Initial checkin from CRI-O repo

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

1 files changed, 888 insertions, 0 deletions

diff --git a/vendor/google.golang.org/grpc/clientconn.go b/vendor/google.golang.org/grpc/clientconn.go
new file mode 100644
index 000000000..61674729a
--- /dev/null
+++ b/vendor/google.golang.org/grpc/clientconn.go
@@ -0,0 +1,888 @@
+/*
+ *
+ * Copyright 2014, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package grpc
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/trace"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/transport"
+)
+
+var (
+	// ErrClientConnClosing indicates that the operation is illegal because
+	// the ClientConn is closing.
+	ErrClientConnClosing = errors.New("grpc: the client connection is closing")
+	// ErrClientConnTimeout indicates that the ClientConn cannot establish the
+	// underlying connections within the specified timeout.
+	ErrClientConnTimeout = errors.New("grpc: timed out when dialing")
+
+	// errNoTransportSecurity indicates that there is no transport security
+	// being set for ClientConn. Users should either set one or explicitly
+	// call WithInsecure DialOption to disable security.
+	errNoTransportSecurity = errors.New("grpc: no transport security set (use grpc.WithInsecure() explicitly or set credentials)")
+	// errTransportCredentialsMissing indicates that users want to transmit security
+	// information (e.g., oauth2 token) which requires secure connection on an insecure
+	// connection.
+	errTransportCredentialsMissing = errors.New("grpc: the credentials require transport level security (use grpc.WithTransportCredentials() to set)")
+	// errCredentialsConflict indicates that grpc.WithTransportCredentials()
+	// and grpc.WithInsecure() are both called for a connection.
+	errCredentialsConflict = errors.New("grpc: transport credentials are set for an insecure connection (grpc.WithTransportCredentials() and grpc.WithInsecure() are both called)")
+	// errNetworkIO indicates that the connection is down due to some network I/O error.
+	errNetworkIO = errors.New("grpc: failed with network I/O error")
+	// errConnDrain indicates that the connection starts to be drained and does not accept any new RPCs.
+	errConnDrain = errors.New("grpc: the connection is drained")
+	// errConnClosing indicates that the connection is closing.
+	errConnClosing = errors.New("grpc: the connection is closing")
+	// 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
+)
+
+// dialOptions configure a Dial call. dialOptions are set by the DialOption
+// values passed to Dial.
+type dialOptions struct {
+	unaryInt  UnaryClientInterceptor
+	streamInt StreamClientInterceptor
+	codec     Codec
+	cp        Compressor
+	dc        Decompressor
+	bs        backoffStrategy
+	balancer  Balancer
+	block     bool
+	insecure  bool
+	timeout   time.Duration
+	copts     transport.ConnectOptions
+}
+
+// DialOption configures how we set up the connection.
+type DialOption func(*dialOptions)
+
+// WithCodec returns a DialOption which sets a codec for message marshaling and unmarshaling.
+func WithCodec(c Codec) DialOption {
+	return func(o *dialOptions) {
+		o.codec = c
+	}
+}
+
+// WithCompressor returns a DialOption which sets a CompressorGenerator for generating message
+// compressor.
+func WithCompressor(cp Compressor) DialOption {
+	return func(o *dialOptions) {
+		o.cp = cp
+	}
+}
+
+// WithDecompressor returns a DialOption which sets a DecompressorGenerator for generating
+// message decompressor.
+func WithDecompressor(dc Decompressor) DialOption {
+	return func(o *dialOptions) {
+		o.dc = dc
+	}
+}
+
+// WithBalancer returns a DialOption which sets a load balancer.
+func WithBalancer(b Balancer) DialOption {
+	return func(o *dialOptions) {
+		o.balancer = b
+	}
+}
+
+// WithBackoffMaxDelay configures the dialer to use the provided maximum delay
+// when backing off after failed connection attempts.
+func WithBackoffMaxDelay(md time.Duration) DialOption {
+	return WithBackoffConfig(BackoffConfig{MaxDelay: md})
+}
+
+// WithBackoffConfig configures the dialer to use the provided backoff
+// parameters after connection failures.
+//
+// Use WithBackoffMaxDelay until more parameters on BackoffConfig are opened up
+// for use.
