TUN-3375: Upgrade coredns and prometheus dependencies

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

@@ -111,12 +111,24 @@ type NewSubConnOptions struct {
 	// CredsBundle is the credentials bundle that will be used in the created
 	// SubConn. If it's nil, the original creds from grpc DialOptions will be
 	// used.
+	//
+	// Deprecated: Use the Attributes field in resolver.Address to pass
+	// arbitrary data to the credential handshaker.
 	CredsBundle credentials.Bundle
 	// HealthCheckEnabled indicates whether health check service should be
 	// enabled on this SubConn
 	HealthCheckEnabled bool
 }
 
+// State contains the balancer's state relevant to the gRPC ClientConn.
+type State struct {
+	// State contains the connectivity state of the balancer, which is used to
+	// determine the state of the ClientConn.
+	ConnectivityState connectivity.State
+	// Picker is used to choose connections (SubConns) for RPCs.
+	Picker Picker
+}
+
 // ClientConn represents a gRPC ClientConn.
 //
 // This interface is to be implemented by gRPC. Users should not need a
@@ -132,15 +144,15 @@ type ClientConn interface {
 	// The SubConn will be shutdown.
 	RemoveSubConn(SubConn)
 
-	// UpdateBalancerState is called by balancer to notify gRPC that some internal
-	// state in balancer has changed.
+	// UpdateState notifies gRPC that the balancer's internal state has
+	// changed.
 	//
-	// gRPC will update the connectivity state of the ClientConn, and will call pick
-	// on the new picker to pick new SubConn.
-	UpdateBalancerState(s connectivity.State, p Picker)
+	// gRPC will update the connectivity state of the ClientConn, and will call
+	// Pick on the new Picker to pick new SubConns.
+	UpdateState(State)
 
 	// ResolveNow is called by balancer to notify gRPC to do a name resolving.
-	ResolveNow(resolver.ResolveNowOption)
+	ResolveNow(resolver.ResolveNowOptions)
 
 	// Target returns the dial target for this ClientConn.
 	//
@@ -185,11 +197,14 @@ type ConfigParser interface {
 	ParseConfig(LoadBalancingConfigJSON json.RawMessage) (serviceconfig.LoadBalancingConfig, error)
 }
 
-// PickOptions contains addition information for the Pick operation.
-type PickOptions struct {
+// PickInfo contains additional information for the Pick operation.
+type PickInfo struct {
 	// FullMethodName is the method name that NewClientStream() is called
 	// with. The canonical format is /service/Method.
 	FullMethodName string
+	// Ctx is the RPC's context, and may contain relevant RPC-level information
+	// like the outgoing header metadata.
+	Ctx context.Context
 }
 
 // DoneInfo contains additional information for done.
@@ -211,50 +226,65 @@ type DoneInfo struct {
 
 var (
 	// ErrNoSubConnAvailable indicates no SubConn is available for pick().
-	// gRPC will block the RPC until a new picker is available via UpdateBalancerState().
+	// gRPC will block the RPC until a new picker is available via UpdateState().
 	ErrNoSubConnAvailable = errors.New("no SubConn is available")
 	// ErrTransientFailure indicates all SubConns are in TransientFailure.
 	// WaitForReady RPCs will block, non-WaitForReady RPCs will fail.
+	//
+	// Deprecated: return an appropriate error based on the last resolution or
+	// connection attempt instead.  The behavior is the same for any non-gRPC
+	// status error.
 	ErrTransientFailure = errors.New("all SubConns are in TransientFailure")
 )
 
