initial add - go fmt on grpc
Change-Id: Ib0afadd2fe5571d1456a091f94f5644458f7d3f4
diff --git a/vendor/google.golang.org/grpc/balancer/balancer.go b/vendor/google.golang.org/grpc/balancer/balancer.go
new file mode 100644
index 0000000..c266f4e
--- /dev/null
+++ b/vendor/google.golang.org/grpc/balancer/balancer.go
@@ -0,0 +1,364 @@
+/*
+ *
+ * Copyright 2017 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 balancer defines APIs for load balancing in gRPC.
+// All APIs in this package are experimental.
+package balancer
+
+import (
+ "context"
+ "encoding/json"
+ "errors"
+ "net"
+ "strings"
+
+ "google.golang.org/grpc/connectivity"
+ "google.golang.org/grpc/credentials"
+ "google.golang.org/grpc/internal"
+ "google.golang.org/grpc/metadata"
+ "google.golang.org/grpc/resolver"
+ "google.golang.org/grpc/serviceconfig"
+)
+
+var (
+ // m is a map from name to balancer builder.
+ m = make(map[string]Builder)
+)
+
+// Register registers the balancer builder to the balancer map. b.Name
+// (lowercased) will be used as the name registered with this builder. If the
+// Builder implements ConfigParser, ParseConfig will be called when new service
+// configs are received by the resolver, and the result will be provided to the
+// Balancer in UpdateClientConnState.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. If multiple Balancers are
+// registered with the same name, the one registered last will take effect.
+func Register(b Builder) {
+ m[strings.ToLower(b.Name())] = b
+}
+
+// unregisterForTesting deletes the balancer with the given name from the
+// balancer map.
+//
+// This function is not thread-safe.
+func unregisterForTesting(name string) {
+ delete(m, name)
+}
+
+func init() {
+ internal.BalancerUnregister = unregisterForTesting
+}
+
+// Get returns the resolver builder registered with the given name.
+// Note that the compare is done in a case-insensitive fashion.
+// If no builder is register with the name, nil will be returned.
+func Get(name string) Builder {
+ if b, ok := m[strings.ToLower(name)]; ok {
+ return b
+ }
+ return nil
+}
+
+// SubConn represents a gRPC sub connection.
+// Each sub connection contains a list of addresses. gRPC will
+// try to connect to them (in sequence), and stop trying the
+// remainder once one connection is successful.
+//
+// The reconnect backoff will be applied on the list, not a single address.
+// For example, try_on_all_addresses -> backoff -> try_on_all_addresses.
+//
+// All SubConns start in IDLE, and will not try to connect. To trigger
+// the connecting, Balancers must call Connect.
+// When the connection encounters an error, it will reconnect immediately.
+// When the connection becomes IDLE, it will not reconnect unless Connect is
+// called.
+//
+// This interface is to be implemented by gRPC. Users should not need a
+// brand new implementation of this interface. For the situations like
+// testing, the new implementation should embed this interface. This allows
+// gRPC to add new methods to this interface.
+type SubConn interface {
+ // UpdateAddresses updates the addresses used in this SubConn.
+ // gRPC checks if currently-connected address is still in the new list.
+ // If it's in the list, the connection will be kept.
+ // If it's not in the list, the connection will gracefully closed, and
+ // a new connection will be created.
+ //
+ // This will trigger a state transition for the SubConn.
+ UpdateAddresses([]resolver.Address)
+ // Connect starts the connecting for this SubConn.
+ Connect()
+}
+
+// NewSubConnOptions contains options to create new SubConn.
+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.
+ CredsBundle credentials.Bundle
+ // HealthCheckEnabled indicates whether health check service should be
+ // enabled on this SubConn
+ HealthCheckEnabled bool
+}
+
+// ClientConn represents a gRPC ClientConn.
+//
+// This interface is to be implemented by gRPC. Users should not need a
+// brand new implementation of this interface. For the situations like
+// testing, the new implementation should embed this interface. This allows
+// gRPC to add new methods to this interface.
+type ClientConn interface {
+ // NewSubConn is called by balancer to create a new SubConn.
+ // It doesn't block and wait for the connections to be established.
+ // Behaviors of the SubConn can be controlled by options.
