rebase: bump google.golang.org/grpc from 1.59.0 to 1.60.1

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.59.0 to 1.60.1. - [Release notes](https://github.com/grpc/grpc-go/releases) - [Commits](https://github.com/grpc/grpc-go/compare/v1.59.0...v1.60.1) --- updated-dependencies: - dependency-name: google.golang.org/grpc dependency-type: direct:production update-type: version-update:semver-minor ... Signed-off-by: dependabot[bot] <support@github.com>
2025-06-13 18:43:34 +00:00 · 2024-01-04 07:36:42 +00:00
parent c807059618
commit 0ec64b7552
52 changed files with 1970 additions and 1670 deletions
--- a/vendor/google.golang.org/grpc/clientconn.go
+++ b/vendor/google.golang.org/grpc/clientconn.go
@ -33,9 +33,7 @@ import (
 	"google.golang.org/grpc/balancer/base"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/connectivity"
-	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/internal"
-	"google.golang.org/grpc/internal/backoff"
 	"google.golang.org/grpc/internal/channelz"
 	"google.golang.org/grpc/internal/grpcsync"
 	"google.golang.org/grpc/internal/idle"
@ -48,9 +46,9 @@ import (
 	"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.
 	_ "google.golang.org/grpc/internal/resolver/unix"        // To register unix resolver.
+	_ "google.golang.org/grpc/resolver/dns"                  // To register dns resolver.
 )

 const (
@ -119,23 +117,8 @@ func (dcs *defaultConfigSelector) SelectConfig(rpcInfo iresolver.RPCInfo) (*ires
 	}, nil
 }

-// DialContext creates a client connection to the given target. By default, it's
-// a non-blocking dial (the function won't wait for connections to be
-// established, and connecting happens in the background). To make it a blocking
-// dial, use WithBlock() dial option.
-//
-// In the non-blocking case, the ctx does not act against the connection. It
-// only controls the setup steps.
-//
-// In the blocking case, ctx can be used to cancel or expire the pending
-// connection. Once this function returns, the cancellation and expiration of
-// ctx will be noop. Users should call ClientConn.Close to terminate all the
-// pending operations after this function returns.
-//
-// The target name syntax is defined in
-// https://github.com/grpc/grpc/blob/master/doc/naming.md.
-// e.g. to use dns resolver, a "dns:///" prefix should be applied to the target.
-func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *ClientConn, err error) {
+// newClient returns a new client in idle mode.
+func newClient(target string, opts ...DialOption) (conn *ClientConn, err error) {
 	cc := &ClientConn{
 		target: target,
 		conns:  make(map[*addrConn]struct{}),
@ -143,23 +126,11 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 		czData: new(channelzData),
 	}

-	// We start the channel off in idle mode, but kick it out of idle at the end
-	// of this method, instead of waiting for the first RPC. Other gRPC
-	// implementations do wait for the first RPC to kick the channel out of
-	// idle. But doing so would be a major behavior change for our users who are
-	// used to seeing the channel active after Dial.
-	//
-	// Taking this approach of kicking it out of idle at the end of this method
-	// allows us to share the code between channel creation and exiting idle
-	// mode. This will also make it easy for us to switch to starting the
-	// channel off in idle, if at all we ever get to do that.
-	cc.idlenessState = ccIdlenessStateIdle
-
 	cc.retryThrottler.Store((*retryThrottler)(nil))
 	cc.safeConfigSelector.UpdateConfigSelector(&defaultConfigSelector{nil})
 	cc.ctx, cc.cancel = context.WithCancel(context.Background())
-	cc.exitIdleCond = sync.NewCond(&cc.mu)

+	// Apply dial options.
 	disableGlobalOpts := false
 	for _, opt := range opts {
 		if _, ok := opt.(*disableGlobalDialOptions); ok {
@ -177,21 +148,9 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	for _, opt := range opts {
 		opt.apply(&cc.dopts)
 	}
-
 	chainUnaryClientInterceptors(cc)
 	chainStreamClientInterceptors(cc)