+// PickResult contains information related to a connection chosen for an RPC.
+type PickResult struct {
+	// SubConn is the connection to use for this pick, if its state is Ready.
+	// If the state is not Ready, gRPC will block the RPC until a new Picker is
+	// provided by the balancer (using ClientConn.UpdateState).  The SubConn
+	// must be one returned by ClientConn.NewSubConn.
+	SubConn SubConn
+
+	// Done is called when the RPC is completed.  If the SubConn is not ready,
+	// this will be called with a nil parameter.  If the SubConn is not a valid
+	// type, Done may not be called.  May be nil if the balancer does not wish
+	// to be notified when the RPC completes.
+	Done func(DoneInfo)
+}
+
+// TransientFailureError returns e.  It exists for backward compatibility and
+// will be deleted soon.
+//
+// Deprecated: no longer necessary, picker errors are treated this way by
+// default.
+func TransientFailureError(e error) error { return e }
+
 // Picker is used by gRPC to pick a SubConn to send an RPC.
 // Balancer is expected to generate a new picker from its snapshot every time its
 // internal state has changed.
 //
-// The pickers used by gRPC can be updated by ClientConn.UpdateBalancerState().
+// The pickers used by gRPC can be updated by ClientConn.UpdateState().
 type Picker interface {
-	// Pick returns the SubConn to be used to send the RPC.
-	// The returned SubConn must be one returned by NewSubConn().
+	// Pick returns the connection to use for this RPC and related information.
 	//
-	// This functions is expected to return:
-	// - a SubConn that is known to be READY;
-	// - ErrNoSubConnAvailable if no SubConn is available, but progress is being
-	//   made (for example, some SubConn is in CONNECTING mode);
-	// - other errors if no active connecting is happening (for example, all SubConn
-	//   are in TRANSIENT_FAILURE mode).
+	// Pick should not block.  If the balancer needs to do I/O or any blocking
+	// or time-consuming work to service this call, it should return
+	// ErrNoSubConnAvailable, and the Pick call will be repeated by gRPC when
+	// the Picker is updated (using ClientConn.UpdateState).
 	//
-	// If a SubConn is returned:
-	// - If it is READY, gRPC will send the RPC on it;
-	// - If it is not ready, or becomes not ready after it's returned, gRPC will
-	//   block until UpdateBalancerState() is called and will call pick on the
-	//   new picker. The done function returned from Pick(), if not nil, will be
-	//   called with nil error, no bytes sent and no bytes received.
+	// If an error is returned:
 	//
-	// If the returned error is not nil:
-	// - If the error is ErrNoSubConnAvailable, gRPC will block until UpdateBalancerState()
-	// - If the error is ErrTransientFailure:
-	//   - If the RPC is wait-for-ready, gRPC will block until UpdateBalancerState()
-	//     is called to pick again;
-	//   - Otherwise, RPC will fail with unavailable error.
-	// - Else (error is other non-nil error):
-	//   - The RPC will fail with unavailable error.
+	// - If the error is ErrNoSubConnAvailable, gRPC will block until a new
+	//   Picker is provided by the balancer (using ClientConn.UpdateState).
 	//
-	// The returned done() function will be called once the rpc has finished,
-	// with the final status of that RPC.  If the SubConn returned is not a
-	// valid SubConn type, done may not be called.  done may be nil if balancer
-	// doesn't care about the RPC status.
-	Pick(ctx context.Context, opts PickOptions) (conn SubConn, done func(DoneInfo), err error)
+	// - If the error is a status error (implemented by the grpc/status
+	//   package), gRPC will terminate the RPC with the code and message
+	//   provided.
+	//
+	// - For all other errors, wait for ready RPCs will wait, but non-wait for
+	//   ready RPCs will be terminated with this error's Error() string and
+	//   status code Unavailable.
+	Pick(info PickInfo) (PickResult, error)
 }
 
