Use an atomic.Int64 as bodyWrapper read bytes counter (#5080)

* use an atomic.Int64 as bodyWrapper read bytes counter

* add changelog entry

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -19,6 +19,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - The deprecated `ResponseContentLength` constant in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` is removed. (#4894)
 - The deprecated `ServerLatency` constant in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` is removed. (#4894)
 
+### Fixed
+
+- Retrieving the body bytes count in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` does not cause a data race anymore. (#5080)
+
 ## [1.23.0/0.48.0/0.17.0/0.3.0] - 2024-02-06
 
 ### Added

instrumentation/net/http/otelhttp/handler.go

@@ -224,15 +224,15 @@ func (h *middleware) serveHTTP(w http.ResponseWriter, r *http.Request, next http
 
 	next.ServeHTTP(w, r.WithContext(ctx))
 
-	setAfterServeAttributes(span, bw.read, rww.written, rww.statusCode, bw.err, rww.err)
+	setAfterServeAttributes(span, bw.read.Load(), rww.written, rww.statusCode, bw.err, rww.err)
 
 	// Add metrics
 	attributes := append(labeler.Get(), semconvutil.HTTPServerRequestMetrics(h.server, r)...)
 	if rww.statusCode > 0 {
 		attributes = append(attributes, semconv.HTTPStatusCode(rww.statusCode))
 	}
 	o := metric.WithAttributes(attributes...)
-	h.requestBytesCounter.Add(ctx, bw.read, o)
+	h.requestBytesCounter.Add(ctx, bw.read.Load(), o)
 	h.responseBytesCounter.Add(ctx, rww.written, o)
 
 	// Use floating point division here for higher precision (instead of Millisecond method).

instrumentation/net/http/otelhttp/transport.go

@@ -182,7 +182,7 @@ func (t *Transport) RoundTrip(r *http.Request) (*http.Response, error) {
 		metricAttrs = append(metricAttrs, semconv.HTTPStatusCode(res.StatusCode))
 	}
 	o := metric.WithAttributes(metricAttrs...)
-	t.requestBytesCounter.Add(ctx, bw.read, o)
+	t.requestBytesCounter.Add(ctx, bw.read.Load(), o)
 	// For handling response bytes we leverage a callback when the client reads the http response
 	readRecordFunc := func(n int64) {
 		t.responseBytesCounter.Add(ctx, n, o)

instrumentation/net/http/otelhttp/wrap.go

@@ -18,6 +18,7 @@ import (
 	"context"
 	"io"
 	"net/http"
+	"sync/atomic"
 
 	"go.opentelemetry.io/otel/propagation"
 )
@@ -30,14 +31,14 @@ type bodyWrapper struct {
 	io.ReadCloser
 	record func(n int64) // must not be nil
 
-	read int64
+	read atomic.Int64
 	err  error
 }
 
 func (w *bodyWrapper) Read(b []byte) (int, error) {
 	n, err := w.ReadCloser.Read(b)
 	n1 := int64(n)
-	w.read += n1
+	w.read.Add(n1)
 	w.err = err
 	w.record(n1)
 	return n, err