[FIXED] Data race between processMsg() and Stats()

Resolves #520

Signed-off-by: Ivan Kozlovic <[email protected]>

.travis.yml

@@ -16,8 +16,8 @@ install:
 before_script:
 - $(exit $(go fmt ./... | wc -l))
 - go vet ./...
-- misspell -error -locale US .
+- find . -type f -name "*.go" | xargs misspell -error -locale US
 - staticcheck ./...
 script:
 - go test -i -race ./...
-- if [[ "$TRAVIS_GO_VERSION" =~ 1.12 ]]; then ./scripts/cov.sh TRAVIS; else go test -race ./...; fi
+- if [[ "$TRAVIS_GO_VERSION" =~ 1.12 ]]; then ./scripts/cov.sh TRAVIS; else go test -race -v -p=1 ./... --failfast; fi

nats.go

@@ -2164,8 +2164,8 @@ func (nc *Conn) processMsg(data []byte) {
 	nc.subsMu.RLock()
 
 	// Stats
-	nc.InMsgs++
-	nc.InBytes += uint64(len(data))
+	atomic.AddUint64(&nc.InMsgs, 1)
+	atomic.AddUint64(&nc.InBytes, uint64(len(data)))
 
 	sub := nc.subs[nc.ps.ma.sid]
 	if sub == nil {
@@ -3881,18 +3881,16 @@ func (nc *Conn) isDrainingPubs() bool {
 
 // Stats will return a race safe copy of the Statistics section for the connection.
 func (nc *Conn) Stats() Statistics {
-	// Stats are updated either under connection's mu or subsMu mutexes.
-	// Lock both to safely get them.
+	// Stats are updated either under connection's mu or with atomic operations
+	// for inbound stats in processMsg().
 	nc.mu.Lock()
-	nc.subsMu.RLock()
 	stats := Statistics{
-		InMsgs:     nc.InMsgs,
-		InBytes:    nc.InBytes,
+		InMsgs:     atomic.LoadUint64(&nc.InMsgs),
+		InBytes:    atomic.LoadUint64(&nc.InBytes),
 		OutMsgs:    nc.OutMsgs,
 		OutBytes:   nc.OutBytes,
 		Reconnects: nc.Reconnects,
 	}
-	nc.subsMu.RUnlock()
 	nc.mu.Unlock()
 	return stats
 }

nats_test.go

@@ -2181,3 +2181,39 @@ func TestAuthErrorOnReconnect(t *testing.T) {
 		t.Fatalf("Wrong status: %d\n", nc.Status())
 	}
 }
+
+func TestStatsRace(t *testing.T) {
+	o := natsserver.DefaultTestOptions
+	o.Port = -1
+	s := RunServerWithOptions(&o)
+	defer s.Shutdown()
+
+	nc, err := Connect(fmt.Sprintf("nats://%s:%d", o.Host, o.Port))
+	if err != nil {
+		t.Fatalf("Error on connect: %v", err)
+	}
+	defer nc.Close()
+
+	wg := sync.WaitGroup{}
+	wg.Add(1)
+	ch := make(chan bool)
+	go func() {
+		defer wg.Done()
+		for {
+			select {
+			case <-ch:
+				return
+			default:
+				nc.Stats()
+			}
+		}
+	}()
+
+	nc.Subscribe("foo", func(_ *Msg) {})
+	for i := 0; i < 1000; i++ {
+		nc.Publish("foo", []byte("hello"))
+	}
+
+	close(ch)
+	wg.Wait()
+}

scripts/cov.sh

@@ -3,10 +3,10 @@
 
 rm -rf ./cov
 mkdir cov
-go test -v -race -covermode=atomic -coverprofile=./cov/nats.out
-go test -v -race -covermode=atomic -coverprofile=./cov/test.out -coverpkg=github.com/nats-io/nats.go ./test
-go test -v -race -covermode=atomic -coverprofile=./cov/builtin.out -coverpkg=github.com/nats-io/nats.go/encoders/builtin ./test -run EncBuiltin
-go test -v -race -covermode=atomic -coverprofile=./cov/protobuf.out -coverpkg=github.com/nats-io/nats.go/encoders/protobuf ./test -run EncProto
+go test --failfast -v -race -covermode=atomic -coverprofile=./cov/nats.out
+go test --failfast -v -race -covermode=atomic -coverprofile=./cov/test.out -coverpkg=github.com/nats-io/nats.go ./test
+go test --failfast -v -race -covermode=atomic -coverprofile=./cov/builtin.out -coverpkg=github.com/nats-io/nats.go/encoders/builtin ./test -run EncBuiltin
+go test --failfast -v -race -covermode=atomic -coverprofile=./cov/protobuf.out -coverpkg=github.com/nats-io/nats.go/encoders/protobuf ./test -run EncProto
 gocovmerge ./cov/*.out > acc.out
 rm -rf ./cov