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khenaidooac637102019-01-14 15:44:34 -05001/*
2 *
3 * Copyright 2017 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19package base
20
21import (
22 "context"
23
24 "google.golang.org/grpc/balancer"
25 "google.golang.org/grpc/connectivity"
26 "google.golang.org/grpc/grpclog"
27 "google.golang.org/grpc/resolver"
28)
29
30type baseBuilder struct {
31 name string
32 pickerBuilder PickerBuilder
33 config Config
34}
35
36func (bb *baseBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
37 return &baseBalancer{
38 cc: cc,
39 pickerBuilder: bb.pickerBuilder,
40
41 subConns: make(map[resolver.Address]balancer.SubConn),
42 scStates: make(map[balancer.SubConn]connectivity.State),
Stephane Barbarie260a5632019-02-26 16:12:49 -050043 csEvltr: &balancer.ConnectivityStateEvaluator{},
khenaidooac637102019-01-14 15:44:34 -050044 // Initialize picker to a picker that always return
45 // ErrNoSubConnAvailable, because when state of a SubConn changes, we
46 // may call UpdateBalancerState with this picker.
47 picker: NewErrPicker(balancer.ErrNoSubConnAvailable),
48 config: bb.config,
49 }
50}
51
52func (bb *baseBuilder) Name() string {
53 return bb.name
54}
55
56type baseBalancer struct {
57 cc balancer.ClientConn
58 pickerBuilder PickerBuilder
59
Stephane Barbarie260a5632019-02-26 16:12:49 -050060 csEvltr *balancer.ConnectivityStateEvaluator
khenaidooac637102019-01-14 15:44:34 -050061 state connectivity.State
62
63 subConns map[resolver.Address]balancer.SubConn
64 scStates map[balancer.SubConn]connectivity.State
65 picker balancer.Picker
66 config Config
67}
68
69func (b *baseBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
70 if err != nil {
71 grpclog.Infof("base.baseBalancer: HandleResolvedAddrs called with error %v", err)
72 return
73 }
74 grpclog.Infoln("base.baseBalancer: got new resolved addresses: ", addrs)
75 // addrsSet is the set converted from addrs, it's used for quick lookup of an address.
76 addrsSet := make(map[resolver.Address]struct{})
77 for _, a := range addrs {
78 addrsSet[a] = struct{}{}
79 if _, ok := b.subConns[a]; !ok {
80 // a is a new address (not existing in b.subConns).
81 sc, err := b.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{HealthCheckEnabled: b.config.HealthCheck})
82 if err != nil {
83 grpclog.Warningf("base.baseBalancer: failed to create new SubConn: %v", err)
84 continue
85 }
86 b.subConns[a] = sc
87 b.scStates[sc] = connectivity.Idle
88 sc.Connect()
89 }
90 }
91 for a, sc := range b.subConns {
92 // a was removed by resolver.
93 if _, ok := addrsSet[a]; !ok {
94 b.cc.RemoveSubConn(sc)
95 delete(b.subConns, a)
96 // Keep the state of this sc in b.scStates until sc's state becomes Shutdown.
97 // The entry will be deleted in HandleSubConnStateChange.
98 }
99 }
100}
101
102// regeneratePicker takes a snapshot of the balancer, and generates a picker
103// from it. The picker is
104// - errPicker with ErrTransientFailure if the balancer is in TransientFailure,
105// - built by the pickerBuilder with all READY SubConns otherwise.
106func (b *baseBalancer) regeneratePicker() {
107 if b.state == connectivity.TransientFailure {
108 b.picker = NewErrPicker(balancer.ErrTransientFailure)
109 return
110 }
111 readySCs := make(map[resolver.Address]balancer.SubConn)
112
113 // Filter out all ready SCs from full subConn map.
114 for addr, sc := range b.subConns {
115 if st, ok := b.scStates[sc]; ok && st == connectivity.Ready {
116 readySCs[addr] = sc
117 }
118 }
119 b.picker = b.pickerBuilder.Build(readySCs)
120}
121
122func (b *baseBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
123 grpclog.Infof("base.baseBalancer: handle SubConn state change: %p, %v", sc, s)
124 oldS, ok := b.scStates[sc]
125 if !ok {
126 grpclog.Infof("base.baseBalancer: got state changes for an unknown SubConn: %p, %v", sc, s)
127 return
128 }
129 b.scStates[sc] = s
130 switch s {
131 case connectivity.Idle:
132 sc.Connect()
133 case connectivity.Shutdown:
134 // When an address was removed by resolver, b called RemoveSubConn but
135 // kept the sc's state in scStates. Remove state for this sc here.
136 delete(b.scStates, sc)
137 }
138
139 oldAggrState := b.state
Stephane Barbarie260a5632019-02-26 16:12:49 -0500140 b.state = b.csEvltr.RecordTransition(oldS, s)
khenaidooac637102019-01-14 15:44:34 -0500141
142 // Regenerate picker when one of the following happens:
143 // - this sc became ready from not-ready
144 // - this sc became not-ready from ready
145 // - the aggregated state of balancer became TransientFailure from non-TransientFailure
146 // - the aggregated state of balancer became non-TransientFailure from TransientFailure
147 if (s == connectivity.Ready) != (oldS == connectivity.Ready) ||
148 (b.state == connectivity.TransientFailure) != (oldAggrState == connectivity.TransientFailure) {
149 b.regeneratePicker()
150 }
151
152 b.cc.UpdateBalancerState(b.state, b.picker)
153}
154
155// Close is a nop because base balancer doesn't have internal state to clean up,
156// and it doesn't need to call RemoveSubConn for the SubConns.
157func (b *baseBalancer) Close() {
158}
159
160// NewErrPicker returns a picker that always returns err on Pick().
161func NewErrPicker(err error) balancer.Picker {
162 return &errPicker{err: err}
163}
164
165type errPicker struct {
166 err error // Pick() always returns this err.
167}
168
169func (p *errPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
170 return nil, nil, p.err
171}