+func WithBackoffConfig(b BackoffConfig) DialOption {
+	// Set defaults to ensure that provided BackoffConfig is valid and
+	// unexported fields get default values.
+	setDefaults(&b)
+	return withBackoff(b)
+}
+
+// withBackoff sets the backoff strategy used for retries after a
+// failed connection attempt.
+//
+// This can be exported if arbitrary backoff strategies are allowed by gRPC.
+func withBackoff(bs backoffStrategy) DialOption {
+	return func(o *dialOptions) {
+		o.bs = bs
+	}
+}
+
+// WithBlock returns a DialOption which makes caller of Dial blocks until the underlying
+// connection is up. Without this, Dial returns immediately and connecting the server
+// happens in background.
+func WithBlock() DialOption {
+	return func(o *dialOptions) {
+		o.block = true
+	}
+}
+
+// WithInsecure returns a DialOption which disables transport security for this ClientConn.
+// Note that transport security is required unless WithInsecure is set.
+func WithInsecure() DialOption {
+	return func(o *dialOptions) {
+		o.insecure = true
+	}
+}
+
+// WithTransportCredentials returns a DialOption which configures a
+// connection level security credentials (e.g., TLS/SSL).
+func WithTransportCredentials(creds credentials.TransportCredentials) DialOption {
+	return func(o *dialOptions) {
+		o.copts.TransportCredentials = creds
+	}
+}
+
+// WithPerRPCCredentials returns a DialOption which sets
+// credentials which will place auth state on each outbound RPC.
+func WithPerRPCCredentials(creds credentials.PerRPCCredentials) DialOption {
+	return func(o *dialOptions) {
+		o.copts.PerRPCCredentials = append(o.copts.PerRPCCredentials, creds)
+	}
+}
+
+// WithTimeout returns a DialOption that configures a timeout for dialing a ClientConn
+// initially. This is valid if and only if WithBlock() is present.
+func WithTimeout(d time.Duration) DialOption {
+	return func(o *dialOptions) {
+		o.timeout = d
+	}
+}
+
+// WithDialer returns a DialOption that specifies a function to use for dialing network addresses.
+func WithDialer(f func(string, time.Duration) (net.Conn, error)) DialOption {
+	return func(o *dialOptions) {
+		o.copts.Dialer = func(ctx context.Context, addr string) (net.Conn, error) {
+			if deadline, ok := ctx.Deadline(); ok {
+				return f(addr, deadline.Sub(time.Now()))
+			}
+			return f(addr, 0)
+		}
+	}
+}
+
+// WithUserAgent returns a DialOption that specifies a user agent string for all the RPCs.
+func WithUserAgent(s string) DialOption {
+	return func(o *dialOptions) {
+		o.copts.UserAgent = s
+	}
+}
+
+// WithUnaryInterceptor returns a DialOption that specifies the interceptor for unary RPCs.
+func WithUnaryInterceptor(f UnaryClientInterceptor) DialOption {
+	return func(o *dialOptions) {
+		o.unaryInt = f
+	}
+}
+
+// WithStreamInterceptor returns a DialOption that specifies the interceptor for streaming RPCs.
+func WithStreamInterceptor(f StreamClientInterceptor) DialOption {
+	return func(o *dialOptions) {
+		o.streamInt = f
+	}
+}
+
+// Dial creates a client connection to the given target.
+func Dial(target string, opts ...DialOption) (*ClientConn, error) {
+	return DialContext(context.Background(), target, opts...)
+}
+
+// DialContext creates a client connection to the given target. ctx can be used to
+// cancel or expire the pending connecting. 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.
+// This is the EXPERIMENTAL API.
+func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *ClientConn, err error) {
+	cc := &ClientConn{
+		target: target,
+		conns:  make(map[Address]*addrConn),
+	}
+	cc.ctx, cc.cancel = context.WithCancel(context.Background())
+	defer func() {
+		select {
+		case <-ctx.Done():
+			conn, err = nil, ctx.Err()
+		default:
+		}
+
+		if err != nil {
+			cc.Close()
+		}
+	}()
+
+	for _, opt := range opts {
+		opt(&cc.dopts)
+	}
+
+	// Set defaults.
