, span := trace.NewSpan(r.Context(), "User.Create", nil)
	defer span.End()

	// ...
}

Result

The first three are a successful request and the last two is failed tracing information.