 // Balancer takes input from gRPC, manages SubConns, and collects and aggregates
@@ -262,29 +292,21 @@ type Picker interface {
 //
 // It also generates and updates the Picker used by gRPC to pick SubConns for RPCs.
 //
-// HandleSubConnectionStateChange, HandleResolvedAddrs and Close are guaranteed
-// to be called synchronously from the same goroutine.
-// There's no guarantee on picker.Pick, it may be called anytime.
+// UpdateClientConnState, ResolverError, UpdateSubConnState, and Close are
+// guaranteed to be called synchronously from the same goroutine.  There's no
+// guarantee on picker.Pick, it may be called anytime.
 type Balancer interface {
-	// HandleSubConnStateChange is called by gRPC when the connectivity state
-	// of sc has changed.
-	// Balancer is expected to aggregate all the state of SubConn and report
-	// that back to gRPC.
-	// Balancer should also generate and update Pickers when its internal state has
-	// been changed by the new state.
-	//
-	// Deprecated: if V2Balancer is implemented by the Balancer,
-	// UpdateSubConnState will be called instead.
-	HandleSubConnStateChange(sc SubConn, state connectivity.State)
-	// HandleResolvedAddrs is called by gRPC to send updated resolved addresses to
-	// balancers.
-	// Balancer can create new SubConn or remove SubConn with the addresses.
-	// An empty address slice and a non-nil error will be passed if the resolver returns
-	// non-nil error to gRPC.
-	//
-	// Deprecated: if V2Balancer is implemented by the Balancer,
-	// UpdateClientConnState will be called instead.
-	HandleResolvedAddrs([]resolver.Address, error)
+	// UpdateClientConnState is called by gRPC when the state of the ClientConn
+	// changes.  If the error returned is ErrBadResolverState, the ClientConn
+	// will begin calling ResolveNow on the active name resolver with
+	// exponential backoff until a subsequent call to UpdateClientConnState
+	// returns a nil error.  Any other errors are currently ignored.
+	UpdateClientConnState(ClientConnState) error
+	// ResolverError is called by gRPC when the name resolver reports an error.
+	ResolverError(error)
+	// UpdateSubConnState is called by gRPC when the state of a SubConn
+	// changes.
+	UpdateSubConnState(SubConn, SubConnState)
 	// Close closes the balancer. The balancer is not required to call
 	// ClientConn.RemoveSubConn for its existing SubConns.
 	Close()
@@ -292,8 +314,11 @@ type Balancer interface {
 
 // SubConnState describes the state of a SubConn.
 type SubConnState struct {
+	// ConnectivityState is the connectivity state of the SubConn.
 	ConnectivityState connectivity.State
-	// TODO: add last connection error
+	// ConnectionError is set if the ConnectivityState is TransientFailure,
+	// describing the reason the SubConn failed.  Otherwise, it is nil.
+	ConnectionError error
 }
 
 // ClientConnState describes the state of a ClientConn relevant to the
@@ -305,30 +330,17 @@ type ClientConnState struct {
 	BalancerConfig serviceconfig.LoadBalancingConfig
 }
 
-// V2Balancer is defined for documentation purposes.  If a Balancer also
-// implements V2Balancer, its UpdateClientConnState method will be called
-// instead of HandleResolvedAddrs and its UpdateSubConnState will be called
-// instead of HandleSubConnStateChange.
-type V2Balancer interface {
-	// UpdateClientConnState is called by gRPC when the state of the ClientConn
-	// changes.
-	UpdateClientConnState(ClientConnState)
-	// UpdateSubConnState is called by gRPC when the state of a SubConn
-	// changes.
-	UpdateSubConnState(SubConn, SubConnState)
-	// Close closes the balancer. The balancer is not required to call
-	// ClientConn.RemoveSubConn for its existing SubConns.
-	Close()
-}
+// ErrBadResolverState may be returned by UpdateClientConnState to indicate a
+// problem with the provided name resolver data.
+var ErrBadResolverState = errors.New("bad resolver state")
 
 // ConnectivityStateEvaluator takes the connectivity states of multiple SubConns
 // and returns one aggregated connectivity state.
 //
 // It's not thread safe.
 type ConnectivityStateEvaluator struct {
-	numReady            uint64 // Number of addrConns in ready state.
-	numConnecting       uint64 // Number of addrConns in connecting state.
-	numTransientFailure uint64 // Number of addrConns in transientFailure.
+	numReady      uint64 // Number of addrConns in ready state.
+	numConnecting uint64 // Number of addrConns in connecting state.
 }
 
