271 lines
9.0 KiB
Go
271 lines
9.0 KiB
Go
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/*
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*
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* Copyright 2017 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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package base
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import (
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"errors"
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"fmt"
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"google.golang.org/grpc/attributes"
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"google.golang.org/grpc/balancer"
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"google.golang.org/grpc/connectivity"
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"google.golang.org/grpc/grpclog"
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"google.golang.org/grpc/resolver"
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)
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var logger = grpclog.Component("balancer")
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type baseBuilder struct {
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name string
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pickerBuilder PickerBuilder
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config Config
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}
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func (bb *baseBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
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bal := &baseBalancer{
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cc: cc,
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pickerBuilder: bb.pickerBuilder,
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subConns: make(map[resolver.Address]subConnInfo),
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scStates: make(map[balancer.SubConn]connectivity.State),
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csEvltr: &balancer.ConnectivityStateEvaluator{},
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config: bb.config,
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}
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// Initialize picker to a picker that always returns
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// ErrNoSubConnAvailable, because when state of a SubConn changes, we
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// may call UpdateState with this picker.
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bal.picker = NewErrPicker(balancer.ErrNoSubConnAvailable)
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return bal
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}
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func (bb *baseBuilder) Name() string {
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return bb.name
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}
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type subConnInfo struct {
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subConn balancer.SubConn
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attrs *attributes.Attributes
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}
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type baseBalancer struct {
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cc balancer.ClientConn
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pickerBuilder PickerBuilder
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csEvltr *balancer.ConnectivityStateEvaluator
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state connectivity.State
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subConns map[resolver.Address]subConnInfo // `attributes` is stripped from the keys of this map (the addresses)
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scStates map[balancer.SubConn]connectivity.State
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picker balancer.Picker
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config Config
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resolverErr error // the last error reported by the resolver; cleared on successful resolution
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connErr error // the last connection error; cleared upon leaving TransientFailure
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}
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func (b *baseBalancer) ResolverError(err error) {
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b.resolverErr = err
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if len(b.subConns) == 0 {
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b.state = connectivity.TransientFailure
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}
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if b.state != connectivity.TransientFailure {
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// The picker will not change since the balancer does not currently
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// report an error.
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return
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}
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b.regeneratePicker()
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b.cc.UpdateState(balancer.State{
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ConnectivityState: b.state,
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Picker: b.picker,
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})
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}
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func (b *baseBalancer) UpdateClientConnState(s balancer.ClientConnState) error {
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// TODO: handle s.ResolverState.ServiceConfig?
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if logger.V(2) {
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logger.Info("base.baseBalancer: got new ClientConn state: ", s)
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}
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// Successful resolution; clear resolver error and ensure we return nil.
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b.resolverErr = nil
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// addrsSet is the set converted from addrs, it's used for quick lookup of an address.
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addrsSet := make(map[resolver.Address]struct{})
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for _, a := range s.ResolverState.Addresses {
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// Strip attributes from addresses before using them as map keys. So
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// that when two addresses only differ in attributes pointers (but with
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// the same attribute content), they are considered the same address.
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//
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// Note that this doesn't handle the case where the attribute content is
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// different. So if users want to set different attributes to create
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// duplicate connections to the same backend, it doesn't work. This is
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// fine for now, because duplicate is done by setting Metadata today.
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//
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// TODO: read attributes to handle duplicate connections.
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aNoAttrs := a
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aNoAttrs.Attributes = nil
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addrsSet[aNoAttrs] = struct{}{}
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if scInfo, ok := b.subConns[aNoAttrs]; !ok {
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// a is a new address (not existing in b.subConns).
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//
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// When creating SubConn, the original address with attributes is
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// passed through. So that connection configurations in attributes
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// (like creds) will be used.
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sc, err := b.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{HealthCheckEnabled: b.config.HealthCheck})
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if err != nil {
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logger.Warningf("base.baseBalancer: failed to create new SubConn: %v", err)
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continue
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}
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b.subConns[aNoAttrs] = subConnInfo{subConn: sc, attrs: a.Attributes}
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b.scStates[sc] = connectivity.Idle
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sc.Connect()
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} else {
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// Always update the subconn's address in case the attributes
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// changed.
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//
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// The SubConn does a reflect.DeepEqual of the new and old
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// addresses. So this is a noop if the current address is the same
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// as the old one (including attributes).
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scInfo.attrs = a.Attributes
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b.subConns[aNoAttrs] = scInfo
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b.cc.UpdateAddresses(scInfo.subConn, []resolver.Address{a})
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}
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}
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for a, scInfo := range b.subConns {
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// a was removed by resolver.
