otelhttp: Record metrics on timed out requests

CHANGELOG.md

@@ -18,6 +18,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Fix `NewServerHandler` in `go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc` to correctly set the span status depending on the gRPC status. (#4587)
 - Update `go.opentelemetry.io/contrib/detectors/aws/ecs` to fix the task ARN when it is not valid. (#3583)
 - Do not panic in `go.opentelemetry.io/contrib/detectors/aws/ecs` when the container ARN is not valid. (#3583)
+- Fix `http.Handler` metric instrumentation in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` to record metrics on timed out requests. (#4634)
 
 ## [1.21.1/0.46.1/0.15.1/0.1.1] - 2023-11-16
 

instrumentation/net/http/otelhttp/handler.go

@@ -15,6 +15,7 @@
 package otelhttp // import "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
 
 import (
+	"context"
 	"io"
 	"net/http"
 	"time"
@@ -232,13 +233,14 @@ func (h *middleware) serveHTTP(w http.ResponseWriter, r *http.Request, next http
 		attributes = append(attributes, semconv.HTTPStatusCode(rww.statusCode))
 	}
 	o := metric.WithAttributes(attributes...)
-	h.requestBytesCounter.Add(ctx, bw.read, o)
-	h.responseBytesCounter.Add(ctx, rww.written, o)
+	ctxWithoutCancel := withoutCancel(ctx)
+	h.requestBytesCounter.Add(ctxWithoutCancel, bw.read, o)
+	h.responseBytesCounter.Add(ctxWithoutCancel, rww.written, o)
 
 	// Use floating point division here for higher precision (instead of Millisecond method).
 	elapsedTime := float64(time.Since(requestStartTime)) / float64(time.Millisecond)
 
-	h.serverLatencyMeasure.Record(ctx, elapsedTime, o)
+	h.serverLatencyMeasure.Record(ctxWithoutCancel, elapsedTime, o)
 }
 
 func setAfterServeAttributes(span trace.Span, read, wrote int64, statusCode int, rerr, werr error) {
@@ -281,3 +283,34 @@ func WithRouteTag(route string, h http.Handler) http.Handler {
 		h.ServeHTTP(w, r)
 	})
 }
+
+func withoutCancel(parent context.Context) context.Context {
+	if parent == nil {
+		panic("cannot create context from nil parent")
+	}
+	return withoutCancelCtx{parent}
+}
+
+type withoutCancelCtx struct {
+	c context.Context
+}
+
+func (withoutCancelCtx) Deadline() (deadline time.Time, ok bool) {
+	return
+}
+
+func (withoutCancelCtx) Done() <-chan struct{} {
+	return nil
+}
+
+func (withoutCancelCtx) Err() error {
+	return nil
+}
+
+func (w withoutCancelCtx) Value(key any) any {
+	return w.c.Value(key)
+}
+
+func (w withoutCancelCtx) String() string {
+	return "withoutCancel"
+}

instrumentation/net/http/otelhttp/test/handler_test.go

@@ -18,11 +18,13 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"strconv"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -539,3 +541,46 @@ func TestWithRouteTag(t *testing.T) {
 		}
 	}
 }
+
+func TestCtxWithoutCancel(t *testing.T) {
+	reader := metric.NewManualReader()
+	meterProvider := metric.NewMeterProvider(metric.WithReader(reader))
+
+	otelHandler := otelhttp.NewHandler(
+		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			_, err := w.Write([]byte("hello world"))
+			require.NoError(t, err)
+		}), "test_handler", otelhttp.WithMeterProvider(meterProvider))
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	l, err := net.Listen("tcp", "localhost:12345")
+	require.NoError(t, err)
+
+	srv := &http.Server{
+		BaseContext:  func(_ net.Listener) context.Context { return ctx },
+		ReadTimeout:  time.Second,
+		WriteTimeout: 10 * time.Second,
+		Handler:      otelHandler,
+	}
+
+	go func() {
+		// When Shutdown is called, Serve immediately returns ErrServerClosed.
+		assert.Equal(t, http.ErrServerClosed, srv.Serve(l))
+	}()
+
+	t.Cleanup(func() {
+		assert.NoError(t, srv.Shutdown(context.Background()))
+	})
+
+	client := &http.Client{}
+	_, err = client.Get("http://" + l.Addr().String())
+	require.NoError(t, err)
+
+	// Check that some metrics were recorded.
+	rm := metricdata.ResourceMetrics{}
+	err = reader.Collect(ctx, &rm)
+	require.NoError(t, err)
+	require.Len(t, rm.ScopeMetrics, 1)
+}