I want to spawn long-running child processes that survive when the main process restarts/dies. This works fine when running from the terminal:
$ cat exectest.go
package main
import (
"log"
"os"
"os/exec"
"syscall"
"time"
)
func main() {
if len(os.Args) == 2 && os.Args[1] == "child" {
for {
time.Sleep(time.Second)
}
} else {
cmd := exec.Command(os.Args[0], "child")
cmd.SysProcAttr = &syscall.SysProcAttr{Setsid: true}
log.Printf("child exited: %v", cmd.Run())
}
}
$ go build
$ ./exectest
^Z
[1]+ Stopped ./exectest
$ bg
[1]+ ./exectest &
$ ps -ef | grep exectest | grep -v grep | grep -v vim
snowm 7914 5650 0 23:44 pts/7 00:00:00 ./exectest
snowm 7916 7914 0 23:44 ? 00:00:00 ./exectest child
$ kill -INT 7914 # kill parent process
[1]+ Exit 2 ./exectest
$ ps -ef | grep exectest | grep -v grep | grep -v vim
snowm 7916 1 0 23:44 ? 00:00:00 ./exectest child
Note that the child process is still alive after parent process was killed. However, if I start the main process from systemd like this...
[snowm@localhost exectest]$ cat /etc/systemd/system/exectest.service
[Unit]
Description=ExecTest
[Service]
Type=simple
ExecStart=/home/snowm/src/exectest/exectest
User=snowm
[Install]
WantedBy=multi-user.target
$ sudo systemctl enable exectest
ln -s '/etc/systemd/system/exectest.service' '/etc/systemd/system/multi-user.target.wants/exectest.service'
$ sudo systemctl start exectest
... then the child also dies when I kill the main process:
$ ps -ef | grep exectest | grep -v grep | grep -v vim
snowm 8132 1 0 23:55 ? 00:00:00 /home/snowm/src/exectest/exectest
snowm 8134 8132 0 23:55 ? 00:00:00 /home/snowm/src/exectest/exectest child
$ kill -INT 8132
$ ps -ef | grep exectest | grep -v grep | grep -v vim
$
How can I make the child survive?
Running go version go1.4.2 linux/amd64 under CentOS Linux release 7.1.1503 (Core).
