Bump buildkit to master and fix versions incompatible with go mod 1.13

Bump github.com/gogo/googleapis to v1.3.2
Bump github.com/docker/cli to master

Signed-off-by: Silvin Lubecki <silvin.lubecki@docker.com>

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

@@ -31,7 +31,7 @@ import (
 	"time"
 
 	"google.golang.org/grpc/balancer"
-	_ "google.golang.org/grpc/balancer/roundrobin" // To register roundrobin.
+	"google.golang.org/grpc/balancer/base"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/connectivity"
 	"google.golang.org/grpc/credentials"
@@ -42,10 +42,12 @@ import (
 	"google.golang.org/grpc/internal/transport"
 	"google.golang.org/grpc/keepalive"
 	"google.golang.org/grpc/resolver"
-	_ "google.golang.org/grpc/resolver/dns"         // To register dns resolver.
-	_ "google.golang.org/grpc/resolver/passthrough" // To register passthrough resolver.
 	"google.golang.org/grpc/serviceconfig"
 	"google.golang.org/grpc/status"
+
+	_ "google.golang.org/grpc/balancer/roundrobin"           // To register roundrobin.
+	_ "google.golang.org/grpc/internal/resolver/dns"         // To register dns resolver.
+	_ "google.golang.org/grpc/internal/resolver/passthrough" // To register passthrough resolver.
 )
 
 const (
@@ -186,11 +188,11 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	}
 
 	if cc.dopts.defaultServiceConfigRawJSON != nil {
-		sc, err := parseServiceConfig(*cc.dopts.defaultServiceConfigRawJSON)
-		if err != nil {
-			return nil, fmt.Errorf("%s: %v", invalidDefaultServiceConfigErrPrefix, err)
+		scpr := parseServiceConfig(*cc.dopts.defaultServiceConfigRawJSON)
+		if scpr.Err != nil {
+			return nil, fmt.Errorf("%s: %v", invalidDefaultServiceConfigErrPrefix, scpr.Err)
 		}
-		cc.dopts.defaultServiceConfig = sc
+		cc.dopts.defaultServiceConfig, _ = scpr.Config.(*ServiceConfig)
 	}
 	cc.mkp = cc.dopts.copts.KeepaliveParams
 
@@ -235,29 +237,28 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 		}
 	}
 	if cc.dopts.bs == nil {
-		cc.dopts.bs = backoff.Exponential{
-			MaxDelay: DefaultBackoffConfig.MaxDelay,
+		cc.dopts.bs = backoff.DefaultExponential
+	}
+
+	// Determine the resolver to use.
+	cc.parsedTarget = parseTarget(cc.target)
+	grpclog.Infof("parsed scheme: %q", cc.parsedTarget.Scheme)
+	resolverBuilder := cc.getResolver(cc.parsedTarget.Scheme)
+	if resolverBuilder == nil {
+		// If resolver builder is still nil, the parsed target's scheme is
+		// not registered. Fallback to default resolver and set Endpoint to
+		// the original target.
+		grpclog.Infof("scheme %q not registered, fallback to default scheme", cc.parsedTarget.Scheme)
+		cc.parsedTarget = resolver.Target{
+			Scheme:   resolver.GetDefaultScheme(),
+			Endpoint: target,
+		}
+		resolverBuilder = cc.getResolver(cc.parsedTarget.Scheme)
+		if resolverBuilder == nil {
+			return nil, fmt.Errorf("could not get resolver for default scheme: %q", cc.parsedTarget.Scheme)
 		}
 	}
-	if cc.dopts.resolverBuilder == nil {
-		// Only try to parse target when resolver builder is not already set.
-		cc.parsedTarget = parseTarget(cc.target)
-		grpclog.Infof("parsed scheme: %q", cc.parsedTarget.Scheme)
-		cc.dopts.resolverBuilder = resolver.Get(cc.parsedTarget.Scheme)
-		if cc.dopts.resolverBuilder == nil {
-			// If resolver builder is still nil, the parsed target's scheme is
-			// not registered. Fallback to default resolver and set Endpoint to
-			// the original target.
-			grpclog.Infof("scheme %q not registered, fallback to default scheme", cc.parsedTarget.Scheme)
-			cc.parsedTarget = resolver.Target{
-				Scheme:   resolver.GetDefaultScheme(),
-				Endpoint: target,
-			}
-			cc.dopts.resolverBuilder = resolver.Get(cc.parsedTarget.Scheme)
-		}
-	} else {
-		cc.parsedTarget = resolver.Target{Endpoint: target}
-	}
+
 	creds := cc.dopts.copts.TransportCredentials
 	if creds != nil && creds.Info().ServerName != "" {
 		cc.authority = creds.Info().ServerName
@@ -297,14 +298,14 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	}
 