+ NewSubConn([]resolver.Address, NewSubConnOptions) (SubConn, error)
+ // RemoveSubConn removes the SubConn from ClientConn.
+ // The SubConn will be shutdown.
+ RemoveSubConn(SubConn)
+
+ // UpdateBalancerState is called by balancer to notify gRPC that some internal
+ // state in balancer 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)
+
+ // ResolveNow is called by balancer to notify gRPC to do a name resolving.
+ ResolveNow(resolver.ResolveNowOption)
+
+ // Target returns the dial target for this ClientConn.
+ //
+ // Deprecated: Use the Target field in the BuildOptions instead.
+ Target() string
+}
+
+// BuildOptions contains additional information for Build.
+type BuildOptions struct {
+ // DialCreds is the transport credential the Balancer implementation can
+ // use to dial to a remote load balancer server. The Balancer implementations
+ // can ignore this if it does not need to talk to another party securely.
+ DialCreds credentials.TransportCredentials
+ // CredsBundle is the credentials bundle that the Balancer can use.
+ CredsBundle credentials.Bundle
+ // Dialer is the custom dialer the Balancer implementation can use to dial
+ // to a remote load balancer server. The Balancer implementations
+ // can ignore this if it doesn't need to talk to remote balancer.
+ Dialer func(context.Context, string) (net.Conn, error)
+ // ChannelzParentID is the entity parent's channelz unique identification number.
+ ChannelzParentID int64
+ // Target contains the parsed address info of the dial target. It is the same resolver.Target as
+ // passed to the resolver.
+ // See the documentation for the resolver.Target type for details about what it contains.
+ Target resolver.Target
+}
+
+// Builder creates a balancer.
+type Builder interface {
+ // Build creates a new balancer with the ClientConn.
+ Build(cc ClientConn, opts BuildOptions) Balancer
+ // Name returns the name of balancers built by this builder.
+ // It will be used to pick balancers (for example in service config).
+ Name() string
+}
+
+// ConfigParser parses load balancer configs.
+type ConfigParser interface {
+ // ParseConfig parses the JSON load balancer config provided into an
+ // internal form or returns an error if the config is invalid. For future
+ // compatibility reasons, unknown fields in the config should be ignored.
+ ParseConfig(LoadBalancingConfigJSON json.RawMessage) (serviceconfig.LoadBalancingConfig, error)
+}
+
+// PickOptions contains addition information for the Pick operation.
+type PickOptions struct {
+ // FullMethodName is the method name that NewClientStream() is called
+ // with. The canonical format is /service/Method.
+ FullMethodName string
+}
+
+// DoneInfo contains additional information for done.
+type DoneInfo struct {
+ // Err is the rpc error the RPC finished with. It could be nil.
+ Err error
+ // Trailer contains the metadata from the RPC's trailer, if present.
+ Trailer metadata.MD
+ // BytesSent indicates if any bytes have been sent to the server.
+ BytesSent bool
+ // BytesReceived indicates if any byte has been received from the server.
+ BytesReceived bool
+ // ServerLoad is the load received from server. It's usually sent as part of
+ // trailing metadata.
+ //
+ // The only supported type now is *orca_v1.LoadReport.
+ ServerLoad interface{}
+}
+
+var (
+ // ErrNoSubConnAvailable indicates no SubConn is available for pick().
+ // gRPC will block the RPC until a new picker is available via UpdateBalancerState().
+ ErrNoSubConnAvailable = errors.New("no SubConn is available")
+ // ErrTransientFailure indicates all SubConns are in TransientFailure.
+ // WaitForReady RPCs will block, non-WaitForReady RPCs will fail.
+ ErrTransientFailure = errors.New("all SubConns are in TransientFailure")
+)
+
+// 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().
+type Picker interface {
+ // Pick returns the SubConn to be used to send the RPC.
+ // The returned SubConn must be one returned by NewSubConn().
+ //
+ // 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).
+ //
+ // 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 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.
+ //
+ // 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)
+}
+
+// Balancer takes input from gRPC, manages SubConns, and collects and aggregates
+// the connectivity states.
+//
+// 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.
+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)
+ // Close closes the balancer. The balancer is not required to call
+ // ClientConn.RemoveSubConn for its existing SubConns.
