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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 grpc | |
20 | ||
21 | import ( | |
22 | "context" | |
23 | "io" | |
24 | "sync" | |
25 | ||
26 | "google.golang.org/grpc/balancer" | |
27 | "google.golang.org/grpc/codes" | |
28 | "google.golang.org/grpc/grpclog" | |
29 | "google.golang.org/grpc/internal/channelz" | |
30 | "google.golang.org/grpc/internal/transport" | |
31 | "google.golang.org/grpc/status" | |
32 | ) | |
33 | ||
34 | // pickerWrapper is a wrapper of balancer.Picker. It blocks on certain pick | |
35 | // actions and unblock when there's a picker update. | |
36 | type pickerWrapper struct { | |
37 | mu sync.Mutex | |
38 | done bool | |
39 | blockingCh chan struct{} | |
40 | picker balancer.Picker | |
41 | ||
42 | // The latest connection happened. | |
43 | connErrMu sync.Mutex | |
44 | connErr error | |
45 | } | |
46 | ||
47 | func newPickerWrapper() *pickerWrapper { | |
48 | bp := &pickerWrapper{blockingCh: make(chan struct{})} | |
49 | return bp | |
50 | } | |
51 | ||
52 | func (bp *pickerWrapper) updateConnectionError(err error) { | |
53 | bp.connErrMu.Lock() | |
54 | bp.connErr = err | |
55 | bp.connErrMu.Unlock() | |
56 | } | |
57 | ||
58 | func (bp *pickerWrapper) connectionError() error { | |
59 | bp.connErrMu.Lock() | |
60 | err := bp.connErr | |
61 | bp.connErrMu.Unlock() | |
62 | return err | |
63 | } | |
64 | ||
65 | // updatePicker is called by UpdateBalancerState. It unblocks all blocked pick. | |
66 | func (bp *pickerWrapper) updatePicker(p balancer.Picker) { | |
67 | bp.mu.Lock() | |
68 | if bp.done { | |
69 | bp.mu.Unlock() | |
70 | return | |
71 | } | |
72 | bp.picker = p | |
73 | // bp.blockingCh should never be nil. | |
74 | close(bp.blockingCh) | |
75 | bp.blockingCh = make(chan struct{}) | |
76 | bp.mu.Unlock() | |
77 | } | |
78 | ||
79 | func doneChannelzWrapper(acw *acBalancerWrapper, done func(balancer.DoneInfo)) func(balancer.DoneInfo) { | |
80 | acw.mu.Lock() | |
81 | ac := acw.ac | |
82 | acw.mu.Unlock() | |
83 | ac.incrCallsStarted() | |
84 | return func(b balancer.DoneInfo) { | |
85 | if b.Err != nil && b.Err != io.EOF { | |
86 | ac.incrCallsFailed() | |
87 | } else { | |
88 | ac.incrCallsSucceeded() | |
89 | } | |
90 | if done != nil { | |
91 | done(b) | |
92 | } | |
93 | } | |
94 | } | |
95 | ||
96 | // pick returns the transport that will be used for the RPC. | |
97 | // It may block in the following cases: | |
98 | // - there's no picker | |
99 | // - the current picker returns ErrNoSubConnAvailable | |
100 | // - the current picker returns other errors and failfast is false. | |
101 | // - the subConn returned by the current picker is not READY | |
102 | // When one of these situations happens, pick blocks until the picker gets updated. | |
103 | func (bp *pickerWrapper) pick(ctx context.Context, failfast bool, opts balancer.PickOptions) (transport.ClientTransport, func(balancer.DoneInfo), error) { | |
104 | var ( | |
105 | p balancer.Picker | |
106 | ch chan struct{} | |
107 | ) | |
108 | ||
109 | for { | |
110 | bp.mu.Lock() | |
111 | if bp.done { | |
112 | bp.mu.Unlock() | |
113 | return nil, nil, ErrClientConnClosing | |
114 | } | |
115 | ||
116 | if bp.picker == nil { | |
117 | ch = bp.blockingCh | |
118 | } | |
119 | if ch == bp.blockingCh { | |
120 | // This could happen when either: | |
121 | // - bp.picker is nil (the previous if condition), or | |
122 | // - has called pick on the current picker. | |
123 | bp.mu.Unlock() | |
124 | select { | |
125 | case <-ctx.Done(): | |
126 | return nil, nil, ctx.Err() | |
127 | case <-ch: | |
128 | } | |
129 | continue | |
130 | } | |
131 | ||
132 | ch = bp.blockingCh | |
133 | p = bp.picker | |
134 | bp.mu.Unlock() | |
135 | ||
136 | subConn, done, err := p.Pick(ctx, opts) | |
137 | ||
138 | if err != nil { | |
139 | switch err { | |
140 | case balancer.ErrNoSubConnAvailable: | |
141 | continue | |
142 | case balancer.ErrTransientFailure: | |
143 | if !failfast { | |
144 | continue | |
145 | } | |
146 | return nil, nil, status.Errorf(codes.Unavailable, "%v, latest connection error: %v", err, bp.connectionError()) | |
147 | default: | |
148 | // err is some other error. | |
149 | return nil, nil, toRPCErr(err) | |
150 | } | |
151 | } | |
152 | ||
153 | acw, ok := subConn.(*acBalancerWrapper) | |
154 | if !ok { | |
155 | grpclog.Infof("subconn returned from pick is not *acBalancerWrapper") | |
156 | continue | |
157 | } | |
158 | if t, ok := acw.getAddrConn().getReadyTransport(); ok { | |
159 | if channelz.IsOn() { | |
160 | return t, doneChannelzWrapper(acw, done), nil | |
161 | } | |
162 | return t, done, nil | |
163 | } | |
164 | grpclog.Infof("blockingPicker: the picked transport is not ready, loop back to repick") | |
165 | // If ok == false, ac.state is not READY. | |
166 | // A valid picker always returns READY subConn. This means the state of ac | |
167 | // just changed, and picker will be updated shortly. | |
168 | // continue back to the beginning of the for loop to repick. | |
169 | } | |
170 | } | |
171 | ||
172 | func (bp *pickerWrapper) close() { | |
173 | bp.mu.Lock() | |
174 | defer bp.mu.Unlock() | |
175 | if bp.done { | |
176 | return | |
177 | } | |
178 | bp.done = true | |
179 | close(bp.blockingCh) | |
180 | } |