[net/http] enhance otelhttp example to support metric

Signed-off-by: Ziqi Zhao <zhaoziqi9146@gmail.com>

CHANGELOG.md

@@ -79,6 +79,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Add gRPC trace `Filter` to the `go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc` package to provide the way to filter the traces automatically generated in interceptors. (#2572)
 - The `TextMapPropagator` function to `go.opentelemetry.io/contrib/propagators/autoprop`.
   This function is used to return a composite `TextMapPropagator` from registered names (instead of having to specify with an environment variable). (#2593)
+- Enhance otelhttp example to support metric. (#2610)
 
 ### Changed
 

instrumentation/net/http/otelhttp/example/README.md

@@ -8,7 +8,7 @@ Bring up the `http-server` and `http-client` services to run the example:
 docker-compose up --detach http-server http-client
 ```
 
-The `http-client` service sends just one HTTP request to `http-server` and then exits. View the span generated to `stdout` in the logs:
+The `http-client` service sends just one HTTP request to `http-server` and then exits. View the span and metric generated to `stdout` in the logs:
 ```sh
 docker-compose logs http-client
 ```

instrumentation/net/http/otelhttp/example/go.mod

@@ -7,8 +7,10 @@ replace go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp => ../
 require (
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.36.4
 	go.opentelemetry.io/otel v1.11.1
+	go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v0.33.0
 	go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.11.1
 	go.opentelemetry.io/otel/sdk v1.11.1
+	go.opentelemetry.io/otel/sdk/metric v0.33.0
 	go.opentelemetry.io/otel/trace v1.11.1
 )
 

instrumentation/net/http/otelhttp/example/go.sum

@@ -11,12 +11,16 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
 go.opentelemetry.io/otel v1.11.1 h1:4WLLAmcfkmDk2ukNXJyq3/kiz/3UzCaYq6PskJsaou4=
 go.opentelemetry.io/otel v1.11.1/go.mod h1:1nNhXBbWSD0nsL38H6btgnFN2k4i0sNLHNNMZMSbUGE=
+go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v0.33.0 h1:hlnyYcK61UzruaUssIZvCHl72qSxGB1R55RexLKjFs8=
+go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v0.33.0/go.mod h1:GD6hP1UBb3pVN4IIFH1iMuRiWEVDy1E/7/g1rYQiJyc=
 go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.11.1 h1:3Yvzs7lgOw8MmbxmLRsQGwYdCubFmUHSooKaEhQunFQ=
 go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.11.1/go.mod h1:pyHDt0YlyuENkD2VwHsiRDf+5DfI3EH7pfhUYW6sQUE=
 go.opentelemetry.io/otel/metric v0.33.0 h1:xQAyl7uGEYvrLAiV/09iTJlp1pZnQ9Wl793qbVvED1E=
 go.opentelemetry.io/otel/metric v0.33.0/go.mod h1:QlTYc+EnYNq/M2mNk1qDDMRLpqCOj2f/r5c7Fd5FYaI=
 go.opentelemetry.io/otel/sdk v1.11.1 h1:F7KmQgoHljhUuJyA+9BiU+EkJfyX5nVVF4wyzWZpKxs=
 go.opentelemetry.io/otel/sdk v1.11.1/go.mod h1:/l3FE4SupHJ12TduVjUkZtlfFqDCQJlOlithYrdktys=
+go.opentelemetry.io/otel/sdk/metric v0.33.0 h1:oTqyWfksgKoJmbrs2q7O7ahkJzt+Ipekihf8vhpa9qo=
+go.opentelemetry.io/otel/sdk/metric v0.33.0/go.mod h1:xdypMeA21JBOvjjzDUtD0kzIcHO/SPez+a8HOzJPGp0=
 go.opentelemetry.io/otel/trace v1.11.1 h1:ofxdnzsNrGBYXbP7t7zpUK281+go5rF7dvdIZXF8gdQ=
 go.opentelemetry.io/otel/trace v1.11.1/go.mod h1:f/Q9G7vzk5u91PhbmKbg1Qn0rzH1LJ4vbPHFGkTPtOk=
 golang.org/x/sys v0.0.0-20220919091848-fb04ddd9f9c8 h1:h+EGohizhe9XlX18rfpa8k8RAc5XyaeamM+0VHRd4lc=

instrumentation/net/http/otelhttp/example/server/server.go

@@ -16,27 +16,32 @@ package main
 
 import (
 	"context"
+	"encoding/json"
 	"io"
 	"log"
 	"net/http"
+	"os"
 
 	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
 
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/baggage"
-	stdout "go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
+	stdoutmetric "go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
+	stdouttrace "go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
 	"go.opentelemetry.io/otel/propagation"
+
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/resource"
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
-	semconv "go.opentelemetry.io/otel/semconv/v1.12.0"
+	semconv "go.opentelemetry.io/otel/semconv/v1.10.0"
 	"go.opentelemetry.io/otel/trace"
 )
 
 func initTracer() (*sdktrace.TracerProvider, error) {
 	// Create stdout exporter to be able to retrieve
 	// the collected spans.
-	exporter, err := stdout.New(stdout.WithPrettyPrint())
+	exporter, err := stdouttrace.New(stdouttrace.WithPrettyPrint())
 	if err != nil {
 		return nil, err
 	}
@@ -53,6 +58,17 @@ func initTracer() (*sdktrace.TracerProvider, error) {
 	return tp, err
 }
 
+func initMeter() (*sdkmetric.MeterProvider, error) {
+	enc := json.NewEncoder(os.Stdout)
+	exp, err := stdoutmetric.New(stdoutmetric.WithEncoder(enc))
+	if err != nil {
+		return nil, err
+	}
+
+	mp := sdkmetric.NewMeterProvider(sdkmetric.WithReader(sdkmetric.NewPeriodicReader(exp)))
+	return mp, nil
+}
+
 func main() {
 	tp, err := initTracer()
 	if err != nil {
@@ -64,6 +80,16 @@ func main() {
 		}
 	}()
 
+	mp, err := initMeter()
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer func() {
+		if err := mp.Shutdown(context.Background()); err != nil {
+			log.Printf("Error shutting down meter provider: %v", err)
+		}
+	}()
+
 	uk := attribute.Key("username")
 
 	helloHandler := func(w http.ResponseWriter, req *http.Request) {