Collector example: add metrics (#5283)

Resolves #5243

CHANGELOG.md

@@ -18,6 +18,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   - An `int64` or `float64` synchronous gauge instrument can now be created from a `Meter`.
   - All implementations of the API (`go.opentelemetry.io/otel/metric/noop`, `go.opentelemetry.io/otel/sdk/metric`) are updated to support this instrument.
 - Add logs to `go.opentelemetry.io/otel/example/dice`. (#5349)
+- Add metrics in the `otel-collector` example. (#5283)
 
 ### Changed
 

example/otel-collector/README.md

@@ -52,7 +52,7 @@ web-browser to view the generated traces.
 
 The Prometheus UI is available at
 [http://localhost:9090](http://localhost:9090). Navigate there in your favorite
-web-browser to view the generated metrics.
+web-browser to view the generated metrics, for instance, `testapp_run_total`.
 
 # Shutting down
 

example/otel-collector/go.mod

@@ -9,8 +9,11 @@ replace (
 
 require (
 	go.opentelemetry.io/otel v1.26.0
+	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc v1.26.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.26.0
+	go.opentelemetry.io/otel/metric v1.26.0
 	go.opentelemetry.io/otel/sdk v1.26.0
+	go.opentelemetry.io/otel/sdk/metric v1.26.0
 	go.opentelemetry.io/otel/trace v1.26.0
 	google.golang.org/grpc v1.64.0
 )
@@ -21,7 +24,6 @@ require (
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.20.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.26.0 // indirect
-	go.opentelemetry.io/otel/metric v1.26.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.2.0 // indirect
 	golang.org/x/net v0.25.0 // indirect
 	golang.org/x/sys v0.20.0 // indirect
@@ -38,3 +40,7 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace => ../../exporters/otl
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../../exporters/otlp/otlptrace/otlptracegrpc
 
 replace go.opentelemetry.io/otel/metric => ../../metric
+
+replace go.opentelemetry.io/otel/sdk/metric => ../../sdk/metric
+
+replace go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../../exporters/otlp/otlpmetric/otlpmetricgrpc

example/otel-collector/main.go

@@ -19,29 +19,22 @@ import (
 
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/metric"
 	"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/v1.24.0"
 	"go.opentelemetry.io/otel/trace"
 )
 
-// Initializes an OTLP exporter, and configures the corresponding trace and
-// metric providers.
-func initProvider() (func(context.Context) error, error) {
-	ctx := context.Background()
-
-	res, err := resource.New(ctx,
-		resource.WithAttributes(
-			// the service name used to display traces in backends
-			semconv.ServiceName("test-service"),
-		),
-	)
-	if err != nil {
-		return nil, fmt.Errorf("failed to create resource: %w", err)
-	}
+var serviceName = semconv.ServiceNameKey.String("test-service")
 
+// Initialize a gRPC connection to be used by both the tracer and meter
+// providers.
+func initConn() (*grpc.ClientConn, error) {
 	// It connects the OpenTelemetry Collector through local gRPC connection.
 	// You may replace `localhost:4317` with your endpoint.
 	conn, err := grpc.NewClient("localhost:4317",
@@ -52,8 +45,13 @@ func initProvider() (func(context.Context) error, error) {
 		return nil, fmt.Errorf("failed to create gRPC connection to collector: %w", err)
 	}
 
+	return conn, err
+}
+
+// Initializes an OTLP exporter, and configures the corresponding trace provider.
+func initTracerProvider(ctx context.Context, res *resource.Resource, conn *grpc.ClientConn) (func(context.Context) error, error) {
 	// Set up a trace exporter
-	traceExporter, err := otlptracegrpc.New(context.Background(), otlptracegrpc.WithGRPCConn(conn))
+	traceExporter, err := otlptracegrpc.New(ctx, otlptracegrpc.WithGRPCConn(conn))
 	if err != nil {
 		return nil, fmt.Errorf("failed to create trace exporter: %w", err)
 	}
@@ -68,30 +66,72 @@ func initProvider() (func(context.Context) error, error) {
 	)
 	otel.SetTracerProvider(tracerProvider)
 
-	// set global propagator to tracecontext (the default is no-op).
+	// Set global propagator to tracecontext (the default is no-op).
 	otel.SetTextMapPropagator(propagation.TraceContext{})
 
 	// Shutdown will flush any remaining spans and shut down the exporter.
 	return tracerProvider.Shutdown, nil
 }
 
+// Initializes an OTLP exporter, and configures the corresponding meter provider.
+func initMeterProvider(ctx context.Context, res *resource.Resource, conn *grpc.ClientConn) (func(context.Context) error, error) {
+	metricExporter, err := otlpmetricgrpc.New(ctx, otlpmetricgrpc.WithGRPCConn(conn))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create metrics exporter: %w", err)
+	}
+
+	meterProvider := sdkmetric.NewMeterProvider(
+		sdkmetric.WithReader(sdkmetric.NewPeriodicReader(metricExporter)),
+		sdkmetric.WithResource(res),
+	)
+	otel.SetMeterProvider(meterProvider)
+
+	return meterProvider.Shutdown, nil
+}
+
 func main() {
 	log.Printf("Waiting for connection...")
 
 	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
 	defer cancel()
 
-	shutdown, err := initProvider()
+	conn, err := initConn()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	res, err := resource.New(ctx,
+		resource.WithAttributes(
+			// The service name used to display traces in backends
+			serviceName,
+		),
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	shutdownTracerProvider, err := initTracerProvider(ctx, res, conn)
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer func() {
-		if err := shutdown(ctx); err != nil {
-			log.Fatal("failed to shutdown TracerProvider: %w", err)
+		if err := shutdownTracerProvider(ctx); err != nil {
+			log.Fatalf("failed to shutdown TracerProvider: %s", err)
+		}
+	}()
+
+	shutdownMeterProvider, err := initMeterProvider(ctx, res, conn)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer func() {
+		if err := shutdownMeterProvider(ctx); err != nil {
+			log.Fatalf("failed to shutdown MeterProvider: %s", err)
 		}
 	}()
 
 	tracer := otel.Tracer("test-tracer")
+	meter := otel.Meter("test-meter")
 
 	// Attributes represent additional key-value descriptors that can be bound
 	// to a metric observer or recorder.
@@ -101,7 +141,12 @@ func main() {
 		attribute.String("attrC", "vanilla"),
 	}
 
-	// work begins
+	runCount, err := meter.Int64Counter("run", metric.WithDescription("The number of times the iteration ran"))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Work begins
 	ctx, span := tracer.Start(
 		ctx,
 		"CollectorExporter-Example",
@@ -109,6 +154,7 @@ func main() {
 	defer span.End()
 	for i := 0; i < 10; i++ {
 		_, iSpan := tracer.Start(ctx, fmt.Sprintf("Sample-%d", i))
+		runCount.Add(ctx, 1, metric.WithAttributes(commonAttrs...))
 		log.Printf("Doing really hard work (%d / 10)\n", i+1)
 
 		<-time.After(time.Second)