 	// Build the resolver.
-	rWrapper, err := newCCResolverWrapper(cc)
+	rWrapper, err := newCCResolverWrapper(cc, resolverBuilder)
 	if err != nil {
 		return nil, fmt.Errorf("failed to build resolver: %v", err)
 	}
-
 	cc.mu.Lock()
 	cc.resolverWrapper = rWrapper
 	cc.mu.Unlock()
+
 	// A blocking dial blocks until the clientConn is ready.
 	if cc.dopts.block {
 		for {
@@ -443,7 +444,32 @@ func (csm *connectivityStateManager) getNotifyChan() <-chan struct{} {
 	return csm.notifyChan
 }
 
-// ClientConn represents a client connection to an RPC server.
+// ClientConnInterface defines the functions clients need to perform unary and
+// streaming RPCs.  It is implemented by *ClientConn, and is only intended to
+// be referenced by generated code.
+type ClientConnInterface interface {
+	// Invoke performs a unary RPC and returns after the response is received
+	// into reply.
+	Invoke(ctx context.Context, method string, args interface{}, reply interface{}, opts ...CallOption) error
+	// NewStream begins a streaming RPC.
+	NewStream(ctx context.Context, desc *StreamDesc, method string, opts ...CallOption) (ClientStream, error)
+}
+
+// Assert *ClientConn implements ClientConnInterface.
+var _ ClientConnInterface = (*ClientConn)(nil)
+
+// ClientConn represents a virtual connection to a conceptual endpoint, to
+// perform RPCs.
+//
+// A ClientConn is free to have zero or more actual connections to the endpoint
+// based on configuration, load, etc. It is also free to determine which actual
+// endpoints to use and may change it every RPC, permitting client-side load
+// balancing.
+//
+// A ClientConn encapsulates a range of functionality including name
+// resolution, TCP connection establishment (with retries and backoff) and TLS
+// handshakes. It also handles errors on established connections by
+// re-resolving the name and reconnecting.
 type ClientConn struct {
 	ctx    context.Context
 	cancel context.CancelFunc
@@ -532,58 +558,104 @@ func (cc *ClientConn) waitForResolvedAddrs(ctx context.Context) error {
 	}
 }
 
-func (cc *ClientConn) updateResolverState(s resolver.State) error {
+var emptyServiceConfig *ServiceConfig
+
+func init() {
+	cfg := parseServiceConfig("{}")
+	if cfg.Err != nil {
+		panic(fmt.Sprintf("impossible error parsing empty service config: %v", cfg.Err))
+	}
+	emptyServiceConfig = cfg.Config.(*ServiceConfig)
+}
+
+func (cc *ClientConn) maybeApplyDefaultServiceConfig(addrs []resolver.Address) {
+	if cc.sc != nil {
+		cc.applyServiceConfigAndBalancer(cc.sc, addrs)
+		return
+	}
+	if cc.dopts.defaultServiceConfig != nil {
+		cc.applyServiceConfigAndBalancer(cc.dopts.defaultServiceConfig, addrs)
+	} else {
+		cc.applyServiceConfigAndBalancer(emptyServiceConfig, addrs)
+	}
+}
+
+func (cc *ClientConn) updateResolverState(s resolver.State, err error) error {
+	defer cc.firstResolveEvent.Fire()
 	cc.mu.Lock()
-	defer cc.mu.Unlock()
 	// Check if the ClientConn is already closed. Some fields (e.g.
 	// balancerWrapper) are set to nil when closing the ClientConn, and could
 	// cause nil pointer panic if we don't have this check.
 	if cc.conns == nil {
+		cc.mu.Unlock()
 		return nil
 	}
 
