如何使用python书写守护进程？daemon、python-daemon

可以参考的supervisor实现：https://github.com/Supervisor/supervisor；http://supervisord.org/configuration.html

https://www.python.org/dev/peps/pep-3143/；https://github.com/serverdensity/python-daemon

https://pypi.org/project/python-daemon/

示例：https://codeday.me/bug/20180115/119802.html

#!/usr/bin/env python3.5
import sys
import os
import time
import argparse
import logging
import daemon
from daemon import pidfile

debug_p = False

def do_something(logf):
    ### This does the "work" of the daemon

    logger = logging.getLogger('eg_daemon')
    logger.setLevel(logging.INFO)

    fh = logging.FileHandler(logf)
    fh.setLevel(logging.INFO)

    formatstr = '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
    formatter = logging.Formatter(formatstr)

    fh.setFormatter(formatter)

    logger.addHandler(fh)

    while True:
        logger.debug("this is a DEBUG message")
        logger.info("this is an INFO message")
        logger.error("this is an ERROR message")
        time.sleep(5)


def start_daemon(pidf, logf):
    ### This launches the daemon in its context

    ### XXX pidfile is a context
    with daemon.DaemonContext(
        working_directory='/var/lib/eg_daemon',
        umask=0o002,
        pidfile=pidfile.TimeoutPIDLockFile(pidf),
        ) as context:
        do_something(logf)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Example daemon in Python")
    parser.add_argument('-p', '--pid-file', default='/var/run/eg_daemon.pid')
    parser.add_argument('-l', '--log-file', default='/var/log/eg_daemon.log')

    args = parser.parse_args()

    start_daemon(pidf=args.pid_file, logf=args.log_file)

和相应的脚本：

#!/bin/bash
#
# eg_daemon      Startup script for eg_daemon
#
# chkconfig: - 87 12
# description: eg_daemon is a dummy Python-based daemon
# config: /etc/eg_daemon/eg_daemon.conf
# config: /etc/sysconfig/eg_daemon
# pidfile: /var/run/eg_daemon.pid
#
### BEGIN INIT INFO
# Provides: eg_daemon
# Required-Start: $local_fs
# Required-Stop: $local_fs
# Short-Description: start and stop eg_daemon server
# Description: eg_daemon is a dummy Python-based daemon
### END INIT INFO

# Source function library.
. /etc/rc.d/init.d/functions

if [ -f /etc/sysconfig/eg_daemon ]; then
        . /etc/sysconfig/eg_daemon
fi

eg_daemon=/var/lib/eg_daemon/eg_daemon.py
prog=eg_daemon
pidfile=${PIDFILE-/var/run/eg_daemon.pid}
logfile=${LOGFILE-/var/log/eg_daemon.log}
RETVAL=0

OPTIONS=""

start() {
        echo -n $"Starting $prog: "

        if [[ -f ${pidfile} ]] ; then
            pid=$( cat $pidfile  )
            isrunning=$( ps -elf | grep  $pid | grep $prog | grep -v grep )

            if [[ -n ${isrunning} ]] ; then
                echo $"$prog already running"
                return 0
            fi
        fi
        $eg_daemon -p $pidfile -l $logfile $OPTIONS
        RETVAL=$?
        [ $RETVAL = 0 ] && success || failure
        echo
        return $RETVAL
}

stop() {
    if [[ -f ${pidfile} ]] ; then
        pid=$( cat $pidfile )
        isrunning=$( ps -elf | grep $pid | grep $prog | grep -v grep | awk '{print $4}' )

        if [[ ${isrunning} -eq ${pid} ]] ; then
            echo -n $"Stopping $prog: "
            kill $pid
        else
            echo -n $"Stopping $prog: "
            success
        fi
        RETVAL=$?
    fi
    echo
    return $RETVAL
}

reload() {
    echo -n $"Reloading $prog: "
    echo
}

# See how we were called.
case "$1" in
  start)
    start
    ;;
  stop)
    stop
    ;;
  status)
    status -p $pidfile $eg_daemon
    RETVAL=$?
    ;;
  restart)
    stop
    start
    ;;
  force-reload|reload)
    reload
    ;;
  *)
    echo $"Usage: $prog {start|stop|restart|force-reload|reload|status}"
    RETVAL=2
esac

exit $RETVAL