[net/http] enhance otelhttp example to support metric (#2610)

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

Signed-off-by: Ziqi Zhao <zhaoziqi9146@gmail.com>
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -12,6 +12,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - The `WithLogger` option to `go.opentelemetry.io/contrib/samplers/jaegerremote` to allow users to pass a `logr.Logger` and have operations logged. (#2566)
 - Add the `messaging.url` & `messaging.system` attributes to all appropriate SQS operations in the `go.opentelemetry.io/contrib/instrumentation/github.com/aws/aws-sdk-go-v2/otelaws` package. (#2879)
+- Add example use of the metrics signal to `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp/example`. (#2610)
 
 ### Fixed
 

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

@@ -7,15 +7,17 @@ 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/metric v0.33.0
 	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
 )
 
 require (
 	github.com/felixge/httpsnoop v1.0.3 // indirect
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
-	go.opentelemetry.io/otel/metric v0.33.0 // indirect
 	golang.org/x/sys v0.0.0-20220919091848-fb04ddd9f9c8 // indirect
 )

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

@@ -25,8 +25,12 @@ import (
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/baggage"
-	stdout "go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
+	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
+	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
 	"go.opentelemetry.io/otel/propagation"
+
+	"go.opentelemetry.io/otel/metric/global"
+	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"
@@ -36,7 +40,7 @@ import (
 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 +57,17 @@ func initTracer() (*sdktrace.TracerProvider, error) {
 	return tp, err
 }
 
+func initMeter() (*sdkmetric.MeterProvider, error) {
+	exp, err := stdoutmetric.New()
+	if err != nil {
+		return nil, err
+	}
+
+	mp := sdkmetric.NewMeterProvider(sdkmetric.WithReader(sdkmetric.NewPeriodicReader(exp)))
+	global.SetMeterProvider(mp)
+	return mp, nil
+}
+
 func main() {
 	tp, err := initTracer()
 	if err != nil {
@@ -64,6 +79,16 @@ 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) {