-	if cc.dopts.disableServiceConfig || s.ServiceConfig == nil {
-		if cc.dopts.defaultServiceConfig != nil && cc.sc == nil {
-			cc.applyServiceConfig(cc.dopts.defaultServiceConfig)
+	if err != nil {
+		// May need to apply the initial service config in case the resolver
+		// doesn't support service configs, or doesn't provide a service config
+		// with the new addresses.
+		cc.maybeApplyDefaultServiceConfig(nil)
+
+		if cc.balancerWrapper != nil {
+			cc.balancerWrapper.resolverError(err)
+		}
+
+		// No addresses are valid with err set; return early.
+		cc.mu.Unlock()
+		return balancer.ErrBadResolverState
+	}
+
+	var ret error
+	if cc.dopts.disableServiceConfig || s.ServiceConfig == nil {
+		cc.maybeApplyDefaultServiceConfig(s.Addresses)
+		// TODO: do we need to apply a failing LB policy if there is no
+		// default, per the error handling design?
+	} else {
+		if sc, ok := s.ServiceConfig.Config.(*ServiceConfig); s.ServiceConfig.Err == nil && ok {
+			cc.applyServiceConfigAndBalancer(sc, s.Addresses)
+		} else {
+			ret = balancer.ErrBadResolverState
+			if cc.balancerWrapper == nil {
+				var err error
+				if s.ServiceConfig.Err != nil {
+					err = status.Errorf(codes.Unavailable, "error parsing service config: %v", s.ServiceConfig.Err)
+				} else {
+					err = status.Errorf(codes.Unavailable, "illegal service config type: %T", s.ServiceConfig.Config)
+				}
+				cc.blockingpicker.updatePicker(base.NewErrPicker(err))
+				cc.csMgr.updateState(connectivity.TransientFailure)
+				cc.mu.Unlock()
+				return ret
+			}
 		}
-	} else if sc, ok := s.ServiceConfig.(*ServiceConfig); ok {
-		cc.applyServiceConfig(sc)
 	}
 
 	var balCfg serviceconfig.LoadBalancingConfig
-	if cc.dopts.balancerBuilder == nil {
-		// Only look at balancer types and switch balancer if balancer dial
-		// option is not set.
-		var newBalancerName string
-		if cc.sc != nil && cc.sc.lbConfig != nil {
-			newBalancerName = cc.sc.lbConfig.name
-			balCfg = cc.sc.lbConfig.cfg
-		} else {
-			var isGRPCLB bool
-			for _, a := range s.Addresses {
-				if a.Type == resolver.GRPCLB {
-					isGRPCLB = true
-					break
-				}
-			}
-			if isGRPCLB {
-				newBalancerName = grpclbName
-			} else if cc.sc != nil && cc.sc.LB != nil {
-				newBalancerName = *cc.sc.LB
-			} else {
-				newBalancerName = PickFirstBalancerName
-			}
-		}
-		cc.switchBalancer(newBalancerName)
-	} else if cc.balancerWrapper == nil {
-		// Balancer dial option was set, and this is the first time handling
-		// resolved addresses. Build a balancer with dopts.balancerBuilder.
-		cc.curBalancerName = cc.dopts.balancerBuilder.Name()
-		cc.balancerWrapper = newCCBalancerWrapper(cc, cc.dopts.balancerBuilder, cc.balancerBuildOpts)
+	if cc.dopts.balancerBuilder == nil && cc.sc != nil && cc.sc.lbConfig != nil {
+		balCfg = cc.sc.lbConfig.cfg
 	}
 
-	cc.balancerWrapper.updateClientConnState(&balancer.ClientConnState{ResolverState: s, BalancerConfig: balCfg})
-	return nil
+	cbn := cc.curBalancerName
+	bw := cc.balancerWrapper
+	cc.mu.Unlock()
+	if cbn != grpclbName {
+		// Filter any grpclb addresses since we don't have the grpclb balancer.
+		for i := 0; i < len(s.Addresses); {
+			if s.Addresses[i].Type == resolver.GRPCLB {
+				copy(s.Addresses[i:], s.Addresses[i+1:])
+				s.Addresses = s.Addresses[:len(s.Addresses)-1]
+				continue
+			}
+			i++
+		}
+	}
+	uccsErr := bw.updateClientConnState(&balancer.ClientConnState{ResolverState: s, BalancerConfig: balCfg})
+	if ret == nil {
+		ret = uccsErr // prefer ErrBadResolver state since any other error is
+		// currently meaningless to the caller.
+	}
+	return ret
 }
 