 // RecordTransition records state change happening in subConn and based on that
@@ -348,8 +360,6 @@ func (cse *ConnectivityStateEvaluator) RecordTransition(oldState, newState conne
 			cse.numReady += updateVal
 		case connectivity.Connecting:
 			cse.numConnecting += updateVal
-		case connectivity.TransientFailure:
-			cse.numTransientFailure += updateVal
 		}
 	}
 

vendor/google.golang.org/grpc/balancer/base/balancer.go

@@ -19,7 +19,8 @@
 package base
 
 import (
-	"context"
+	"errors"
+	"fmt"
 
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/connectivity"
@@ -27,6 +28,8 @@ import (
 	"google.golang.org/grpc/resolver"
 )
 
+var logger = grpclog.Component("balancer")
+
 type baseBuilder struct {
 	name          string
 	pickerBuilder PickerBuilder
@@ -34,19 +37,20 @@ type baseBuilder struct {
 }
 
 func (bb *baseBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
-	return &baseBalancer{
+	bal := &baseBalancer{
 		cc:            cc,
 		pickerBuilder: bb.pickerBuilder,
 
 		subConns: make(map[resolver.Address]balancer.SubConn),
 		scStates: make(map[balancer.SubConn]connectivity.State),
 		csEvltr:  &balancer.ConnectivityStateEvaluator{},
-		// Initialize picker to a picker that always return
-		// ErrNoSubConnAvailable, because when state of a SubConn changes, we
-		// may call UpdateBalancerState with this picker.
-		picker: NewErrPicker(balancer.ErrNoSubConnAvailable),
-		config: bb.config,
+		config:   bb.config,
 	}
+	// Initialize picker to a picker that always returns
+	// ErrNoSubConnAvailable, because when state of a SubConn changes, we
+	// may call UpdateState with this picker.
+	bal.picker = NewErrPicker(balancer.ErrNoSubConnAvailable)
+	return bal
 }
 
 func (bb *baseBuilder) Name() string {
@@ -64,18 +68,36 @@ type baseBalancer struct {
 	scStates map[balancer.SubConn]connectivity.State
 	picker   balancer.Picker
 	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) {
-	panic("not implemented")
-}
-
-func (b *baseBalancer) UpdateClientConnState(s balancer.ClientConnState) {
-	// TODO: handle s.ResolverState.Err (log if not nil) once implemented.
-	// TODO: handle s.ResolverState.ServiceConfig?
-	if grpclog.V(2) {
-		grpclog.Infoln("base.baseBalancer: got new ClientConn state: ", s)
+func (b *baseBalancer) ResolverError(err error) {
+	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()
+	b.cc.UpdateState(balancer.State{
+		ConnectivityState: b.state,
+		Picker:            b.picker,
+	})
+}
+
+func (b *baseBalancer) UpdateClientConnState(s balancer.ClientConnState) error {
+	// TODO: handle s.ResolverState.ServiceConfig?
+	if logger.V(2) {
+		logger.Info("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 {
@@ -84,7 +106,7 @@ func (b *baseBalancer) UpdateClientConnState(s balancer.ClientConnState) {
 			// a is a new address (not existing in b.subConns).
 			sc, err := b.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{HealthCheckEnabled: b.config.HealthCheck})
 			if err != nil {
-				grpclog.Warningf("base.baseBalancer: failed to create new SubConn: %v", err)
+				logger.Warningf("base.baseBalancer: failed to create new SubConn: %v", err)
 				continue
 			}
 			b.subConns[a] = sc
@@ -98,47 +120,72 @@ func (b *baseBalancer) UpdateClientConnState(s balancer.ClientConnState) {
 			b.cc.RemoveSubConn(sc)
 			delete(b.subConns, a)
 			// Keep the state of this sc in b.scStates until sc's state becomes Shutdown.
-			// The entry will be deleted in HandleSubConnStateChange.
+			// The entry will be deleted in UpdateSubConnState.
 		}
 	}
+	// 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() {
 	if b.state == connectivity.TransientFailure {
-		b.picker = NewErrPicker(balancer.ErrTransientFailure)
+		b.picker = NewErrPicker(b.mergeErrors())
 		return
 	}
-	readySCs := make(map[resolver.Address]balancer.SubConn)
+	readySCs := make(map[balancer.SubConn]SubConnInfo)
 
