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
package notify
import (
"context"
"net"
"os"
"strconv"
"strings"
"time"
)
const (
EnvSocket = "NOTIFY_SOCKET"
EnvWatchdogUSec = "WATCHDOG_USEC"
)
func Ready() error { return send("READY=1") }
func Watchdog() error { return send("WATCHDOG=1") }
func send(state string) error {
addr := os.Getenv(EnvSocket)
if addr == "" {
return nil
}
c, err := net.Dial("unixgram", socketName(addr))
if err != nil {
return err
}
defer c.Close()
_, err = c.Write([]byte(state))
return err
}
func socketName(addr string) string {
if strings.HasPrefix(addr, "@") {
return "\x00" + addr[1:]
}
return addr
}
func WatchdogInterval() time.Duration {
usec, err := strconv.ParseInt(strings.TrimSpace(os.Getenv(EnvWatchdogUSec)), 10, 64)
if err != nil || usec <= 0 {
return 0
}
return time.Duration(usec) * time.Microsecond
}
func KeepAlive(ctx context.Context, onError func(error)) {
interval := WatchdogInterval()
if interval <= 0 || os.Getenv(EnvSocket) == "" {
return
}
tick := time.NewTicker(interval / 2)
defer tick.Stop()
for {
select {
case <-ctx.Done():
return
case <-tick.C:
if err := Watchdog(); err != nil && onError != nil {
onError(err)
}
}
}
}
