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Scott Baker2d897982019-09-24 11:50:08 -07001/*
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 grpc
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
30// PickFirstBalancerName is the name of the pick_first balancer.
31const PickFirstBalancerName = "pick_first"
32
33func newPickfirstBuilder() balancer.Builder {
34 return &pickfirstBuilder{}
35}
36
37type pickfirstBuilder struct{}
38
39func (*pickfirstBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
40 return &pickfirstBalancer{cc: cc}
41}
42
43func (*pickfirstBuilder) Name() string {
44 return PickFirstBalancerName
45}
46
47type pickfirstBalancer struct {
48 cc balancer.ClientConn
49 sc balancer.SubConn
50}
51
52func (b *pickfirstBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
53 if err != nil {
54 grpclog.Infof("pickfirstBalancer: HandleResolvedAddrs called with error %v", err)
55 return
56 }
57 if b.sc == nil {
58 b.sc, err = b.cc.NewSubConn(addrs, balancer.NewSubConnOptions{})
59 if err != nil {
60 //TODO(yuxuanli): why not change the cc state to Idle?
61 grpclog.Errorf("pickfirstBalancer: failed to NewSubConn: %v", err)
62 return
63 }
64 b.cc.UpdateBalancerState(connectivity.Idle, &picker{sc: b.sc})
65 b.sc.Connect()
66 } else {
67 b.sc.UpdateAddresses(addrs)
68 b.sc.Connect()
69 }
70}
71
72func (b *pickfirstBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
73 grpclog.Infof("pickfirstBalancer: HandleSubConnStateChange: %p, %v", sc, s)
74 if b.sc != sc {
75 grpclog.Infof("pickfirstBalancer: ignored state change because sc is not recognized")
76 return
77 }
78 if s == connectivity.Shutdown {
79 b.sc = nil
80 return
81 }
82
83 switch s {
84 case connectivity.Ready, connectivity.Idle:
85 b.cc.UpdateBalancerState(s, &picker{sc: sc})
86 case connectivity.Connecting:
87 b.cc.UpdateBalancerState(s, &picker{err: balancer.ErrNoSubConnAvailable})
88 case connectivity.TransientFailure:
89 b.cc.UpdateBalancerState(s, &picker{err: balancer.ErrTransientFailure})
90 }
91}
92
93func (b *pickfirstBalancer) Close() {
94}
95
96type picker struct {
97 err error
98 sc balancer.SubConn
99}
100
101func (p *picker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
102 if p.err != nil {
103 return nil, nil, p.err
104 }
105 return p.sc, nil, nil
106}
107
108func init() {
109 balancer.Register(newPickfirstBuilder())
110}