 	// Filter out all ready SCs from full subConn map.
 	for addr, sc := range b.subConns {
 		if st, ok := b.scStates[sc]; ok && st == connectivity.Ready {
-			readySCs[addr] = sc
+			readySCs[sc] = SubConnInfo{Address: addr}
 		}
 	}
-	b.picker = b.pickerBuilder.Build(readySCs)
-}
-
-func (b *baseBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
-	panic("not implemented")
+	b.picker = b.pickerBuilder.Build(PickerBuildInfo{ReadySCs: readySCs})
 }
 
 func (b *baseBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
 	s := state.ConnectivityState
-	if grpclog.V(2) {
-		grpclog.Infof("base.baseBalancer: handle SubConn state change: %p, %v", sc, s)
+	if logger.V(2) {
+		logger.Infof("base.baseBalancer: handle SubConn state change: %p, %v", sc, s)
 	}
 	oldS, ok := b.scStates[sc]
 	if !ok {
-		if grpclog.V(2) {
-			grpclog.Infof("base.baseBalancer: got state changes for an unknown SubConn: %p, %v", sc, s)
+		if logger.V(2) {
+			logger.Infof("base.baseBalancer: got state changes for an unknown SubConn: %p, %v", sc, s)
 		}
 		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:
@@ -147,22 +194,23 @@ func (b *baseBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.Su
 		// 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.state == connectivity.TransientFailure {
 		b.regeneratePicker()
 	}
 
-	b.cc.UpdateBalancerState(b.state, b.picker)
+	b.cc.UpdateState(balancer.State{ConnectivityState: b.state, Picker: b.picker})
 }
 
 // Close is a nop because base balancer doesn't have internal state to clean up,
@@ -170,15 +218,20 @@ func (b *baseBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.Su
 func (b *baseBalancer) Close() {
 }
 
-// NewErrPicker returns a picker that always returns err on Pick().
+// NewErrPicker returns a Picker that always returns err on Pick().
 func NewErrPicker(err error) balancer.Picker {
 	return &errPicker{err: err}
 }
 
+// NewErrPickerV2 is temporarily defined for backward compatibility reasons.
+//
+// Deprecated: use NewErrPicker instead.
+var NewErrPickerV2 = NewErrPicker
+
 type errPicker struct {
 	err error // Pick() always returns this err.
 }
 
-func (p *errPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
-	return nil, nil, p.err
+func (p *errPicker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
+	return balancer.PickResult{}, p.err
 }

vendor/google.golang.org/grpc/balancer/base/base.go

@@ -37,15 +37,22 @@ import (
 
 // PickerBuilder creates balancer.Picker.
 type PickerBuilder interface {
-	// Build takes a slice of ready SubConns, and returns a picker that will be
-	// used by gRPC to pick a SubConn.
-	Build(readySCs map[resolver.Address]balancer.SubConn) balancer.Picker
+	// Build returns a picker that will be used by gRPC to pick a SubConn.
+	Build(info PickerBuildInfo) balancer.Picker
 }
 
-// NewBalancerBuilder returns a balancer builder. The balancers
-// built by this builder will use the picker builder to build pickers.
-func NewBalancerBuilder(name string, pb PickerBuilder) balancer.Builder {
-	return NewBalancerBuilderWithConfig(name, pb, Config{})
+// PickerBuildInfo contains information needed by the picker builder to
+// construct a picker.
+type PickerBuildInfo struct {
+	// ReadySCs is a map from all ready SubConns to the Addresses used to
+	// create them.
+	ReadySCs map[balancer.SubConn]SubConnInfo
+}
+
+// SubConnInfo contains information about a SubConn created by the base
+// balancer.
+type SubConnInfo struct {
+	Address resolver.Address // the address used to create this SubConn
 }
 
 // Config contains the config info about the base balancer builder.
@@ -54,8 +61,8 @@ type Config struct {
 	HealthCheck bool
 }
 
