Example go otel server

otel.go

// Copyright The OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

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

	"github.com/gorilla/mux"

	"go.opentelemetry.io/contrib/instrumentation/github.com/gorilla/mux/otelmux"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/otlp"
	"go.opentelemetry.io/otel/exporters/otlp/otlpgrpc"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	oteltrace "go.opentelemetry.io/otel/trace"
)

var tracer = otel.Tracer("mux-server")

func main() {
	tp := initTracer()
	defer func() {
		if err := tp.Shutdown(context.Background()); err != nil {
			log.Printf("Error shutting down tracer provider: %v", err)
		}
	}()
	r := mux.NewRouter()
	r.Use(otelmux.Middleware("my-server"))
	r.HandleFunc("/users/{id:[0-9]+}", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		vars := mux.Vars(r)
		id := vars["id"]
		name := getUser(r.Context(), id)
		reply := fmt.Sprintf("user %s (id %s)\n", name, id)
		_, _ = w.Write(([]byte)(reply))
	}))
	http.Handle("/", r)
	_ = http.ListenAndServe(":8080", nil)
}

func initTracer() *sdktrace.TracerProvider {
	ctx := context.Background()

	// Create the OTLP exporter that
	// will receive the telemetry data
	endpoint := os.Getenv("EXPORTER_ENDPOINT")
	if endpoint == "" {
		// endpoint = "localhost:55680"
		endpoint = "localhost:8200"
	}
	driver := otlpgrpc.NewDriver(
		otlpgrpc.WithInsecure(),
		otlpgrpc.WithEndpoint(endpoint),
	)
	exporter, err := otlp.NewExporter(ctx, driver)
	if err != nil {
		log.Fatal(err)
	}
	ary := attribute.Array("unhandled_ids", []string{"123", "456"})
	resources := resource.NewWithAttributes(ary)
	tp := sdktrace.NewTracerProvider(
		sdktrace.WithSampler(sdktrace.AlwaysSample()),
		sdktrace.WithBatcher(exporter),
		sdktrace.WithResource(resources),
	)
	otel.SetTracerProvider(tp)
	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}))
	return tp
}

func getUser(ctx context.Context, id string) string {
	ary := attribute.Array("other_ids", []string{"778", "097"})
	_, span := tracer.Start(ctx, "getUser", oteltrace.WithAttributes(ary))
	// _, span := tracer.Start(ctx, "getUser", oteltrace.WithAttributes(attribute.String("some_new_label", id)))
	defer span.End()
	if id == "123" {
		return "otelmux tester"
	}
	return "unknown"
}