-	defer func() {
-		if err != nil {
-			cc.Close()
-		}
-	}()
-
-	// Register ClientConn with channelz.
-	cc.channelzRegistration(target)
-
-	cc.csMgr = newConnectivityStateManager(cc.ctx, cc.channelzID)
-
 	if err := cc.validateTransportCredentials(); err != nil {
 		return nil, err
 	}
@ -205,10 +164,80 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	}
 	cc.mkp = cc.dopts.copts.KeepaliveParams

-	if cc.dopts.copts.UserAgent != "" {
-		cc.dopts.copts.UserAgent += " " + grpcUA
-	} else {
-		cc.dopts.copts.UserAgent = grpcUA
+	// Register ClientConn with channelz.
+	cc.channelzRegistration(target)
+
+	// TODO: Ideally it should be impossible to error from this function after
+	// channelz registration.  This will require removing some channelz logs
+	// from the following functions that can error.  Errors can be returned to
+	// the user, and successful logs can be emitted here, after the checks have
+	// passed and channelz is subsequently registered.
+
+	// Determine the resolver to use.
+	if err := cc.parseTargetAndFindResolver(); err != nil {
+		channelz.RemoveEntry(cc.channelzID)
+		return nil, err
+	}
+	if err = cc.determineAuthority(); err != nil {
+		channelz.RemoveEntry(cc.channelzID)
+		return nil, err
+	}
+
+	cc.csMgr = newConnectivityStateManager(cc.ctx, cc.channelzID)
+	cc.pickerWrapper = newPickerWrapper(cc.dopts.copts.StatsHandlers)
+
+	cc.initIdleStateLocked() // Safe to call without the lock, since nothing else has a reference to cc.
+	cc.idlenessMgr = idle.NewManager((*idler)(cc), cc.dopts.idleTimeout)
+	return cc, nil
+}
+
+// DialContext creates a client connection to the given target. By default, it's
+// a non-blocking dial (the function won't wait for connections to be
+// established, and connecting happens in the background). To make it a blocking
+// dial, use WithBlock() dial option.
+//
+// In the non-blocking case, the ctx does not act against the connection. It
+// only controls the setup steps.
+//
+// In the blocking case, ctx can be used to cancel or expire the pending
+// connection. Once this function returns, the cancellation and expiration of
+// ctx will be noop. Users should call ClientConn.Close to terminate all the
+// pending operations after this function returns.
+//
+// The target name syntax is defined in
+// https://github.com/grpc/grpc/blob/master/doc/naming.md.
+// e.g. to use dns resolver, a "dns:///" prefix should be applied to the target.
+func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *ClientConn, err error) {
+	cc, err := newClient(target, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	// We start the channel off in idle mode, but kick it out of idle now,
+	// instead of waiting for the first RPC. Other gRPC implementations do wait
+	// for the first RPC to kick the channel out of idle. But doing so would be
+	// a major behavior change for our users who are used to seeing the channel
+	// active after Dial.
+	//
+	// Taking this approach of kicking it out of idle at the end of this method
+	// allows us to share the code between channel creation and exiting idle
+	// mode. This will also make it easy for us to switch to starting the
+	// channel off in idle, i.e. by making newClient exported.
+
+	defer func() {
+		if err != nil {
+			cc.Close()
+		}
+	}()
+
+	// This creates the name resolver, load balancer, etc.
+	if err := cc.idlenessMgr.ExitIdleMode(); err != nil {
+		return nil, err
+	}
+
+	// Return now for non-blocking dials.
+	if !cc.dopts.block {
+		return cc, nil
 	}

 	if cc.dopts.timeout > 0 {
@ -231,49 +260,6 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 		}
 	}()

