python - 启动我的守护进程时 Systemctl 阻塞

Question

我用 Python 写了一个小守护进程:

#!/usr/bin/python3

import time
import click
import daemonocle

from daemonocle.cli import DaemonCLI

@click.command(cls=DaemonCLI, daemon_params={'pidfile': '/var/run/daemon.pid'})
def main():
    while True:
        time.sleep(3)

if __name__ == '__main__':
    main()

它的效果很好。如果我执行以下操作，我将获得良好的退出状态 0

$ sudo ./daemon start 
Starting daemon ... OK    

$ echo $?
0

然后我写了一个systemd服务文件:

[Unit]
SourcePath=/home/pi/daemon/daemon
Description=My First Daemon
Before=multi-user.target
After=mosquitto.target

[Service]
Type=forking
PIDFile=/var/run/daemon.pid
Restart=no
ExecStart=/home/pi/daemon/daemon start
ExecStop=/home/pi/daemon/daemon stop
ExecReload=/home/pi/daemon/daemon reload

如果我尝试使用 systemctl 运行我的守护进程，该命令仍然处于阻塞状态:

$ sudo systemctl start daemon
^C
$ sudo systemctl status daemon
? daemon.service - XEMWAY Demo Service
   Loaded: loaded (/home/pi/daemon/daemon; static; vendor preset: enabled)
   Active: activating (start) since Wed 2019-02-13 13:47:40 GMT; 12s ago
  Process: 13044 ExecStop=/home/pi/daemon/daemon stop (code=exited, status=0/SUCCESS)
 Main PID: 12304 (code=exited, status=143); Control PID: 13079 (daemon)
   CGroup: /system.slice/daemon.service
           +-13079 /usr/bin/python3 /home/pi/daemon/daemon start
           +-13081 /usr/bin/python3 /home/pi/daemon/daemon start

一分钟后 systemd 说:

2 月 13 日 13:49:10 raspberrypi systemd[1]:daemon.service:单元进入失败状态。2 月 13 日 13:49:10 raspberrypi systemd[1]:daemon.service:失败，结果为“超时”。

这是怎么回事？

Answer 1

问题是您的服务会自行创建守护进程，而 systemd 并不知道。它只是一个简单的程序，在 systemd 的少量时间后运行并退出。而不是 forking 你想使用 simple:

Type=simple

Systemd 仍然会作为守护进程跟踪您的进程，因为它知道它的 pid:

systemctl status test2.service

* test2.service - My First Daemon
   Loaded: loaded (/tmp/a.py; static; vendor preset: disabled)
   Active: active (running) since Wed 2019-02-13 16:06:27 EET; 5s ago
 Main PID: 18104 (python)
    Tasks: 2 (limit: 4915)
   Memory: 10.1M
   CGroup: /system.slice/test2.service
           |-18104 /usr/bin/python /tmp/a.py start
           `-18115 /usr/bin/python /tmp/a.py start