+ Close()
+}
+
+// SubConnState describes the state of a SubConn.
+type SubConnState struct {
+ ConnectivityState connectivity.State
+ // TODO: add last connection error
+}
+
+// ClientConnState describes the state of a ClientConn relevant to the
+// balancer.
+type ClientConnState struct {
+ ResolverState resolver.State
+ // The parsed load balancing configuration returned by the builder's
+ // ParseConfig method, if implemented.
+ 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()
+}
+
+// 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.
+}
+
+// RecordTransition records state change happening in subConn and based on that
+// it evaluates what aggregated state should be.
+//
+// - If at least one SubConn in Ready, the aggregated state is Ready;
+// - Else if at least one SubConn in Connecting, the aggregated state is Connecting;
+// - Else the aggregated state is TransientFailure.
+//
+// Idle and Shutdown are not considered.
+func (cse *ConnectivityStateEvaluator) RecordTransition(oldState, newState connectivity.State) connectivity.State {
+ // Update counters.
+ for idx, state := range []connectivity.State{oldState, newState} {
+ updateVal := 2*uint64(idx) - 1 // -1 for oldState and +1 for new.
+ switch state {
+ case connectivity.Ready:
+ cse.numReady += updateVal
+ case connectivity.Connecting:
+ cse.numConnecting += updateVal
+ case connectivity.TransientFailure:
+ cse.numTransientFailure += updateVal
+ }
+ }
+
+ // Evaluate.
+ if cse.numReady > 0 {
+ return connectivity.Ready
+ }
+ if cse.numConnecting > 0 {
+ return connectivity.Connecting
+ }
+ return connectivity.TransientFailure
+}
diff --git a/vendor/google.golang.org/grpc/balancer/base/balancer.go b/vendor/google.golang.org/grpc/balancer/base/balancer.go
new file mode 100644
index 0000000..1af88f0
--- /dev/null
+++ b/vendor/google.golang.org/grpc/balancer/base/balancer.go
@@ -0,0 +1,184 @@
+/*
+ *
+ * Copyright 2017 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 base
+
+import (
+ "context"
+
+ "google.golang.org/grpc/balancer"
+ "google.golang.org/grpc/connectivity"
+ "google.golang.org/grpc/grpclog"
+ "google.golang.org/grpc/resolver"
+)
+
+type baseBuilder struct {
+ name string
+ pickerBuilder PickerBuilder
+ config Config
+}
+
+func (bb *baseBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
+ return &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,
+ }
+}
+
+func (bb *baseBuilder) Name() string {
+ return bb.name
+}
+
+type baseBalancer struct {
+ cc balancer.ClientConn
+ pickerBuilder PickerBuilder
+
+ csEvltr *balancer.ConnectivityStateEvaluator
+ state connectivity.State
+
+ subConns map[resolver.Address]balancer.SubConn
+ scStates map[balancer.SubConn]connectivity.State
+ picker balancer.Picker
+ config Config
+}
+
+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)
+ }
+ // 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 {
+ addrsSet[a] = struct{}{}
+ if _, ok := b.subConns[a]; !ok {
+ // 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)
+ continue
+ }
+ b.subConns[a] = sc
+ b.scStates[sc] = connectivity.Idle
+ sc.Connect()
+ }
+ }
+ for a, sc := range b.subConns {
+ // a was removed by resolver.
+ if _, ok := addrsSet[a]; !ok {
+ 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.
+ }
+ }
+}
+
+// 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,
+// - built by the pickerBuilder with all READY SubConns otherwise.
+func (b *baseBalancer) regeneratePicker() {
+ if b.state == connectivity.TransientFailure {
+ b.picker = NewErrPicker(balancer.ErrTransientFailure)
+ return
+ }
+ readySCs := make(map[resolver.Address]balancer.SubConn)
+
+ // 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
+ }
+ }
+ b.picker = b.pickerBuilder.Build(readySCs)
+}
+
+func (b *baseBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
+ panic("not implemented")
+}
+
+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)
+ }
+ 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)
+ }
+ return
+ }
+ b.scStates[sc] = s
+ switch s {
+ case connectivity.Idle:
+ sc.Connect()
+ case connectivity.Shutdown:
+ // 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)
+ }
+
+ 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
+ if (s == connectivity.Ready) != (oldS == connectivity.Ready) ||
+ (b.state == connectivity.TransientFailure) != (oldAggrState == connectivity.TransientFailure) {
+ b.regeneratePicker()
+ }
+
+ b.cc.UpdateBalancerState(b.state, b.picker)
+}
+
+// Close is a nop because base balancer doesn't have internal state to clean up,
+// and it doesn't need to call RemoveSubConn for the SubConns.