-	if cc.dopts.bs == nil {
-		cc.dopts.bs = backoff.DefaultExponential
-	}
-
-	// Determine the resolver to use.
-	if err := cc.parseTargetAndFindResolver(); err != nil {
-		return nil, err
-	}
-	if err = cc.determineAuthority(); err != nil {
-		return nil, err
-	}
-
-	if cc.dopts.scChan != nil {
-		// Blocking wait for the initial service config.
-		select {
-		case sc, ok := <-cc.dopts.scChan:
-			if ok {
-				cc.sc = &sc
-				cc.safeConfigSelector.UpdateConfigSelector(&defaultConfigSelector{&sc})
-			}
-		case <-ctx.Done():
-			return nil, ctx.Err()
-		}
-	}
-	if cc.dopts.scChan != nil {
-		go cc.scWatcher()
-	}
-
-	// This creates the name resolver, load balancer, blocking picker etc.
-	if err := cc.exitIdleMode(); err != nil {
-		return nil, err
-	}
-
-	// Configure idleness support with configured idle timeout or default idle
-	// timeout duration. Idleness can be explicitly disabled by the user, by
-	// setting the dial option to 0.
-	cc.idlenessMgr = idle.NewManager(idle.ManagerOptions{Enforcer: (*idler)(cc), Timeout: cc.dopts.idleTimeout, Logger: logger})
-
-	// Return early for non-blocking dials.
-	if !cc.dopts.block {
-		return cc, nil
-	}
-
 	// A blocking dial blocks until the clientConn is ready.
 	for {
 		s := cc.GetState()
@ -320,8 +306,8 @@ func (cc *ClientConn) addTraceEvent(msg string) {

 type idler ClientConn

-func (i *idler) EnterIdleMode() error {
-	return (*ClientConn)(i).enterIdleMode()
+func (i *idler) EnterIdleMode() {
+	(*ClientConn)(i).enterIdleMode()
 }

 func (i *idler) ExitIdleMode() error {
@ -329,117 +315,71 @@ func (i *idler) ExitIdleMode() error {
 }

 // exitIdleMode moves the channel out of idle mode by recreating the name
-// resolver and load balancer.
-func (cc *ClientConn) exitIdleMode() error {
+// resolver and load balancer.  This should never be called directly; use
+// cc.idlenessMgr.ExitIdleMode instead.
+func (cc *ClientConn) exitIdleMode() (err error) {
 	cc.mu.Lock()
 	if cc.conns == nil {
 		cc.mu.Unlock()
 		return errConnClosing
 	}
-	if cc.idlenessState != ccIdlenessStateIdle {
-		channelz.Infof(logger, cc.channelzID, "ClientConn asked to exit idle mode, current mode is %v", cc.idlenessState)
-		cc.mu.Unlock()
-		return nil
-	}
-
-	defer func() {
-		// When Close() and exitIdleMode() race against each other, one of the
-		// following two can happen:
-		// - Close() wins the race and runs first. exitIdleMode() runs after, and
-		//   sees that the ClientConn is already closed and hence returns early.
-		// - exitIdleMode() wins the race and runs first and recreates the balancer
-		//   and releases the lock before recreating the resolver. If Close() runs
-		//   in this window, it will wait for exitIdleMode to complete.
-		//
-		// We achieve this synchronization using the below condition variable.
-		cc.mu.Lock()
-		cc.idlenessState = ccIdlenessStateActive
-		cc.exitIdleCond.Signal()
-		cc.mu.Unlock()
-	}()
-
-	cc.idlenessState = ccIdlenessStateExitingIdle
-	exitedIdle := false
-	if cc.blockingpicker == nil {
-		cc.blockingpicker = newPickerWrapper(cc.dopts.copts.StatsHandlers)
-	} else {
-		cc.blockingpicker.exitIdleMode()
-		exitedIdle = true
-	}
-
-	var credsClone credentials.TransportCredentials
-	if creds := cc.dopts.copts.TransportCredentials; creds != nil {
-		credsClone = creds.Clone()
-	}
-	if cc.balancerWrapper == nil {
-		cc.balancerWrapper = newCCBalancerWrapper(cc, balancer.BuildOptions{
-			DialCreds:        credsClone,
-			CredsBundle:      cc.dopts.copts.CredsBundle,
-			Dialer:           cc.dopts.copts.Dialer,
-			Authority:        cc.authority,
-			CustomUserAgent:  cc.dopts.copts.UserAgent,
-			ChannelzParentID: cc.channelzID,
-			Target:           cc.parsedTarget,
-		})
-	} else {
-		cc.balancerWrapper.exitIdleMode()
-	}
-	cc.firstResolveEvent = grpcsync.NewEvent()
 	cc.mu.Unlock()