+	if cc.dopts.codec == nil {
+		cc.dopts.codec = protoCodec{}
+	}
+	if cc.dopts.bs == nil {
+		cc.dopts.bs = DefaultBackoffConfig
+	}
+	creds := cc.dopts.copts.TransportCredentials
+	if creds != nil && creds.Info().ServerName != "" {
+		cc.authority = creds.Info().ServerName
+	} else {
+		colonPos := strings.LastIndex(target, ":")
+		if colonPos == -1 {
+			colonPos = len(target)
+		}
+		cc.authority = target[:colonPos]
+	}
+	var ok bool
+	waitC := make(chan error, 1)
+	go func() {
+		var addrs []Address
+		if cc.dopts.balancer == nil {
+			// Connect to target directly if balancer is nil.
+			addrs = append(addrs, Address{Addr: target})
+		} else {
+			var credsClone credentials.TransportCredentials
+			if creds != nil {
+				credsClone = creds.Clone()
+			}
+			config := BalancerConfig{
+				DialCreds: credsClone,
+			}
+			if err := cc.dopts.balancer.Start(target, config); err != nil {
+				waitC <- err
+				return
+			}
+			ch := cc.dopts.balancer.Notify()
+			if ch == nil {
+				// There is no name resolver installed.
+				addrs = append(addrs, Address{Addr: target})
+			} else {
+				addrs, ok = <-ch
+				if !ok || len(addrs) == 0 {
+					waitC <- errNoAddr
+					return
+				}
+			}
+		}
+		for _, a := range addrs {
+			if err := cc.resetAddrConn(a, false, nil); err != nil {
+				waitC <- err
+				return
+			}
+		}
+		close(waitC)
+	}()
+	var timeoutCh <-chan time.Time
+	if cc.dopts.timeout > 0 {
+		timeoutCh = time.After(cc.dopts.timeout)
+	}
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	case err := <-waitC:
+		if err != nil {
+			return nil, err
+		}
+	case <-timeoutCh:
+		return nil, ErrClientConnTimeout
+	}
+	// If balancer is nil or balancer.Notify() is nil, ok will be false here.
+	// The lbWatcher goroutine will not be created.
+	if ok {
+		go cc.lbWatcher()
+	}
+	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 started shutting down.
+	Shutdown
+)
+
+func (s ConnectivityState) String() string {
+	switch s {
+	case Idle:
+		return "IDLE"
+	case Connecting:
+		return "CONNECTING"
+	case Ready:
+		return "READY"
+	case TransientFailure:
+		return "TRANSIENT_FAILURE"
+	case Shutdown:
+		return "SHUTDOWN"
+	default:
+		panic(fmt.Sprintf("unknown connectivity state: %d", s))
+	}
+}
+
+// ClientConn represents a client connection to an RPC server.
+type ClientConn struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	target    string
+	authority string
+	dopts     dialOptions
+
+	mu    sync.RWMutex
+	conns map[Address]*addrConn
+}
+
+func (cc *ClientConn) lbWatcher() {
+	for addrs := range cc.dopts.balancer.Notify() {
+		var (
+			add []Address   // Addresses need to setup connections.
+			del []*addrConn // Connections need to tear down.
+		)
+		cc.mu.Lock()
+		for _, a := range addrs {
+			if _, ok := cc.conns[a]; !ok {
+				add = append(add, a)
+			}
+		}
+		for k, c := range cc.conns {
+			var keep bool
+			for _, a := range addrs {
+				if k == a {
+					keep = true
+					break
+				}
+			}
+			if !keep {
+				del = append(del, c)
+				delete(cc.conns, c.addr)
+			}
+		}
+		cc.mu.Unlock()
+		for _, a := range add {
+			cc.resetAddrConn(a, true, nil)
+		}
+		for _, c := range del {
+			c.tearDown(errConnDrain)
+		}
+	}
+}
+
+// resetAddrConn creates an addrConn for addr and adds it to cc.conns.
+// If there is an old addrConn for addr, it will be torn down, using tearDownErr as the reason.
+// If tearDownErr is nil, errConnDrain will be used instead.