 // switchBalancer starts the switching from current balancer to the balancer
@@ -631,7 +703,7 @@ func (cc *ClientConn) switchBalancer(name string) {
 	cc.balancerWrapper = newCCBalancerWrapper(cc, builder, cc.balancerBuildOpts)
 }
 
-func (cc *ClientConn) handleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
+func (cc *ClientConn) handleSubConnStateChange(sc balancer.SubConn, s connectivity.State, err error) {
 	cc.mu.Lock()
 	if cc.conns == nil {
 		cc.mu.Unlock()
@@ -639,7 +711,7 @@ func (cc *ClientConn) handleSubConnStateChange(sc balancer.SubConn, s connectivi
 	}
 	// TODO(bar switching) send updates to all balancer wrappers when balancer
 	// gracefully switching is supported.
-	cc.balancerWrapper.handleSubConnStateChange(sc, s)
+	cc.balancerWrapper.handleSubConnStateChange(sc, s, err)
 	cc.mu.Unlock()
 }
 
@@ -736,7 +808,7 @@ func (ac *addrConn) connect() error {
 	}
 	// Update connectivity state within the lock to prevent subsequent or
 	// concurrent calls from resetting the transport more than once.
-	ac.updateConnectivityState(connectivity.Connecting)
+	ac.updateConnectivityState(connectivity.Connecting, nil)
 	ac.mu.Unlock()
 
 	// Start a goroutine connecting to the server asynchronously.
@@ -822,7 +894,8 @@ func (cc *ClientConn) healthCheckConfig() *healthCheckConfig {
 }
 
 func (cc *ClientConn) getTransport(ctx context.Context, failfast bool, method string) (transport.ClientTransport, func(balancer.DoneInfo), error) {
-	t, done, err := cc.blockingpicker.pick(ctx, failfast, balancer.PickOptions{
+	t, done, err := cc.blockingpicker.pick(ctx, failfast, balancer.PickInfo{
+		Ctx:            ctx,
 		FullMethodName: method,
 	})
 	if err != nil {
@@ -831,10 +904,10 @@ func (cc *ClientConn) getTransport(ctx context.Context, failfast bool, method st
 	return t, done, nil
 }
 
-func (cc *ClientConn) applyServiceConfig(sc *ServiceConfig) error {
+func (cc *ClientConn) applyServiceConfigAndBalancer(sc *ServiceConfig, addrs []resolver.Address) {
 	if sc == nil {
 		// should never reach here.
-		return fmt.Errorf("got nil pointer for service config")
+		return
 	}
 	cc.sc = sc
 
@@ -850,10 +923,38 @@ func (cc *ClientConn) applyServiceConfig(sc *ServiceConfig) error {
 		cc.retryThrottler.Store((*retryThrottler)(nil))
 	}
 
-	return nil
+	if cc.dopts.balancerBuilder == nil {
+		// Only look at balancer types and switch balancer if balancer dial
+		// option is not set.
+		var newBalancerName string
+		if cc.sc != nil && cc.sc.lbConfig != nil {
+			newBalancerName = cc.sc.lbConfig.name
+		} else {
+			var isGRPCLB bool
+			for _, a := range addrs {
+				if a.Type == resolver.GRPCLB {
+					isGRPCLB = true
+					break
+				}
+			}
+			if isGRPCLB {
+				newBalancerName = grpclbName
+			} else if cc.sc != nil && cc.sc.LB != nil {
+				newBalancerName = *cc.sc.LB
+			} else {
+				newBalancerName = PickFirstBalancerName
+			}
+		}
+		cc.switchBalancer(newBalancerName)
+	} else if cc.balancerWrapper == nil {
+		// Balancer dial option was set, and this is the first time handling
+		// resolved addresses. Build a balancer with dopts.balancerBuilder.
+		cc.curBalancerName = cc.dopts.balancerBuilder.Name()
+		cc.balancerWrapper = newCCBalancerWrapper(cc, cc.dopts.balancerBuilder, cc.balancerBuildOpts)
+	}
 }
 
