Do not create new addrConn when connection error happens (#1369)

clientconn.go

@@ -559,15 +559,16 @@ func (cc *ClientConn) scWatcher() {
 // resetAddrConn creates an addrConn for addr and adds it to cc.conns.
 // If there is an old addrConn for addr, it will be torn down, using tearDownErr as the reason.
 // If tearDownErr is nil, errConnDrain will be used instead.
+//
+// We should never need to replace an addrConn with a new one. This function is only used
+// as newAddrConn to create new addrConn.
+// TODO rename this function and clean up the code.
 func (cc *ClientConn) resetAddrConn(addr Address, block bool, tearDownErr error) error {
 	ac := &addrConn{
 		cc:    cc,
 		addr:  addr,
 		dopts: cc.dopts,
 	}
-	cc.mu.RLock()
-	ac.dopts.copts.KeepaliveParams = cc.mkp
-	cc.mu.RUnlock()
 	ac.ctx, ac.cancel = context.WithCancel(cc.ctx)
 	ac.stateCV = sync.NewCond(&ac.mu)
 	if EnableTracing {
@@ -598,10 +599,7 @@ func (cc *ClientConn) resetAddrConn(addr Address, block bool, tearDownErr error)
 	cc.mu.Unlock()
 	if stale != nil {
 		// There is an addrConn alive on ac.addr already. This could be due to
-		// 1) a buggy Balancer notifies duplicated Addresses;
-		// 2) goaway was received, a new ac will replace the old ac.
-		//    The old ac should be deleted from cc.conns, but the
-		//    underlying transport should drain rather than close.
+		// a buggy Balancer that reports duplicated Addresses.
 		if tearDownErr == nil {
 			// tearDownErr is nil if resetAddrConn is called by
 			// 1) Dial
@@ -828,26 +826,44 @@ func (ac *addrConn) waitForStateChange(ctx context.Context, sourceState Connecti
 	return ac.state, nil
 }
 
-func (ac *addrConn) resetTransport(closeTransport bool) error {
+// resetTransport recreates a transport to the address for ac.
+// For the old transport:
+// - if drain is true, it will be gracefully closed.
+// - otherwise, it will be closed.
+func (ac *addrConn) resetTransport(drain bool) error {
+	ac.mu.Lock()
+	if ac.state == Shutdown {
+		ac.mu.Unlock()
+		return errConnClosing
+	}
+	ac.printf("connecting")
+	if ac.down != nil {
+		ac.down(downErrorf(false, true, "%v", errNetworkIO))
+		ac.down = nil
+	}
+	ac.state = Connecting
+	ac.stateCV.Broadcast()
+	t := ac.transport
+	ac.transport = nil
+	ac.mu.Unlock()
+	if t != nil {
+		if drain {
+			t.GracefulClose()
+		} else {
+			t.Close()
+		}
+	}
+	ac.cc.mu.RLock()
+	ac.dopts.copts.KeepaliveParams = ac.cc.mkp
+	ac.cc.mu.RUnlock()
 	for retries := 0; ; retries++ {
 		ac.mu.Lock()
-		ac.printf("connecting")
 		if ac.state == Shutdown {
 			// ac.tearDown(...) has been invoked.
 			ac.mu.Unlock()
 			return errConnClosing
 		}
-		if ac.down != nil {
-			ac.down(downErrorf(false, true, "%v", errNetworkIO))
-			ac.down = nil
-		}
-		ac.state = Connecting
-		ac.stateCV.Broadcast()
-		t := ac.transport
 		ac.mu.Unlock()
-		if closeTransport && t != nil {
-			t.Close()
-		}
 		sleepTime := ac.dopts.bs.backoff(retries)
 		timeout := minConnectTimeout
 		if timeout < sleepTime {
@@ -883,7 +899,6 @@ func (ac *addrConn) resetTransport(closeTransport bool) error {
 				ac.ready = nil
 			}
 			ac.mu.Unlock()
-			closeTransport = false
 			timer := time.NewTimer(sleepTime - time.Since(connectTime))
 			select {
 			case <-timer.C:
@@ -936,28 +951,40 @@ func (ac *addrConn) transportMonitor() {
 			return
 		case <-t.GoAway():
 			ac.adjustParams(t.GetGoAwayReason())
-			// If GoAway happens without any network I/O error, ac is closed without shutting down the
-			// underlying transport (the transport will be closed when all the pending RPCs finished or
-			// failed.).
-			// If GoAway and some network I/O error happen concurrently, ac and its underlying transport
-			// are closed.
-			// In both cases, a new ac is created.
+			// If GoAway happens without any network I/O error, the underlying transport
+			// will be gracefully closed, and a new transport will be created.
+			// (The transport will be closed when all the pending RPCs finished or failed.)
+			// If GoAway and some network I/O error happen concurrently, the underlying transport
+			// will be closed, and a new transport will be created.
+			var drain bool
 			select {
 			case <-t.Error():
-				ac.cc.resetAddrConn(ac.addr, false, errNetworkIO)
 			default:
-				ac.cc.resetAddrConn(ac.addr, false, errConnDrain)
+				drain = true
+			}
+			if err := ac.resetTransport(drain); err != nil {
+				grpclog.Infof("get error from resetTransport %v, transportMonitor returning", err)
+				if err != errConnClosing {
+					// Keep this ac in cc.conns, to get the reason it's torn down.
+					ac.tearDown(err)
+				}
+				return
 			}
-			return
 		case <-t.Error():
 			select {
 			case <-ac.ctx.Done():
 				t.Close()
 				return
 			case <-t.GoAway():
 				ac.adjustParams(t.GetGoAwayReason())
-				ac.cc.resetAddrConn(ac.addr, false, errNetworkIO)
-				return
+				if err := ac.resetTransport(false); err != nil {
+					grpclog.Infof("get error from resetTransport %v, transportMonitor returning", err)
+					if err != errConnClosing {
+						// Keep this ac in cc.conns, to get the reason it's torn down.
+						ac.tearDown(err)
+					}
+					return
+				}
 			default:
 			}
 			ac.mu.Lock()
@@ -969,7 +996,8 @@ func (ac *addrConn) transportMonitor() {
 			ac.state = TransientFailure
 			ac.stateCV.Broadcast()
 			ac.mu.Unlock()
-			if err := ac.resetTransport(true); err != nil {
+			if err := ac.resetTransport(false); err != nil {
+				grpclog.Infof("get error from resetTransport %v, transportMonitor returning", err)
 				ac.mu.Lock()
 				ac.printf("transport exiting: %v", err)
 				ac.mu.Unlock()