+func (cc *ClientConn) resetAddrConn(addr Address, skipWait bool, tearDownErr error) error {
+	ac := &addrConn{
+		cc:    cc,
+		addr:  addr,
+		dopts: cc.dopts,
+	}
+	ac.ctx, ac.cancel = context.WithCancel(cc.ctx)
+	ac.stateCV = sync.NewCond(&ac.mu)
+	if EnableTracing {
+		ac.events = trace.NewEventLog("grpc.ClientConn", ac.addr.Addr)
+	}
+	if !ac.dopts.insecure {
+		if ac.dopts.copts.TransportCredentials == nil {
+			return errNoTransportSecurity
+		}
+	} else {
+		if ac.dopts.copts.TransportCredentials != nil {
+			return errCredentialsConflict
+		}
+		for _, cd := range ac.dopts.copts.PerRPCCredentials {
+			if cd.RequireTransportSecurity() {
+				return errTransportCredentialsMissing
+			}
+		}
+	}
+	// Track ac in cc. This needs to be done before any getTransport(...) is called.
+	cc.mu.Lock()
+	if cc.conns == nil {
+		cc.mu.Unlock()
+		return ErrClientConnClosing
+	}
+	stale := cc.conns[ac.addr]
+	cc.conns[ac.addr] = ac
+	cc.mu.Unlock()
+	if stale != nil {
+		// There is an addrConn alive on ac.addr already. This could be due to
+		// 1) a buggy Balancer notifies duplicated Addresses;
+		// 2) goaway was received, a new ac will replace the old ac.
+		//    The old ac should be deleted from cc.conns, but the
+		//    underlying transport should drain rather than close.
+		if tearDownErr == nil {
+			// tearDownErr is nil if resetAddrConn is called by
+			// 1) Dial
+			// 2) lbWatcher
+			// In both cases, the stale ac should drain, not close.
+			stale.tearDown(errConnDrain)
+		} else {
+			stale.tearDown(tearDownErr)
+		}
+	}
+	// skipWait may overwrite the decision in ac.dopts.block.
+	if ac.dopts.block && !skipWait {
+		if err := ac.resetTransport(false); err != nil {
+			if err != errConnClosing {
+				// Tear down ac and delete it from cc.conns.
+				cc.mu.Lock()
+				delete(cc.conns, ac.addr)
+				cc.mu.Unlock()
+				ac.tearDown(err)
+			}
+			if e, ok := err.(transport.ConnectionError); ok && !e.Temporary() {
+				return e.Origin()
+			}
+			return err
+		}
+		// Start to monitor the error status of transport.
+		go ac.transportMonitor()
+	} else {
+		// Start a goroutine connecting to the server asynchronously.
+		go func() {
+			if err := ac.resetTransport(false); err != nil {
+				grpclog.Printf("Failed to dial %s: %v; please retry.", ac.addr.Addr, err)
+				if err != errConnClosing {
+					// Keep this ac in cc.conns, to get the reason it's torn down.
+					ac.tearDown(err)
+				}
+				return
+			}
+			ac.transportMonitor()
+		}()
+	}
+	return nil
+}
+
+func (cc *ClientConn) getTransport(ctx context.Context, opts BalancerGetOptions) (transport.ClientTransport, func(), error) {
+	var (
+		ac  *addrConn
+		ok  bool
+		put func()
+	)
+	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
+			break
+		}
+		cc.mu.RUnlock()
+	} else {
+		var (
+			addr Address
+			err  error
+		)
+		addr, put, err = cc.dopts.balancer.Get(ctx, opts)
+		if err != nil {
+			return nil, nil, toRPCErr(err)
+		}
+		cc.mu.RLock()
+		if cc.conns == nil {
+			cc.mu.RUnlock()
+			return nil, nil, toRPCErr(ErrClientConnClosing)
+		}
+		ac, ok = cc.conns[addr]
+		cc.mu.RUnlock()
+	}
+	if !ok {
+		if put != nil {
+			put()
+		}
+		return nil, nil, errConnClosing
+	}
+	t, err := ac.wait(ctx, cc.dopts.balancer != nil, !opts.BlockingWait)
+	if err != nil {
+		if put != nil {
+			put()
+		}
+		return nil, nil, err
+	}
+	return t, put, nil
+}
+
+// Close tears down the ClientConn and all underlying connections.
+func (cc *ClientConn) Close() error {
+	cc.cancel()
+
+	cc.mu.Lock()
+	if cc.conns == nil {
+		cc.mu.Unlock()
+		return ErrClientConnClosing
+	}
+	conns := cc.conns
+	cc.conns = nil
+	cc.mu.Unlock()
+	if cc.dopts.balancer != nil {
+		cc.dopts.balancer.Close()
+	}
+	for _, ac := range conns {
+		ac.tearDown(ErrClientConnClosing)
+	}
+	return nil
+}
+
+// addrConn is a network connection to a given address.
