clientconn: do not automatically reconnect addrConns; go idle instead (…

…#4613)

balancer/balancer.go

@@ -353,18 +353,20 @@ var ErrBadResolverState = errors.New("bad resolver state")
 //
 // It's not thread safe.
 type ConnectivityStateEvaluator struct {
-	numReady      uint64 // Number of addrConns in ready state.
-	numConnecting uint64 // Number of addrConns in connecting state.
+	numReady            uint64 // Number of addrConns in ready state.
+	numConnecting       uint64 // Number of addrConns in connecting state.
+	numTransientFailure uint64 // Number of addrConns in transient failure state.
 }
 
 // RecordTransition records state change happening in subConn and based on that
 // it evaluates what aggregated state should be.
 //
 //  - If at least one SubConn in Ready, the aggregated state is Ready;
 //  - Else if at least one SubConn in Connecting, the aggregated state is Connecting;
-//  - Else the aggregated state is TransientFailure.
+//  - Else if at least one SubConn is TransientFailure, the aggregated state is Transient Failure;
+//  - Else the aggregated state is Idle
 //
-// Idle and Shutdown are not considered.
+// Shutdown is not considered.
 func (cse *ConnectivityStateEvaluator) RecordTransition(oldState, newState connectivity.State) connectivity.State {
 	// Update counters.
 	for idx, state := range []connectivity.State{oldState, newState} {
@@ -374,6 +376,8 @@ func (cse *ConnectivityStateEvaluator) RecordTransition(oldState, newState conne
 			cse.numReady += updateVal
 		case connectivity.Connecting:
 			cse.numConnecting += updateVal
+		case connectivity.TransientFailure:
+			cse.numTransientFailure += updateVal
 		}
 	}
 
@@ -384,5 +388,8 @@ func (cse *ConnectivityStateEvaluator) RecordTransition(oldState, newState conne
 	if cse.numConnecting > 0 {
 		return connectivity.Connecting
 	}
-	return connectivity.TransientFailure
+	if cse.numTransientFailure > 0 {
+		return connectivity.TransientFailure
+	}
+	return connectivity.Idle
 }

balancer_conn_wrappers.go

@@ -239,25 +239,25 @@ func (acbw *acBalancerWrapper) UpdateAddresses(addrs []resolver.Address) {
 			return
 		}
 
-		ac, err := cc.newAddrConn(addrs, opts)
+		newAC, err := cc.newAddrConn(addrs, opts)
 		if err != nil {
 			channelz.Warningf(logger, acbw.ac.channelzID, "acBalancerWrapper: UpdateAddresses: failed to newAddrConn: %v", err)
 			return
 		}
-		acbw.ac = ac
-		ac.mu.Lock()
-		ac.acbw = acbw
-		ac.mu.Unlock()
+		acbw.ac = newAC
+		newAC.mu.Lock()
+		newAC.acbw = acbw
+		newAC.mu.Unlock()
 		if acState != connectivity.Idle {
-			ac.connect()
+			go newAC.connect()
 		}
 	}
 }
 
 func (acbw *acBalancerWrapper) Connect() {
 	acbw.mu.Lock()
 	defer acbw.mu.Unlock()
-	acbw.ac.connect()
+	go acbw.ac.connect()
 }
 
 func (acbw *acBalancerWrapper) getAddrConn() *addrConn {