+func (b *baseBalancer) Close() {
+}
+
+// NewErrPicker returns a picker that always returns err on Pick().
+func NewErrPicker(err error) balancer.Picker {
+ return &errPicker{err: err}
+}
+
+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
+}
diff --git a/vendor/google.golang.org/grpc/balancer/base/base.go b/vendor/google.golang.org/grpc/balancer/base/base.go
new file mode 100644
index 0000000..34b1f29
--- /dev/null
+++ b/vendor/google.golang.org/grpc/balancer/base/base.go
@@ -0,0 +1,64 @@
+/*
+ *
+ * Copyright 2017 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 base defines a balancer base that can be used to build balancers with
+// different picking algorithms.
+//
+// The base balancer creates a new SubConn for each resolved address. The
+// provided picker will only be notified about READY SubConns.
+//
+// This package is the base of round_robin balancer, its purpose is to be used
+// to build round_robin like balancers with complex picking algorithms.
+// Balancers with more complicated logic should try to implement a balancer
+// builder from scratch.
+//
+// All APIs in this package are experimental.
+package base
+
+import (
+ "google.golang.org/grpc/balancer"
+ "google.golang.org/grpc/resolver"
+)
+
+// 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
+}
+
+// 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{})
+}
+
+// Config contains the config info about the base balancer builder.
+type Config struct {
+ // HealthCheck indicates whether health checking should be enabled for this specific balancer.
+ HealthCheck bool
+}
+
+// NewBalancerBuilderWithConfig returns a base balancer builder configured by the provided config.
+func NewBalancerBuilderWithConfig(name string, pb PickerBuilder, config Config) balancer.Builder {
+ return &baseBuilder{
+ name: name,
+ pickerBuilder: pb,
+ config: config,
+ }
+}
diff --git a/vendor/google.golang.org/grpc/balancer/roundrobin/roundrobin.go b/vendor/google.golang.org/grpc/balancer/roundrobin/roundrobin.go
new file mode 100644
index 0000000..29f7a4d
--- /dev/null
+++ b/vendor/google.golang.org/grpc/balancer/roundrobin/roundrobin.go
@@ -0,0 +1,83 @@
+/*
+ *
+ * Copyright 2017 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 roundrobin defines a roundrobin balancer. Roundrobin balancer is
+// installed as one of the default balancers in gRPC, users don't need to
+// explicitly install this balancer.
+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"
+
+// newBuilder creates a new roundrobin balancer builder.
+func newBuilder() balancer.Builder {
+ return base.NewBalancerBuilderWithConfig(Name, &rrPickerBuilder{}, base.Config{HealthCheck: true})
+}
+
+func init() {
+ balancer.Register(newBuilder())
+}
+
+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 {
+ return base.NewErrPicker(balancer.ErrNoSubConnAvailable)
+ }
+ var scs []balancer.SubConn
+ for _, sc := range readySCs {
+ scs = append(scs, sc)
+ }
+ return &rrPicker{
+ subConns: scs,
+ // Start at a random index, as the same RR balancer rebuilds a new
+ // picker when SubConn states change, and we don't want to apply excess
+ // load to the first server in the list.
+ next: grpcrand.Intn(len(scs)),
+ }
+}
+
+type rrPicker struct {
+ // subConns is the snapshot of the roundrobin balancer when this picker was
+ // created. The slice is immutable. Each Get() will do a round robin
+ // selection from it and return the selected SubConn.
+ subConns []balancer.SubConn
+
+ mu sync.Mutex
+ next int
+}
+
+func (p *rrPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+ p.mu.Lock()
+ sc := p.subConns[p.next]
+ p.next = (p.next + 1) % len(p.subConns)
+ p.mu.Unlock()
+ return sc, nil, nil
+}