-func (cc *ClientConn) resolveNow(o resolver.ResolveNowOption) {
+func (cc *ClientConn) resolveNow(o resolver.ResolveNowOptions) {
 	cc.mu.RLock()
 	r := cc.resolverWrapper
 	cc.mu.RUnlock()
@@ -875,8 +976,9 @@ func (cc *ClientConn) resolveNow(o resolver.ResolveNowOption) {
 // This API is EXPERIMENTAL.
 func (cc *ClientConn) ResetConnectBackoff() {
 	cc.mu.Lock()
-	defer cc.mu.Unlock()
-	for ac := range cc.conns {
+	conns := cc.conns
+	cc.mu.Unlock()
+	for ac := range conns {
 		ac.resetConnectBackoff()
 	}
 }
@@ -962,7 +1064,7 @@ type addrConn struct {
 }
 
 // Note: this requires a lock on ac.mu.
-func (ac *addrConn) updateConnectivityState(s connectivity.State) {
+func (ac *addrConn) updateConnectivityState(s connectivity.State, lastErr error) {
 	if ac.state == s {
 		return
 	}
@@ -975,7 +1077,7 @@ func (ac *addrConn) updateConnectivityState(s connectivity.State) {
 			Severity: channelz.CtINFO,
 		})
 	}
-	ac.cc.handleSubConnStateChange(ac.acbw, s)
+	ac.cc.handleSubConnStateChange(ac.acbw, s, lastErr)
 }
 
 // adjustParams updates parameters used to create transports upon
@@ -995,7 +1097,7 @@ func (ac *addrConn) adjustParams(r transport.GoAwayReason) {
 func (ac *addrConn) resetTransport() {
 	for i := 0; ; i++ {
 		if i > 0 {
-			ac.cc.resolveNow(resolver.ResolveNowOption{})
+			ac.cc.resolveNow(resolver.ResolveNowOptions{})
 		}
 
 		ac.mu.Lock()
@@ -1024,7 +1126,7 @@ func (ac *addrConn) resetTransport() {
 		// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md#proposed-backoff-algorithm
 		connectDeadline := time.Now().Add(dialDuration)
 
-		ac.updateConnectivityState(connectivity.Connecting)
+		ac.updateConnectivityState(connectivity.Connecting, nil)
 		ac.transport = nil
 		ac.mu.Unlock()
 
@@ -1037,7 +1139,7 @@ func (ac *addrConn) resetTransport() {
 				ac.mu.Unlock()
 				return
 			}
-			ac.updateConnectivityState(connectivity.TransientFailure)
+			ac.updateConnectivityState(connectivity.TransientFailure, err)
 
 			// Backoff.
 			b := ac.resetBackoff
@@ -1093,6 +1195,7 @@ func (ac *addrConn) resetTransport() {
 // first successful one. It returns the transport, the address and a Event in
 // the successful case. The Event fires when the returned transport disconnects.
 func (ac *addrConn) tryAllAddrs(addrs []resolver.Address, connectDeadline time.Time) (transport.ClientTransport, resolver.Address, *grpcsync.Event, error) {
+	var firstConnErr error
 	for _, addr := range addrs {
 		ac.mu.Lock()
 		if ac.state == connectivity.Shutdown {
@@ -1121,11 +1224,14 @@ func (ac *addrConn) tryAllAddrs(addrs []resolver.Address, connectDeadline time.T
 		if err == nil {
 			return newTr, addr, reconnect, nil
 		}
+		if firstConnErr == nil {
+			firstConnErr = err
+		}
 		ac.cc.blockingpicker.updateConnectionError(err)
 	}
 
 	// Couldn't connect to any address.
-	return nil, resolver.Address{}, nil, fmt.Errorf("couldn't connect to any address")
+	return nil, resolver.Address{}, nil, firstConnErr
 }
 
 // createTransport creates a connection to addr. It returns the transport and a
@@ -1136,10 +1242,16 @@ func (ac *addrConn) createTransport(addr resolver.Address, copts transport.Conne
 	onCloseCalled := make(chan struct{})
 	reconnect := grpcsync.NewEvent()
 
