Add ClientConn state

clientconn.go

@@ -146,6 +146,7 @@ func Dial(target string, opts ...DialOption) (*ClientConn, error) {
 	}
 	if cc.dopts.block {
 		if err := cc.resetTransport(false); err != nil {
+			cc.Close()
 			return nil, err
 		}
 		// Start to monitor the error status of transport.
@@ -155,6 +156,7 @@ func Dial(target string, opts ...DialOption) (*ClientConn, error) {
 		go func() {
 			if err := cc.resetTransport(false); err != nil {
 				grpclog.Printf("Failed to dial %s: %v; please retry.", target, err)
+				cc.Close()
 				return
 			}
 			go cc.transportMonitor()
@@ -163,6 +165,22 @@ func Dial(target string, opts ...DialOption) (*ClientConn, error) {
 	return cc, nil
 }
 
+// ConnectivityState indicates the state of a client connection.
+type ConnectivityState int
+
+const (
+	// Idle indicates the ClientConn is idle.
+	Idle ConnectivityState = iota
+	// Connecting indicates the ClienConn is connecting.
+	Connecting
+	// Ready indicates the ClientConn is ready for work.
+	Ready
+	// TransientFailure indicates the ClientConn has seen a failure but expects to recover.
+	TransientFailure
+	// Shutdown indicates the CLientConn has stated shutting down.
+	Shutdown
+)
+
 // ClientConn represents a client connection to an RPC service.
 type ClientConn struct {
 	target       string
@@ -171,11 +189,10 @@ type ClientConn struct {
 	shutdownChan chan struct{}
 
 	mu    sync.Mutex
+	state ConnectivityState
 	// ready is closed and becomes nil when a new transport is up or failed
 	// due to timeout.
 	ready chan struct{}
-	// Indicates the ClientConn is under destruction.
-	closing bool
 	// Every time a new transport is created, this is incremented by 1. Used
 	// to avoid trying to recreate a transport while the new one is already
 	// under construction.
@@ -188,11 +205,12 @@ func (cc *ClientConn) resetTransport(closeTransport bool) error {
 	start := time.Now()
 	for {
 		cc.mu.Lock()
+		cc.state = Connecting
 		t := cc.transport
 		ts := cc.transportSeq
 		// Avoid wait() picking up a dying transport unnecessarily.
 		cc.transportSeq = 0
-		if cc.closing {
+		if cc.state == Shutdown {
 			cc.mu.Unlock()
 			return ErrClientConnClosing
 		}
@@ -224,6 +242,9 @@ func (cc *ClientConn) resetTransport(closeTransport bool) error {
 		connectTime := time.Now()
 		newTransport, err := transport.NewClientTransport(cc.target, &copts)
 		if err != nil {
+			cc.mu.Lock()
+			cc.state = TransientFailure
+			cc.mu.Unlock()
 			sleepTime -= time.Since(connectTime)
 			if sleepTime < 0 {
 				sleepTime = 0
@@ -240,12 +261,13 @@ func (cc *ClientConn) resetTransport(closeTransport bool) error {
 			continue
 		}
 		cc.mu.Lock()
-		if cc.closing {
+		if cc.state == Shutdown {
 			// cc.Close() has been invoked.
 			cc.mu.Unlock()
 			newTransport.Close()
 			return ErrClientConnClosing
 		}
+		cc.state = Ready
 		cc.transport = newTransport
 		cc.transportSeq = ts + 1
 		if cc.ready != nil {
@@ -262,13 +284,13 @@ func (cc *ClientConn) resetTransport(closeTransport bool) error {
 func (cc *ClientConn) transportMonitor() {
 	for {
 		select {
-		// shutdownChan is needed to detect the channel teardown when
+		// shutdownChan is needed to detect the teardown when
 		// the ClientConn is idle (i.e., no RPC in flight).
 		case <-cc.shutdownChan:
 			return
 		case <-cc.transport.Error():
 			if err := cc.resetTransport(true); err != nil {
-				// The channel is closing.
+				// The ClientConn is closing.
 				grpclog.Printf("grpc: ClientConn.transportMonitor exits due to: %v", err)
 				return
 			}
@@ -284,7 +306,7 @@ func (cc *ClientConn) wait(ctx context.Context, ts int) (transport.ClientTranspo
 	for {
 		cc.mu.Lock()
 		switch {
-		case cc.closing:
+		case cc.state == Shutdown:
 			cc.mu.Unlock()
 			return nil, 0, ErrClientConnClosing
 		case ts < cc.transportSeq:
@@ -316,10 +338,10 @@ func (cc *ClientConn) wait(ctx context.Context, ts int) (transport.ClientTranspo
 func (cc *ClientConn) Close() error {
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
-	if cc.closing {
+	if cc.state == Shutdown {
 		return ErrClientConnClosing
 	}
-	cc.closing = true
+	cc.state = Shutdown
 	if cc.ready != nil {
 		close(cc.ready)
 		cc.ready = nil