 	// This needs to be called without cc.mu because this builds a new resolver
-	// which might update state or report error inline which needs to be handled
-	// by cc.updateResolverState() which also grabs cc.mu.
-	if err := cc.initResolverWrapper(credsClone); err != nil {
+	// which might update state or report error inline, which would then need to
+	// acquire cc.mu.
+	if err := cc.resolverWrapper.start(); err != nil {
 		return err
 	}

-	if exitedIdle {
-		cc.addTraceEvent("exiting idle mode")
-	}
+	cc.addTraceEvent("exiting idle mode")
 	return nil
 }

-// enterIdleMode puts the channel in idle mode, and as part of it shuts down the
-// name resolver, load balancer and any subchannels.
-func (cc *ClientConn) enterIdleMode() error {
-	cc.mu.Lock()
-	defer cc.mu.Unlock()
-
-	if cc.conns == nil {
-		return ErrClientConnClosing
-	}
-	if cc.idlenessState != ccIdlenessStateActive {
-		channelz.Warningf(logger, cc.channelzID, "ClientConn asked to enter idle mode, current mode is %v", cc.idlenessState)
-		return nil
-	}
-
+// initIdleStateLocked initializes common state to how it should be while idle.
+func (cc *ClientConn) initIdleStateLocked() {
+	cc.resolverWrapper = newCCResolverWrapper(cc)
+	cc.balancerWrapper = newCCBalancerWrapper(cc)
+	cc.firstResolveEvent = grpcsync.NewEvent()
 	// cc.conns == nil is a proxy for the ClientConn being closed. So, instead
 	// of setting it to nil here, we recreate the map. This also means that we
 	// don't have to do this when exiting idle mode.
-	conns := cc.conns
 	cc.conns = make(map[*addrConn]struct{})
+}

-	// TODO: Currently, we close the resolver wrapper upon entering idle mode
-	// and create a new one upon exiting idle mode. This means that the
-	// `cc.resolverWrapper` field would be overwritten everytime we exit idle
-	// mode. While this means that we need to hold `cc.mu` when accessing
-	// `cc.resolverWrapper`, it makes the code simpler in the wrapper. We should
-	// try to do the same for the balancer and picker wrappers too.
-	cc.resolverWrapper.close()
-	cc.blockingpicker.enterIdleMode()
-	cc.balancerWrapper.enterIdleMode()
+// enterIdleMode puts the channel in idle mode, and as part of it shuts down the
+// name resolver, load balancer, and any subchannels.  This should never be
+// called directly; use cc.idlenessMgr.EnterIdleMode instead.
+func (cc *ClientConn) enterIdleMode() {
+	cc.mu.Lock()
+
+	if cc.conns == nil {
+		cc.mu.Unlock()
+		return
+	}
+
+	conns := cc.conns
+
+	rWrapper := cc.resolverWrapper
+	rWrapper.close()
+	cc.pickerWrapper.reset()
+	bWrapper := cc.balancerWrapper
+	bWrapper.close()
 	cc.csMgr.updateState(connectivity.Idle)
-	cc.idlenessState = ccIdlenessStateIdle
 	cc.addTraceEvent("entering idle mode")

-	go func() {
-		for ac := range conns {
-			ac.tearDown(errConnIdling)
-		}
-	}()
+	cc.initIdleStateLocked()

-	return nil
+	cc.mu.Unlock()
+
+	// Block until the name resolver and LB policy are closed.
+	<-rWrapper.serializer.Done()
+	<-bWrapper.serializer.Done()
+
+	// Close all subchannels after the LB policy is closed.
+	for ac := range conns {
+		ac.tearDown(errConnIdling)
+	}
 }