+type addrConn struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	cc     *ClientConn
+	addr   Address
+	dopts  dialOptions
+	events trace.EventLog
+
+	mu      sync.Mutex
+	state   ConnectivityState
+	stateCV *sync.Cond
+	down    func(error) // the handler called when a connection is down.
+	// ready is closed and becomes nil when a new transport is up or failed
+	// due to timeout.
+	ready     chan struct{}
+	transport transport.ClientTransport
+
+	// The reason this addrConn is torn down.
+	tearDownErr error
+}
+
+// printf records an event in ac's event log, unless ac has been closed.
+// REQUIRES ac.mu is held.
+func (ac *addrConn) printf(format string, a ...interface{}) {
+	if ac.events != nil {
+		ac.events.Printf(format, a...)
+	}
+}
+
+// errorf records an error in ac's event log, unless ac has been closed.
+// REQUIRES ac.mu is held.
+func (ac *addrConn) errorf(format string, a ...interface{}) {
+	if ac.events != nil {
+		ac.events.Errorf(format, a...)
+	}
+}
+
+// getState returns the connectivity state of the Conn
+func (ac *addrConn) getState() ConnectivityState {
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	return ac.state
+}
+
+// waitForStateChange blocks until the state changes to something other than the sourceState.
+func (ac *addrConn) waitForStateChange(ctx context.Context, sourceState ConnectivityState) (ConnectivityState, error) {
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	if sourceState != ac.state {
+		return ac.state, nil
+	}
+	done := make(chan struct{})
+	var err error
+	go func() {
+		select {
+		case <-ctx.Done():
+			ac.mu.Lock()
+			err = ctx.Err()
+			ac.stateCV.Broadcast()
+			ac.mu.Unlock()
+		case <-done:
+		}
+	}()
+	defer close(done)
+	for sourceState == ac.state {
+		ac.stateCV.Wait()
+		if err != nil {
+			return ac.state, err
+		}
+	}
+	return ac.state, nil
+}
+
+func (ac *addrConn) resetTransport(closeTransport bool) error {
+	for retries := 0; ; retries++ {
+		ac.mu.Lock()
+		ac.printf("connecting")
+		if ac.state == Shutdown {
+			// ac.tearDown(...) has been invoked.
+			ac.mu.Unlock()
+			return errConnClosing
+		}
+		if ac.down != nil {
+			ac.down(downErrorf(false, true, "%v", errNetworkIO))
+			ac.down = nil
+		}
+		ac.state = Connecting
+		ac.stateCV.Broadcast()
+		t := ac.transport
+		ac.mu.Unlock()
+		if closeTransport && t != nil {
+			t.Close()
+		}
+		sleepTime := ac.dopts.bs.backoff(retries)
+		timeout := minConnectTimeout
+		if timeout < sleepTime {
+			timeout = sleepTime
+		}
+		ctx, cancel := context.WithTimeout(ac.ctx, timeout)
+		connectTime := time.Now()
+		sinfo := transport.TargetInfo{
+			Addr:     ac.addr.Addr,
+			Metadata: ac.addr.Metadata,
+		}
+		newTransport, err := transport.NewClientTransport(ctx, sinfo, ac.dopts.copts)
+		if err != nil {
+			cancel()
+
+			if e, ok := err.(transport.ConnectionError); ok && !e.Temporary() {
+				return err
+			}
+			grpclog.Printf("grpc: addrConn.resetTransport failed to create client transport: %v; Reconnecting to %v", err, ac.addr)
+			ac.mu.Lock()
+			if ac.state == Shutdown {
+				// ac.tearDown(...) has been invoked.
+				ac.mu.Unlock()
+				return errConnClosing
+			}
+			ac.errorf("transient failure: %v", err)
+			ac.state = TransientFailure
+			ac.stateCV.Broadcast()
+			if ac.ready != nil {
+				close(ac.ready)
+				ac.ready = nil
+			}
+			ac.mu.Unlock()
+			closeTransport = false
+			select {
+			case <-time.After(sleepTime - time.Since(connectTime)):
+			case <-ac.ctx.Done():
+				return ac.ctx.Err()
+			}
+			continue
+		}
+		ac.mu.Lock()
+		ac.printf("ready")
+		if ac.state == Shutdown {
+			// ac.tearDown(...) has been invoked.
