vendor: update grpc/grpc-go for clientconn patch

cmd/vendor/google.golang.org/grpc/clientconn.go

@@ -73,7 +73,9 @@ var (
 	errConnDrain = errors.New("grpc: the connection is drained")
 	// errConnClosing indicates that the connection is closing.
 	errConnClosing = errors.New("grpc: the connection is closing")
-	errNoAddr      = errors.New("grpc: there is no address available to dial")
+	// errConnUnavailable indicates that the connection is unavailable.
+	errConnUnavailable = errors.New("grpc: the connection is unavailable")
+	errNoAddr          = errors.New("grpc: there is no address available to dial")
 	// minimum time to give a connection to complete
 	minConnectTimeout = 20 * time.Second
 )
@@ -213,9 +215,14 @@ func WithUserAgent(s string) DialOption {
 	}
 }
 
-// Dial creates a client connection the given target.
+// Dial creates a client connection to the given target.
 func Dial(target string, opts ...DialOption) (*ClientConn, error) {
-	ctx := context.Background()
+	return DialContext(context.Background(), target, opts...)
+}
+
+// DialContext creates a client connection to the given target
+// using the supplied context.
+func DialContext(ctx context.Context, target string, opts ...DialOption) (*ClientConn, error) {
 	cc := &ClientConn{
 		target: target,
 		conns:  make(map[Address]*addrConn),
@@ -472,6 +479,10 @@ func (cc *ClientConn) getTransport(ctx context.Context, opts BalancerGetOptions)
 	if cc.dopts.balancer == nil {
 		// If balancer is nil, there should be only one addrConn available.
 		cc.mu.RLock()
+		if cc.conns == nil {
+			cc.mu.RUnlock()
+			return nil, nil, toRPCErr(ErrClientConnClosing)
+		}
 		for _, ac = range cc.conns {
 			// Break after the first iteration to get the first addrConn.
 			ok = true
@@ -501,11 +512,7 @@ func (cc *ClientConn) getTransport(ctx context.Context, opts BalancerGetOptions)
 		}
 		return nil, nil, errConnClosing
 	}
-	// ac.wait should block on transient failure only if balancer is nil and RPC is non-failfast.
-	//  - If RPC is failfast, ac.wait should not block.
-	//  - If balancer is not nil, ac.wait should return errConnClosing on transient failure
-	//    so that non-failfast RPCs will try to get a new transport instead of waiting on ac.
-	t, err := ac.wait(ctx, cc.dopts.balancer == nil && opts.BlockingWait)
+	t, err := ac.wait(ctx, cc.dopts.balancer != nil, !opts.BlockingWait)
 	if err != nil {
 		if put != nil {
 			put()
@@ -757,36 +764,42 @@ func (ac *addrConn) transportMonitor() {
 }
 
 // wait blocks until i) the new transport is up or ii) ctx is done or iii) ac is closed or
-// iv) transport is in TransientFailure and blocking is false.
-func (ac *addrConn) wait(ctx context.Context, blocking bool) (transport.ClientTransport, error) {
+// iv) transport is in TransientFailure and there's no balancer/failfast is true.
+func (ac *addrConn) wait(ctx context.Context, hasBalancer, failfast bool) (transport.ClientTransport, error) {
 	for {
 		ac.mu.Lock()
 		switch {
 		case ac.state == Shutdown:
-			err := ac.tearDownErr
+			if failfast || !hasBalancer {
+				// RPC is failfast or balancer is nil. This RPC should fail with ac.tearDownErr.
+				err := ac.tearDownErr
+				ac.mu.Unlock()
+				return nil, err
+			}
 			ac.mu.Unlock()
-			return nil, err
+			return nil, errConnClosing
 		case ac.state == Ready:
 			ct := ac.transport
 			ac.mu.Unlock()
 			return ct, nil
-		case ac.state == TransientFailure && !blocking:
-			ac.mu.Unlock()
-			return nil, errConnClosing
-		default:
-			ready := ac.ready
-			if ready == nil {
-				ready = make(chan struct{})
-				ac.ready = ready
-			}
-			ac.mu.Unlock()
-			select {
-			case <-ctx.Done():
-				return nil, toRPCErr(ctx.Err())
-			// Wait until the new transport is ready or failed.
-			case <-ready:
+		case ac.state == TransientFailure:
+			if failfast || hasBalancer {
+				ac.mu.Unlock()
+				return nil, errConnUnavailable
 			}
 		}
+		ready := ac.ready
+		if ready == nil {
+			ready = make(chan struct{})
+			ac.ready = ready
+		}
+		ac.mu.Unlock()
+		select {
+		case <-ctx.Done():
+			return nil, toRPCErr(ctx.Err())
+		// Wait until the new transport is ready or failed.
+		case <-ready:
+		}
 	}
 }