 // validateTransportCredentials performs a series of checks on the configured
@ -649,66 +589,35 @@ type ClientConn struct {
 	dopts           dialOptions          // Default and user specified dial options.
 	channelzID      *channelz.Identifier // Channelz identifier for the channel.
 	resolverBuilder resolver.Builder     // See parseTargetAndFindResolver().
-	balancerWrapper *ccBalancerWrapper   // Uses gracefulswitch.balancer underneath.
-	idlenessMgr     idle.Manager
+	idlenessMgr     *idle.Manager

 	// The following provide their own synchronization, and therefore don't
 	// require cc.mu to be held to access them.
 	csMgr              *connectivityStateManager
-	blockingpicker     *pickerWrapper
+	pickerWrapper      *pickerWrapper
 	safeConfigSelector iresolver.SafeConfigSelector
 	czData             *channelzData
 	retryThrottler     atomic.Value // Updated from service config.

-	// firstResolveEvent is used to track whether the name resolver sent us at
-	// least one update. RPCs block on this event.
-	firstResolveEvent *grpcsync.Event
-
 	// mu protects the following fields.
 	// TODO: split mu so the same mutex isn't used for everything.
 	mu              sync.RWMutex
-	resolverWrapper *ccResolverWrapper         // Initialized in Dial; cleared in Close.
+	resolverWrapper *ccResolverWrapper         // Always recreated whenever entering idle to simplify Close.
+	balancerWrapper *ccBalancerWrapper         // Always recreated whenever entering idle to simplify Close.
 	sc              *ServiceConfig             // Latest service config received from the resolver.
 	conns           map[*addrConn]struct{}     // Set to nil on close.
 	mkp             keepalive.ClientParameters // May be updated upon receipt of a GoAway.
-	idlenessState   ccIdlenessState            // Tracks idleness state of the channel.
-	exitIdleCond    *sync.Cond                 // Signalled when channel exits idle.
+	// firstResolveEvent is used to track whether the name resolver sent us at
+	// least one update. RPCs block on this event.  May be accessed without mu
+	// if we know we cannot be asked to enter idle mode while accessing it (e.g.
+	// when the idle manager has already been closed, or if we are already
+	// entering idle mode).
+	firstResolveEvent *grpcsync.Event

 	lceMu               sync.Mutex // protects lastConnectionError
 	lastConnectionError error
 }

-// ccIdlenessState tracks the idleness state of the channel.
-//
-// Channels start off in `active` and move to `idle` after a period of
-// inactivity. When moving back to `active` upon an incoming RPC, they
-// transition through `exiting_idle`. This state is useful for synchronization
-// with Close().
-//
-// This state tracking is mostly for self-protection. The idlenessManager is
-// expected to keep track of the state as well, and is expected not to call into
-// the ClientConn unnecessarily.
-type ccIdlenessState int8
-
-const (
-	ccIdlenessStateActive ccIdlenessState = iota
-	ccIdlenessStateIdle
-	ccIdlenessStateExitingIdle
-)
-
-func (s ccIdlenessState) String() string {
-	switch s {
-	case ccIdlenessStateActive:
-		return "active"
-	case ccIdlenessStateIdle:
-		return "idle"
-	case ccIdlenessStateExitingIdle:
-		return "exitingIdle"
-	default:
-		return "unknown"
-	}
-}
-
 // WaitForStateChange waits until the connectivity.State of ClientConn changes from sourceState or
 // ctx expires. A true value is returned in former case and false in latter.
 //
@ -748,29 +657,15 @@ func (cc *ClientConn) GetState() connectivity.State {
 // Notice: This API is EXPERIMENTAL and may be changed or removed in a later
 // release.
 func (cc *ClientConn) Connect() {
-	cc.exitIdleMode()
+	if err := cc.idlenessMgr.ExitIdleMode(); err != nil {
+		cc.addTraceEvent(err.Error())
+		return
+	}
 	// If the ClientConn was not in idle mode, we need to call ExitIdle on the
 	// LB policy so that connections can be created.
-	cc.balancerWrapper.exitIdleMode()
-}
-
-func (cc *ClientConn) scWatcher() {
-	for {
-		select {
-		case sc, ok := <-cc.dopts.scChan:
-			if !ok {
-				return
-			}
-			cc.mu.Lock()
-			// TODO: load balance policy runtime change is ignored.
-			// We may revisit this decision in the future.
-			cc.sc = &sc
-			cc.safeConfigSelector.UpdateConfigSelector(&defaultConfigSelector{&sc})
-			cc.mu.Unlock()
-		case <-cc.ctx.Done():
-			return
-		}
-	}
+	cc.mu.Lock()
+	cc.balancerWrapper.exitIdle()
+	cc.mu.Unlock()
 }