+			ac.mu.Unlock()
+			newTransport.Close()
+			return errConnClosing
+		}
+		ac.state = Ready
+		ac.stateCV.Broadcast()
+		ac.transport = newTransport
+		if ac.ready != nil {
+			close(ac.ready)
+			ac.ready = nil
+		}
+		if ac.cc.dopts.balancer != nil {
+			ac.down = ac.cc.dopts.balancer.Up(ac.addr)
+		}
+		ac.mu.Unlock()
+		return nil
+	}
+}
+
+// Run in a goroutine to track the error in transport and create the
+// new transport if an error happens. It returns when the channel is closing.
+func (ac *addrConn) transportMonitor() {
+	for {
+		ac.mu.Lock()
+		t := ac.transport
+		ac.mu.Unlock()
+		select {
+		// This is needed to detect the teardown when
+		// the addrConn is idle (i.e., no RPC in flight).
+		case <-ac.ctx.Done():
+			select {
+			case <-t.Error():
+				t.Close()
+			default:
+			}
+			return
+		case <-t.GoAway():
+			// If GoAway happens without any network I/O error, ac is closed without shutting down the
+			// underlying transport (the transport will be closed when all the pending RPCs finished or
+			// failed.).
+			// If GoAway and some network I/O error happen concurrently, ac and its underlying transport
+			// are closed.
+			// In both cases, a new ac is created.
+			select {
+			case <-t.Error():
+				ac.cc.resetAddrConn(ac.addr, true, errNetworkIO)
+			default:
+				ac.cc.resetAddrConn(ac.addr, true, errConnDrain)
+			}
+			return
+		case <-t.Error():
+			select {
+			case <-ac.ctx.Done():
+				t.Close()
+				return
+			case <-t.GoAway():
+				ac.cc.resetAddrConn(ac.addr, true, errNetworkIO)
+				return
+			default:
+			}
+			ac.mu.Lock()
+			if ac.state == Shutdown {
+				// ac has been shutdown.
+				ac.mu.Unlock()
+				return
+			}
+			ac.state = TransientFailure
+			ac.stateCV.Broadcast()
+			ac.mu.Unlock()
+			if err := ac.resetTransport(true); err != nil {
+				ac.mu.Lock()
+				ac.printf("transport exiting: %v", err)
+				ac.mu.Unlock()
+				grpclog.Printf("grpc: addrConn.transportMonitor exits due to: %v", err)
+				if err != errConnClosing {
+					// Keep this ac in cc.conns, to get the reason it's torn down.
+					ac.tearDown(err)
+				}
+				return
+			}
+		}
+	}
+}
+
+// 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 there is a 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:
+			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, errConnClosing
+		case ac.state == Ready:
+			ct := ac.transport
+			ac.mu.Unlock()
+			return ct, nil
+		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:
+		}
+	}
+}
+
+// tearDown starts to tear down the addrConn.
+// TODO(zhaoq): Make this synchronous to avoid unbounded memory consumption in
+// some edge cases (e.g., the caller opens and closes many addrConn's in a
+// tight loop.
+// tearDown doesn't remove ac from ac.cc.conns.
+func (ac *addrConn) tearDown(err error) {
+	ac.cancel()
+
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	if ac.down != nil {
+		ac.down(downErrorf(false, false, "%v", err))
+		ac.down = nil
+	}
+	if err == errConnDrain && ac.transport != nil {
+		// GracefulClose(...) may be executed multiple times when
+		// i) receiving multiple GoAway frames from the server; or
+		// ii) there are concurrent name resolver/Balancer triggered
+		// address removal and GoAway.
+		ac.transport.GracefulClose()
+	}
+	if ac.state == Shutdown {
+		return
+	}
+	ac.state = Shutdown
+	ac.tearDownErr = err
+	ac.stateCV.Broadcast()
+	if ac.events != nil {
+		ac.events.Finish()
+		ac.events = nil
+	}
+	if ac.ready != nil {
+		close(ac.ready)
+		ac.ready = nil
+	}
+	if ac.transport != nil && err != errConnDrain {
+		ac.transport.Close()
+	}
+	return
+}