fix: http stats race in traffic metering (#12956)

Traffic metering was not protected against concurrent updates.

```
WARNING: DATA RACE
Read at 0x00c02b0dace8 by goroutine 235:
  github.com/minio/minio/cmd.setHTTPStatsHandler.func1()
      d:/minio/minio/cmd/generic-handlers.go:360 +0x27d
  net/http.HandlerFunc.ServeHTTP()
...

Previous write at 0x00c02b0dace8 by goroutine 994:
  github.com/minio/minio/internal/http/stats.(*IncomingTrafficMeter).Read()
      d:/minio/minio/internal/http/stats/http-traffic-recorder.go:34 +0xd2

```

cmd/http-stats.go

@@ -38,12 +38,12 @@ type ConnStats struct {
 }
 
 // Increase total input bytes
-func (s *ConnStats) incInputBytes(n int) {
+func (s *ConnStats) incInputBytes(n int64) {
 	atomic.AddUint64(&s.totalInputBytes, uint64(n))
 }
 
 // Increase total output bytes
-func (s *ConnStats) incOutputBytes(n int) {
+func (s *ConnStats) incOutputBytes(n int64) {
 	atomic.AddUint64(&s.totalOutputBytes, uint64(n))
 }
 
@@ -58,12 +58,12 @@ func (s *ConnStats) getTotalOutputBytes() uint64 {
 }
 
 // Increase outbound input bytes
-func (s *ConnStats) incS3InputBytes(n int) {
+func (s *ConnStats) incS3InputBytes(n int64) {
 	atomic.AddUint64(&s.s3InputBytes, uint64(n))
 }
 
 // Increase outbound output bytes
-func (s *ConnStats) incS3OutputBytes(n int) {
+func (s *ConnStats) incS3OutputBytes(n int64) {
 	atomic.AddUint64(&s.s3OutputBytes, uint64(n))
 }
 

internal/http/stats/http-traffic-recorder.go

@@ -20,37 +20,39 @@ package stats
 import (
 	"io"
 	"net/http"
+	"sync/atomic"
 )
 
 // IncomingTrafficMeter counts the incoming bytes from the underlying request.Body.
 type IncomingTrafficMeter struct {
+	countBytes int64
 	io.ReadCloser
-	countBytes int
 }
 
 // Read calls the underlying Read and counts the transferred bytes.
 func (r *IncomingTrafficMeter) Read(p []byte) (n int, err error) {
 	n, err = r.ReadCloser.Read(p)
-	r.countBytes += n
+	atomic.AddInt64(&r.countBytes, int64(n))
+
 	return n, err
 }
 
 // BytesCount returns the number of transferred bytes
-func (r IncomingTrafficMeter) BytesCount() int {
+func (r IncomingTrafficMeter) BytesCount() int64 {
-	return r.countBytes
+	return atomic.LoadInt64(&r.countBytes)
 }
 
 // OutgoingTrafficMeter counts the outgoing bytes through the responseWriter.
 type OutgoingTrafficMeter struct {
+	countBytes int64
 	// wrapper for underlying http.ResponseWriter.
 	http.ResponseWriter
-	countBytes int
 }
 
 // Write calls the underlying write and counts the output bytes
 func (w *OutgoingTrafficMeter) Write(p []byte) (n int, err error) {
 	n, err = w.ResponseWriter.Write(p)
-	w.countBytes += n
+	atomic.AddInt64(&w.countBytes, int64(n))
 	return n, err
 }
 
@@ -60,6 +62,6 @@ func (w *OutgoingTrafficMeter) Flush() {
 }
 
 // BytesCount returns the number of transferred bytes
-func (w OutgoingTrafficMeter) BytesCount() int {
+func (w OutgoingTrafficMeter) BytesCount() int64 {
-	return w.countBytes
+	return atomic.LoadInt64(&w.countBytes)
 }