 // waitForResolvedAddrs blocks until the resolver has provided addresses or the
@ -804,11 +699,11 @@ func init() {
 	internal.SubscribeToConnectivityStateChanges = func(cc *ClientConn, s grpcsync.Subscriber) func() {
 		return cc.csMgr.pubSub.Subscribe(s)
 	}
-	internal.EnterIdleModeForTesting = func(cc *ClientConn) error {
-		return cc.enterIdleMode()
+	internal.EnterIdleModeForTesting = func(cc *ClientConn) {
+		cc.idlenessMgr.EnterIdleModeForTesting()
 	}
 	internal.ExitIdleModeForTesting = func(cc *ClientConn) error {
-		return cc.exitIdleMode()
+		return cc.idlenessMgr.ExitIdleMode()
 	}
 }

@ -824,9 +719,8 @@ func (cc *ClientConn) maybeApplyDefaultServiceConfig(addrs []resolver.Address) {
 	}
 }

-func (cc *ClientConn) updateResolverState(s resolver.State, err error) error {
+func (cc *ClientConn) updateResolverStateAndUnlock(s resolver.State, err error) error {
 	defer cc.firstResolveEvent.Fire()
-	cc.mu.Lock()
 	// 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.
@ -872,7 +766,7 @@ func (cc *ClientConn) updateResolverState(s resolver.State, err error) error {
 			if cc.sc == nil {
 				// Apply the failing LB only if we haven't received valid service config
 				// from the name resolver in the past.
-				cc.applyFailingLB(s.ServiceConfig)
+				cc.applyFailingLBLocked(s.ServiceConfig)
 				cc.mu.Unlock()
 				return ret
 			}
@ -894,15 +788,13 @@ func (cc *ClientConn) updateResolverState(s resolver.State, err error) error {
 	return ret
 }

-// applyFailingLB is akin to configuring an LB policy on the channel which
+// applyFailingLBLocked is akin to configuring an LB policy on the channel which
 // always fails RPCs. Here, an actual LB policy is not configured, but an always
 // erroring picker is configured, which returns errors with information about
 // what was invalid in the received service config. A config selector with no
 // service config is configured, and the connectivity state of the channel is
 // set to TransientFailure.
-//
-// Caller must hold cc.mu.
-func (cc *ClientConn) applyFailingLB(sc *serviceconfig.ParseResult) {
+func (cc *ClientConn) applyFailingLBLocked(sc *serviceconfig.ParseResult) {
 	var err error
 	if sc.Err != nil {
 		err = status.Errorf(codes.Unavailable, "error parsing service config: %v", sc.Err)
@ -910,14 +802,10 @@ func (cc *ClientConn) applyFailingLB(sc *serviceconfig.ParseResult) {
 		err = status.Errorf(codes.Unavailable, "illegal service config type: %T", sc.Config)
 	}
 	cc.safeConfigSelector.UpdateConfigSelector(&defaultConfigSelector{nil})
-	cc.blockingpicker.updatePicker(base.NewErrPicker(err))
+	cc.pickerWrapper.updatePicker(base.NewErrPicker(err))
 	cc.csMgr.updateState(connectivity.TransientFailure)
 }

