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1 | /* |
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 | ||
19 | package base | |
20 | ||
21 | import ( | |
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 | ||
30 | type baseBuilder struct { | |
31 | name string | |
32 | pickerBuilder PickerBuilder | |
33 | config Config | |
34 | } | |
35 | ||
36 | func (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), | |
43 | csEvltr: &balancer.ConnectivityStateEvaluator{}, | |
44 | // 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 | ||
52 | func (bb *baseBuilder) Name() string { | |
53 | return bb.name | |
54 | } | |
55 | ||
56 | type baseBalancer struct { | |
57 | cc balancer.ClientConn | |
58 | pickerBuilder PickerBuilder | |
59 | ||
60 | csEvltr *balancer.ConnectivityStateEvaluator | |
61 | 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 | ||
69 | func (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. | |
106 | func (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 | ||
122 | func (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 | |
140 | b.state = b.csEvltr.RecordTransition(oldS, s) | |
141 | ||
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. | |
157 | func (b *baseBalancer) Close() { | |
158 | } | |
159 | ||
160 | // NewErrPicker returns a picker that always returns err on Pick(). | |
161 | func NewErrPicker(err error) balancer.Picker { | |
162 | return &errPicker{err: err} | |
163 | } | |
164 | ||
165 | type errPicker struct { | |
166 | err error // Pick() always returns this err. | |
167 | } | |
168 | ||
169 | func (p *errPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) { | |
170 | return nil, nil, p.err | |
171 | } |