-// NewBalancerBuilderWithConfig returns a base balancer builder configured by the provided config.
-func NewBalancerBuilderWithConfig(name string, pb PickerBuilder, config Config) balancer.Builder {
+// NewBalancerBuilder returns a base balancer builder configured by the provided config.
+func NewBalancerBuilder(name string, pb PickerBuilder, config Config) balancer.Builder {
 	return &baseBuilder{
 		name:          name,
 		pickerBuilder: pb,

vendor/google.golang.org/grpc/balancer/grpclb/state/state.go

@@ -0,0 +1,51 @@
+/*
+ *
+ * Copyright 2020 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package state declares grpclb types to be set by resolvers wishing to pass
+// information to grpclb via resolver.State Attributes.
+package state
+
+import (
+	"google.golang.org/grpc/resolver"
+)
+
+// keyType is the key to use for storing State in Attributes.
+type keyType string
+
+const key = keyType("grpc.grpclb.state")
+
+// State contains gRPCLB-relevant data passed from the name resolver.
+type State struct {
+	// BalancerAddresses contains the remote load balancer address(es).  If
+	// set, overrides any resolver-provided addresses with Type of GRPCLB.
+	BalancerAddresses []resolver.Address
+}
+
+// Set returns a copy of the provided state with attributes containing s.  s's
+// data should not be mutated after calling Set.
+func Set(state resolver.State, s *State) resolver.State {
+	state.Attributes = state.Attributes.WithValues(key, s)
+	return state
+}
+
+// Get returns the grpclb State in the resolver.State, or nil if not present.
+// The returned data should not be mutated.
+func Get(state resolver.State) *State {
+	s, _ := state.Attributes.Value(key).(*State)
+	return s
+}

vendor/google.golang.org/grpc/balancer/roundrobin/roundrobin.go

@@ -22,22 +22,22 @@
 package roundrobin
 
 import (
-	"context"
 	"sync"
 
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/balancer/base"
 	"google.golang.org/grpc/grpclog"
 	"google.golang.org/grpc/internal/grpcrand"
-	"google.golang.org/grpc/resolver"
 )
 
 // Name is the name of round_robin balancer.
 const Name = "round_robin"
 
+var logger = grpclog.Component("roundrobin")
+
 // newBuilder creates a new roundrobin balancer builder.
 func newBuilder() balancer.Builder {
-	return base.NewBalancerBuilderWithConfig(Name, &rrPickerBuilder{}, base.Config{HealthCheck: true})
+	return base.NewBalancerBuilder(Name, &rrPickerBuilder{}, base.Config{HealthCheck: true})
 }
 
 func init() {
@@ -46,13 +46,13 @@ func init() {
 
 type rrPickerBuilder struct{}
 
-func (*rrPickerBuilder) Build(readySCs map[resolver.Address]balancer.SubConn) balancer.Picker {
-	grpclog.Infof("roundrobinPicker: newPicker called with readySCs: %v", readySCs)
-	if len(readySCs) == 0 {
+func (*rrPickerBuilder) Build(info base.PickerBuildInfo) balancer.Picker {
+	logger.Infof("roundrobinPicker: newPicker called with info: %v", info)
+	if len(info.ReadySCs) == 0 {
 		return base.NewErrPicker(balancer.ErrNoSubConnAvailable)
 	}
 	var scs []balancer.SubConn
-	for _, sc := range readySCs {
+	for sc := range info.ReadySCs {
 		scs = append(scs, sc)
 	}
 	return &rrPicker{
@@ -74,10 +74,10 @@ type rrPicker struct {
 	next int
 }
 
-func (p *rrPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+func (p *rrPicker) Pick(balancer.PickInfo) (balancer.PickResult, error) {
 	p.mu.Lock()
 	sc := p.subConns[p.next]
 	p.next = (p.next + 1) % len(p.subConns)
 	p.mu.Unlock()
-	return sc, nil, nil
+	return balancer.PickResult{SubConn: sc}, nil
 }