simplify disconnected stream detection

weed/messaging/broker/broker_grpc_server_subscribe.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"io"
 	"strings"
-	"sync"
 	"time"
 
 	"github.com/golang/protobuf/proto"
@@ -50,23 +49,13 @@ func (broker *MessageBroker) Subscribe(stream messaging_pb.SeaweedMessaging_Subs
 	defer broker.topicManager.ReleaseLock(tp, false)
 
 	isConnected := true
-	var streamLock sync.Mutex // https://github.com/grpc/grpc-go/issues/948
 	go func() {
-		lastActiveTime := time.Now().UnixNano()
-		sleepTime := 1737 * time.Millisecond
 		for isConnected {
-			time.Sleep(sleepTime)
-			if lastActiveTime != processedTsNs {
-				lastActiveTime = processedTsNs
-				continue
-			}
-			streamLock.Lock()
-			// println("checking connection health to", subscriberId, tp.String())
-			if err = stream.Send(&messaging_pb.BrokerMessage{}); err != nil {
+			if _, err := stream.Recv(); err != nil {
+				println("disconnecting connection to", subscriberId, tp.String())
 				isConnected = false
 				lock.cond.Signal()
 			}
-			streamLock.Unlock()
 		}
 	}()
 
@@ -82,11 +71,9 @@ func (broker *MessageBroker) Subscribe(stream messaging_pb.SeaweedMessaging_Subs
 	// how to process each message
 	// an error returned will end the subscription
 	eachMessageFn := func(m *messaging_pb.Message) error {
-		streamLock.Lock()
 		err := stream.Send(&messaging_pb.BrokerMessage{
 			Data: m,
 		})
-		streamLock.Unlock()
 		if err != nil {
 			glog.V(0).Infof("=> subscriber %v: %+v", subscriberId, err)
 		}