1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
|
// Copyright 2016 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package command
import (
"context"
"errors"
"os"
"os/signal"
"syscall"
"go.etcd.io/etcd/client/v3"
"go.etcd.io/etcd/client/v3/concurrency"
"go.etcd.io/etcd/pkg/v3/cobrautl"
"github.com/spf13/cobra"
)
var (
electListen bool
)
// NewElectCommand returns the cobra command for "elect".
func NewElectCommand() *cobra.Command {
cmd := &cobra.Command{
Use: "elect <election-name> [proposal]",
Short: "Observes and participates in leader election",
Run: electCommandFunc,
}
cmd.Flags().BoolVarP(&electListen, "listen", "l", false, "observation mode")
return cmd
}
func electCommandFunc(cmd *cobra.Command, args []string) {
if len(args) != 1 && len(args) != 2 {
cobrautl.ExitWithError(cobrautl.ExitBadArgs, errors.New("elect takes one election name argument and an optional proposal argument"))
}
c := mustClientFromCmd(cmd)
var err error
if len(args) == 1 {
if !electListen {
cobrautl.ExitWithError(cobrautl.ExitBadArgs, errors.New("no proposal argument but -l not set"))
}
err = observe(c, args[0])
} else {
if electListen {
cobrautl.ExitWithError(cobrautl.ExitBadArgs, errors.New("proposal given but -l is set"))
}
err = campaign(c, args[0], args[1])
}
if err != nil {
cobrautl.ExitWithError(cobrautl.ExitError, err)
}
}
func observe(c *clientv3.Client, election string) error {
s, err := concurrency.NewSession(c)
if err != nil {
return err
}
e := concurrency.NewElection(s, election)
ctx, cancel := context.WithCancel(context.TODO())
donec := make(chan struct{})
sigc := make(chan os.Signal, 1)
signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)
go func() {
<-sigc
cancel()
}()
go func() {
for resp := range e.Observe(ctx) {
display.Get(resp)
}
close(donec)
}()
<-donec
select {
case <-ctx.Done():
default:
return errors.New("elect: observer lost")
}
return nil
}
func campaign(c *clientv3.Client, election string, prop string) error {
s, err := concurrency.NewSession(c)
if err != nil {
return err
}
e := concurrency.NewElection(s, election)
ctx, cancel := context.WithCancel(context.TODO())
donec := make(chan struct{})
sigc := make(chan os.Signal, 1)
signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)
go func() {
<-sigc
cancel()
close(donec)
}()
if err = e.Campaign(ctx, prop); err != nil {
return err
}
// print key since elected
resp, err := c.Get(ctx, e.Key())
if err != nil {
return err
}
display.Get(*resp)
select {
case <-donec:
case <-s.Done():
return errors.New("elect: session expired")
}
return e.Resign(context.TODO())
}
|