-func (cc *ClientConn) handleSubConnStateChange(sc balancer.SubConn, s connectivity.State, err error) {
-	cc.balancerWrapper.updateSubConnState(sc, s, err)
-}
-
 // Makes a copy of the input addresses slice and clears out the balancer
 // attributes field. Addresses are passed during subconn creation and address
 // update operations. In both cases, we will clear the balancer attributes by
@ -932,10 +820,14 @@ func copyAddressesWithoutBalancerAttributes(in []resolver.Address) []resolver.Ad
 	return out
 }

-// newAddrConn creates an addrConn for addrs and adds it to cc.conns.
+// newAddrConnLocked creates an addrConn for addrs and adds it to cc.conns.
 //
 // Caller needs to make sure len(addrs) > 0.
-func (cc *ClientConn) newAddrConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (*addrConn, error) {
+func (cc *ClientConn) newAddrConnLocked(addrs []resolver.Address, opts balancer.NewSubConnOptions) (*addrConn, error) {
+	if cc.conns == nil {
+		return nil, ErrClientConnClosing
+	}
+
 	ac := &addrConn{
 		state:        connectivity.Idle,
 		cc:           cc,
@ -947,12 +839,6 @@ func (cc *ClientConn) newAddrConn(addrs []resolver.Address, opts balancer.NewSub
 		stateChan:    make(chan struct{}),
 	}
 	ac.ctx, ac.cancel = context.WithCancel(cc.ctx)
-	// Track ac in cc. This needs to be done before any getTransport(...) is called.
-	cc.mu.Lock()
-	defer cc.mu.Unlock()
-	if cc.conns == nil {
-		return nil, ErrClientConnClosing
-	}

 	var err error
 	ac.channelzID, err = channelz.RegisterSubChannel(ac, cc.channelzID, "")
@ -968,6 +854,7 @@ func (cc *ClientConn) newAddrConn(addrs []resolver.Address, opts balancer.NewSub
 		},
 	})

+	// Track ac in cc. This needs to be done before any getTransport(...) is called.
 	cc.conns[ac] = struct{}{}
 	return ac, nil
 }
@ -1174,7 +1061,7 @@ func (cc *ClientConn) healthCheckConfig() *healthCheckConfig {
 }

 func (cc *ClientConn) getTransport(ctx context.Context, failfast bool, method string) (transport.ClientTransport, balancer.PickResult, error) {
-	return cc.blockingpicker.pick(ctx, failfast, balancer.PickInfo{
+	return cc.pickerWrapper.pick(ctx, failfast, balancer.PickInfo{
 		Ctx:            ctx,
 		FullMethodName: method,
 	})
@ -1216,12 +1103,12 @@ func (cc *ClientConn) applyServiceConfigAndBalancer(sc *ServiceConfig, configSel

 func (cc *ClientConn) resolveNow(o resolver.ResolveNowOptions) {
 	cc.mu.RLock()
-	r := cc.resolverWrapper
+	cc.resolverWrapper.resolveNow(o)
 	cc.mu.RUnlock()
-	if r == nil {
-		return
-	}
-	go r.resolveNow(o)
+}
+
+func (cc *ClientConn) resolveNowLocked(o resolver.ResolveNowOptions) {
+	cc.resolverWrapper.resolveNow(o)
 }

 // ResetConnectBackoff wakes up all subchannels in transient failure and causes
@ -1253,40 +1140,32 @@ func (cc *ClientConn) Close() error {
 		<-cc.csMgr.pubSub.Done()
 	}()

+	// Prevent calls to enter/exit idle immediately, and ensure we are not
+	// currently entering/exiting idle mode.
+	cc.idlenessMgr.Close()
+
 	cc.mu.Lock()
 	if cc.conns == nil {
 		cc.mu.Unlock()
 		return ErrClientConnClosing
 	}

-	for cc.idlenessState == ccIdlenessStateExitingIdle {
-		cc.exitIdleCond.Wait()
-	}
-
 	conns := cc.conns
 	cc.conns = nil
 	cc.csMgr.updateState(connectivity.Shutdown)