+	authority := ac.cc.authority
+	// addr.ServerName takes precedent over ClientConn authority, if present.
+	if addr.ServerName != "" {
+		authority = addr.ServerName
+	}
+
 	target := transport.TargetInfo{
 		Addr:      addr.Addr,
 		Metadata:  addr.Metadata,
-		Authority: ac.cc.authority,
+		Authority: authority,
 	}
 
 	once := sync.Once{}
@@ -1152,7 +1264,7 @@ func (ac *addrConn) createTransport(addr resolver.Address, copts transport.Conne
 				// state to Connecting.
 				//
 				// TODO: this should be Idle when grpc-go properly supports it.
-				ac.updateConnectivityState(connectivity.Connecting)
+				ac.updateConnectivityState(connectivity.Connecting, nil)
 			}
 		})
 		ac.mu.Unlock()
@@ -1167,7 +1279,7 @@ func (ac *addrConn) createTransport(addr resolver.Address, copts transport.Conne
 				// state to Connecting.
 				//
 				// TODO: this should be Idle when grpc-go properly supports it.
-				ac.updateConnectivityState(connectivity.Connecting)
+				ac.updateConnectivityState(connectivity.Connecting, nil)
 			}
 		})
 		ac.mu.Unlock()
@@ -1193,7 +1305,7 @@ func (ac *addrConn) createTransport(addr resolver.Address, copts transport.Conne
 	}
 
 	select {
-	case <-time.After(connectDeadline.Sub(time.Now())):
+	case <-time.After(time.Until(connectDeadline)):
 		// We didn't get the preface in time.
 		newTr.Close()
 		grpclog.Warningf("grpc: addrConn.createTransport failed to connect to %v: didn't receive server preface in time. Reconnecting...", addr)
@@ -1224,7 +1336,7 @@ func (ac *addrConn) startHealthCheck(ctx context.Context) {
 	var healthcheckManagingState bool
 	defer func() {
 		if !healthcheckManagingState {
-			ac.updateConnectivityState(connectivity.Ready)
+			ac.updateConnectivityState(connectivity.Ready, nil)
 		}
 	}()
 
@@ -1260,13 +1372,13 @@ func (ac *addrConn) startHealthCheck(ctx context.Context) {
 		ac.mu.Unlock()
 		return newNonRetryClientStream(ctx, &StreamDesc{ServerStreams: true}, method, currentTr, ac)
 	}
-	setConnectivityState := func(s connectivity.State) {
+	setConnectivityState := func(s connectivity.State, lastErr error) {
 		ac.mu.Lock()
 		defer ac.mu.Unlock()
 		if ac.transport != currentTr {
 			return
 		}
-		ac.updateConnectivityState(s)
+		ac.updateConnectivityState(s, lastErr)
 	}
 	// Start the health checking stream.
 	go func() {
@@ -1331,8 +1443,8 @@ func (ac *addrConn) tearDown(err error) {
 	curTr := ac.transport
 	ac.transport = nil
 	// We have to set the state to Shutdown before anything else to prevent races
-	// between setting the state and logic that waits on context cancelation / etc.
-	ac.updateConnectivityState(connectivity.Shutdown)
+	// between setting the state and logic that waits on context cancellation / etc.
+	ac.updateConnectivityState(connectivity.Shutdown, nil)
 	ac.cancel()
 	ac.curAddr = resolver.Address{}
 	if err == errConnDrain && curTr != nil {
@@ -1355,7 +1467,7 @@ func (ac *addrConn) tearDown(err error) {
 			},
 		})
 		// TraceEvent needs to be called before RemoveEntry, as TraceEvent may add trace reference to
-		// the entity beng deleted, and thus prevent it from being deleted right away.
+		// the entity being deleted, and thus prevent it from being deleted right away.
 		channelz.RemoveEntry(ac.channelzID)
 	}
 	ac.mu.Unlock()
@@ -1445,3 +1557,12 @@ func (c *channelzChannel) ChannelzMetric() *channelz.ChannelInternalMetric {
 // Deprecated: This error is never returned by grpc and should not be
 // referenced by users.
 var ErrClientConnTimeout = errors.New("grpc: timed out when dialing")
+
+func (cc *ClientConn) getResolver(scheme string) resolver.Builder {
+	for _, rb := range cc.dopts.resolvers {
+		if cc.parsedTarget.Scheme == rb.Scheme() {
+			return rb
+		}
+	}
+	return resolver.Get(cc.parsedTarget.Scheme)
+}