agent.go
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
package main
import (
"log"
"os"
"sync"
"time"
"github.com/hashicorp/memberlist"
"github.com/hashicorp/serf/serf"
)
// Agent starts and manages a Serf & adds
// service discovery
type Agent struct {
conf *Config
serfConf *serf.Config
eventCh chan serf.Event
// i doubt we care about handling events,
// but i'm leaving this here just in case
// eventHandlerList []EventHandler
// eventHandlersLock sync.Mutex
// This is the underlying Serf we are wrapping
serf *serf.Serf
// this channel receiving a signal = shutdown
shutdown bool
shutdownCh chan struct{}
shutdownLock sync.Mutex
}
func Create(conf *Config, serfConf *serf.Config) (*Agent) {
// Create a channel to listen for events from Serf
eventCh := make(chan serf.Event, 64)
serfConf.EventCh = eventCh
// Setup the agent
agent := &Agent{
conf: conf,
serfConf: serfConf,
eventCh: eventCh,
shutdownCh: make(chan struct{}),
}
return agent
}
// setupAgent calls Create
func SetupAgent(config *Config) *Agent {
bindIP, bindPort, err := config.AddrParts(config.BindAddr)
if err != nil {
log.Panic(err)
}
serfConfig := serf.DefaultConfig()
if os.Getenv("CASCADE_BIND") != "" {
config.BindAddr = os.Getenv("CASCADE_BIND")
}
serfConfig.MemberlistConfig.BindAddr = bindIP
serfConfig.MemberlistConfig.BindPort = bindPort
serfConfig.MemberlistConfig.AdvertiseAddr = ""
serfConfig.MemberlistConfig.AdvertisePort = 0
serfConfig.ProtocolVersion = uint8(serf.ProtocolVersionMax)
serfConfig.CoalescePeriod = 3 * time.Second
serfConfig.QuiescentPeriod = time.Second
serfConfig.QueryResponseSizeLimit = 1024
serfConfig.QuerySizeLimit = 1024
serfConfig.UserEventSizeLimit = 512
serfConfig.UserCoalescePeriod = 3 * time.Second
serfConfig.UserQuiescentPeriod = time.Second
// TODO: look at reconnect/tombstone settings w more scrutiny
serfConfig.ReconnectInterval = 0
serfConfig.ReconnectTimeout = 0
serfConfig.TombstoneTimeout = 0
serfConfig.BroadcastTimeout = 0
// TODO: what are the implications of true here o_O
serfConfig.EnableNameConflictResolution = true
// hardcode DefaultWANConfig because cascade is designed to be
// used as a single global system.
serfConfig.MemberlistConfig = memberlist.DefaultWANConfig()
serfConfig.MemberlistConfig.BindAddr = bindIP
serfConfig.MemberlistConfig.BindPort = bindPort
agent := Create(config, serfConfig)
return agent
}
func (a *Agent) eventLoop() {
serfShutdownCh := a.serf.ShutdownCh()
for {
select {
case e := <-a.eventCh:
log.Printf("[INFO] agent: Received event: %s", e.String())
case <-serfShutdownCh:
log.Printf("[WARN] agent: Serf shutdown detected, quitting")
a.Shutdown()
return
case <-a.shutdownCh:
return
}
}
}
// Shutdown closes this agent and all of its processes. Should be preceded
// by a Leave for a graceful shutdown.
func (a *Agent) Shutdown() error {
a.shutdownLock.Lock()
defer a.shutdownLock.Unlock()
if a.shutdown {
return nil
}
if a.serf == nil {
goto EXIT
}
log.Println("[INFO] agent: requesting serf shutdown")
if err := a.serf.Shutdown(); err != nil {
return err
}
EXIT:
log.Println("[INFO] agent: shutdown complete")
a.shutdown = true
close(a.shutdownCh)
return nil
}