diff --git a/vendor/google.golang.org/grpc/balancer/base/balancer.go b/vendor/google.golang.org/grpc/balancer/base/balancer.go
index d952f09..80559b8 100644
--- a/vendor/google.golang.org/grpc/balancer/base/balancer.go
+++ b/vendor/google.golang.org/grpc/balancer/base/balancer.go
@@ -21,6 +21,7 @@
 import (
 	"context"
 	"errors"
+	"fmt"
 
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/connectivity"
@@ -76,6 +77,9 @@
 	picker   balancer.Picker
 	v2Picker balancer.V2Picker
 	config   Config
+
+	resolverErr error // the last error reported by the resolver; cleared on successful resolution
+	connErr     error // the last connection error; cleared upon leaving TransientFailure
 }
 
 func (b *baseBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
@@ -83,13 +87,23 @@
 }
 
 func (b *baseBalancer) ResolverError(err error) {
-	switch b.state {
-	case connectivity.TransientFailure, connectivity.Idle, connectivity.Connecting:
-		if b.picker != nil {
-			b.picker = NewErrPicker(err)
-		} else {
-			b.v2Picker = NewErrPickerV2(err)
-		}
+	b.resolverErr = err
+	if len(b.subConns) == 0 {
+		b.state = connectivity.TransientFailure
+	}
+	if b.state != connectivity.TransientFailure {
+		// The picker will not change since the balancer does not currently
+		// report an error.
+		return
+	}
+	b.regeneratePicker()
+	if b.picker != nil {
+		b.cc.UpdateBalancerState(b.state, b.picker)
+	} else {
+		b.cc.UpdateState(balancer.State{
+			ConnectivityState: b.state,
+			Picker:            b.v2Picker,
+		})
 	}
 }
 
@@ -99,6 +113,8 @@
 	if grpclog.V(2) {
 		grpclog.Infoln("base.baseBalancer: got new ClientConn state: ", s)
 	}
+	// Successful resolution; clear resolver error and ensure we return nil.
+	b.resolverErr = nil
 	// addrsSet is the set converted from addrs, it's used for quick lookup of an address.
 	addrsSet := make(map[resolver.Address]struct{})
 	for _, a := range s.ResolverState.Addresses {
@@ -124,27 +140,41 @@
 			// The entry will be deleted in HandleSubConnStateChange.
 		}
 	}
+	// If resolver state contains no addresses, return an error so ClientConn
+	// will trigger re-resolve. Also records this as an resolver error, so when
+	// the overall state turns transient failure, the error message will have
+	// the zero address information.
+	if len(s.ResolverState.Addresses) == 0 {
+		b.ResolverError(errors.New("produced zero addresses"))
+		return balancer.ErrBadResolverState
+	}
 	return nil
 }
 
+// mergeErrors builds an error from the last connection error and the last
+// resolver error.  Must only be called if b.state is TransientFailure.
+func (b *baseBalancer) mergeErrors() error {
+	// connErr must always be non-nil unless there are no SubConns, in which
+	// case resolverErr must be non-nil.
+	if b.connErr == nil {
+		return fmt.Errorf("last resolver error: %v", b.resolverErr)
+	}
+	if b.resolverErr == nil {
+		return fmt.Errorf("last connection error: %v", b.connErr)
+	}
+	return fmt.Errorf("last connection error: %v; last resolver error: %v", b.connErr, b.resolverErr)
+}
+
 // regeneratePicker takes a snapshot of the balancer, and generates a picker
 // from it. The picker is
-//  - errPicker with ErrTransientFailure if the balancer is in TransientFailure,
+//  - errPicker if the balancer is in TransientFailure,
 //  - built by the pickerBuilder with all READY SubConns otherwise.
-func (b *baseBalancer) regeneratePicker(err error) {
+func (b *baseBalancer) regeneratePicker() {
 	if b.state == connectivity.TransientFailure {
 		if b.pickerBuilder != nil {
 			b.picker = NewErrPicker(balancer.ErrTransientFailure)
 		} else {
-			if err != nil {
-				b.v2Picker = NewErrPickerV2(balancer.TransientFailureError(err))
-			} else {
-				// This means the last subchannel transition was not to
-				// TransientFailure (otherwise err must be set), but the
-				// aggregate state of the balancer is TransientFailure, meaning
-				// there are no other addresses.
-				b.v2Picker = NewErrPickerV2(balancer.TransientFailureError(errors.New("resolver returned no addresses")))
-			}
+			b.v2Picker = NewErrPickerV2(balancer.TransientFailureError(b.mergeErrors()))
 		}
 		return
 	}
@@ -187,6 +217,12 @@
 		}
 		return
 	}
+	if oldS == connectivity.TransientFailure && s == connectivity.Connecting {
+		// Once a subconn enters TRANSIENT_FAILURE, ignore subsequent
+		// CONNECTING transitions to prevent the aggregated state from being
+		// always CONNECTING when many backends exist but are all down.
+		return
+	}
 	b.scStates[sc] = s
 	switch s {
 	case connectivity.Idle:
@@ -195,19 +231,20 @@
 		// When an address was removed by resolver, b called RemoveSubConn but
 		// kept the sc's state in scStates. Remove state for this sc here.
 		delete(b.scStates, sc)
+	case connectivity.TransientFailure:
+		// Save error to be reported via picker.
+		b.connErr = state.ConnectionError
 	}
 
-	oldAggrState := b.state
 	b.state = b.csEvltr.RecordTransition(oldS, s)
 
 	// Regenerate picker when one of the following happens:
-	//  - this sc became ready from not-ready
-	//  - this sc became not-ready from ready
-	//  - the aggregated state of balancer became TransientFailure from non-TransientFailure
-	//  - the aggregated state of balancer became non-TransientFailure from TransientFailure
+	//  - this sc entered or left ready
+	//  - the aggregated state of balancer is TransientFailure
+	//    (may need to update error message)
 	if (s == connectivity.Ready) != (oldS == connectivity.Ready) ||
-		(b.state == connectivity.TransientFailure) != (oldAggrState == connectivity.TransientFailure) {
-		b.regeneratePicker(state.ConnectionError)
+		b.state == connectivity.TransientFailure {
+		b.regeneratePicker()
 	}
 
 	if b.picker != nil {