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if _, ok := addrsSet[a]; !ok {
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b.cc.RemoveSubConn(scInfo.subConn)
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delete(b.subConns, a)
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// Keep the state of this sc in b.scStates until sc's state becomes Shutdown.
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// The entry will be deleted in UpdateSubConnState.
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}
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}
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// If resolver state contains no addresses, return an error so ClientConn
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// will trigger re-resolve. Also records this as an resolver error, so when
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// the overall state turns transient failure, the error message will have
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// the zero address information.
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if len(s.ResolverState.Addresses) == 0 {
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b.ResolverError(errors.New("produced zero addresses"))
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return balancer.ErrBadResolverState
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}
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return nil
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}
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// mergeErrors builds an error from the last connection error and the last
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// resolver error. Must only be called if b.state is TransientFailure.
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func (b *baseBalancer) mergeErrors() error {
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// connErr must always be non-nil unless there are no SubConns, in which
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// case resolverErr must be non-nil.
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if b.connErr == nil {
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return fmt.Errorf("last resolver error: %v", b.resolverErr)
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}
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if b.resolverErr == nil {
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return fmt.Errorf("last connection error: %v", b.connErr)
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}
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return fmt.Errorf("last connection error: %v; last resolver error: %v", b.connErr, b.resolverErr)
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}
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// regeneratePicker takes a snapshot of the balancer, and generates a picker
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// from it. The picker is
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// - errPicker if the balancer is in TransientFailure,
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// - built by the pickerBuilder with all READY SubConns otherwise.
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func (b *baseBalancer) regeneratePicker() {
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if b.state == connectivity.TransientFailure {
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b.picker = NewErrPicker(b.mergeErrors())
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return
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}
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readySCs := make(map[balancer.SubConn]SubConnInfo)
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// Filter out all ready SCs from full subConn map.
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for addr, scInfo := range b.subConns {
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if st, ok := b.scStates[scInfo.subConn]; ok && st == connectivity.Ready {
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addr.Attributes = scInfo.attrs
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readySCs[scInfo.subConn] = SubConnInfo{Address: addr}
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}
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}
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b.picker = b.pickerBuilder.Build(PickerBuildInfo{ReadySCs: readySCs})
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}
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func (b *baseBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
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s := state.ConnectivityState
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if logger.V(2) {
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logger.Infof("base.baseBalancer: handle SubConn state change: %p, %v", sc, s)
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}
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oldS, ok := b.scStates[sc]
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if !ok {
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if logger.V(2) {
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logger.Infof("base.baseBalancer: got state changes for an unknown SubConn: %p, %v", sc, s)
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}
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return
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}
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if oldS == connectivity.TransientFailure && s == connectivity.Connecting {
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// Once a subconn enters TRANSIENT_FAILURE, ignore subsequent
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// CONNECTING transitions to prevent the aggregated state from being
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// always CONNECTING when many backends exist but are all down.
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return
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}
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b.scStates[sc] = s
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switch s {
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case connectivity.Idle:
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sc.Connect()
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case connectivity.Shutdown:
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// When an address was removed by resolver, b called RemoveSubConn but
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// kept the sc's state in scStates. Remove state for this sc here.
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delete(b.scStates, sc)
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case connectivity.TransientFailure:
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// Save error to be reported via picker.
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b.connErr = state.ConnectionError
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}
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b.state = b.csEvltr.RecordTransition(oldS, s)
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// Regenerate picker when one of the following happens:
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// - this sc entered or left ready
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// - the aggregated state of balancer is TransientFailure
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// (may need to update error message)
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if (s == connectivity.Ready) != (oldS == connectivity.Ready) ||
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b.state == connectivity.TransientFailure {
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b.regeneratePicker()
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}
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b.cc.UpdateState(balancer.State{ConnectivityState: b.state, Picker: b.picker})
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}
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// Close is a nop because base balancer doesn't have internal state to clean up,
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// and it doesn't need to call RemoveSubConn for the SubConns.
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func (b *baseBalancer) Close() {
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}
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// NewErrPicker returns a Picker that always returns err on Pick().
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func NewErrPicker(err error) balancer.Picker {
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return &errPicker{err: err}
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}
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// NewErrPickerV2 is temporarily defined for backward compatibility reasons.
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//
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// Deprecated: use NewErrPicker instead.
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var NewErrPickerV2 = NewErrPicker
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type errPicker struct {
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err error // Pick() always returns this err.
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}
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func (p *errPicker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
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return balancer.PickResult{}, p.err
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}
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