-	pWrapper := cc.blockingpicker
-	rWrapper := cc.resolverWrapper
-	bWrapper := cc.balancerWrapper
-	idlenessMgr := cc.idlenessMgr
+	// We can safely unlock and continue to access all fields now as
+	// cc.conns==nil, preventing any further operations on cc.
 	cc.mu.Unlock()

+	cc.resolverWrapper.close()
 	// The order of closing matters here since the balancer wrapper assumes the
 	// picker is closed before it is closed.
-	if pWrapper != nil {
-		pWrapper.close()
-	}
-	if bWrapper != nil {
-		bWrapper.close()
-	}
-	if rWrapper != nil {
-		rWrapper.close()
-	}
-	if idlenessMgr != nil {
-		idlenessMgr.Close()
-	}
+	cc.pickerWrapper.close()
+	cc.balancerWrapper.close()
+
+	<-cc.resolverWrapper.serializer.Done()
+	<-cc.balancerWrapper.serializer.Done()

 	for ac := range conns {
 		ac.tearDown(ErrClientConnClosing)
@ -1307,7 +1186,7 @@ type addrConn struct {

 	cc     *ClientConn
 	dopts  dialOptions
-	acbw   balancer.SubConn
+	acbw   *acBalancerWrapper
 	scopts balancer.NewSubConnOptions

 	// transport is set when there's a viable transport (note: ac state may not be READY as LB channel
@ -1345,7 +1224,7 @@ func (ac *addrConn) updateConnectivityState(s connectivity.State, lastErr error)
 	} else {
 		channelz.Infof(logger, ac.channelzID, "Subchannel Connectivity change to %v, last error: %s", s, lastErr)
 	}
-	ac.cc.handleSubConnStateChange(ac.acbw, s, lastErr)
+	ac.acbw.updateState(s, lastErr)
 }

 // adjustParams updates parameters used to create transports upon
@ -1849,7 +1728,7 @@ func (cc *ClientConn) parseTargetAndFindResolver() error {
 	if err != nil {
 		channelz.Infof(logger, cc.channelzID, "dial target %q parse failed: %v", cc.target, err)
 	} else {
-		channelz.Infof(logger, cc.channelzID, "parsed dial target is: %+v", parsedTarget)
+		channelz.Infof(logger, cc.channelzID, "parsed dial target is: %#v", parsedTarget)
 		rb = cc.getResolver(parsedTarget.URL.Scheme)
 		if rb != nil {
 			cc.parsedTarget = parsedTarget
@ -2007,32 +1886,3 @@ func (cc *ClientConn) determineAuthority() error {
 	channelz.Infof(logger, cc.channelzID, "Channel authority set to %q", cc.authority)
 	return nil
 }
-
-// initResolverWrapper creates a ccResolverWrapper, which builds the name
-// resolver. This method grabs the lock to assign the newly built resolver
-// wrapper to the cc.resolverWrapper field.
-func (cc *ClientConn) initResolverWrapper(creds credentials.TransportCredentials) error {
-	rw, err := newCCResolverWrapper(cc, ccResolverWrapperOpts{
-		target:  cc.parsedTarget,
-		builder: cc.resolverBuilder,
-		bOpts: resolver.BuildOptions{
-			DisableServiceConfig: cc.dopts.disableServiceConfig,
-			DialCreds:            creds,
-			CredsBundle:          cc.dopts.copts.CredsBundle,
-			Dialer:               cc.dopts.copts.Dialer,
-		},
-		channelzID: cc.channelzID,
-	})
-	if err != nil {
-		return fmt.Errorf("failed to build resolver: %v", err)
-	}
-	// Resolver implementations may report state update or error inline when
-	// built (or right after), and this is handled in cc.updateResolverState.
-	// Also, an error from the resolver might lead to a re-resolution request
-	// from the balancer, which is handled in resolveNow() where
-	// `cc.resolverWrapper` is accessed. Hence, we need to hold the lock here.
-	cc.mu.Lock()
-	cc.resolverWrapper = rw
-	cc.mu.Unlock()
-	return nil
-}