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python守护进程demo

2020-10-31 55 10/31

代码网上copy的,原理基本一致。

还有一个daemon的模块python-daemon,基于PEP 3143,直接封装好了守护进程需要实现的方法,推荐使用!安装命令:

pip install python-daemon

使用方法

#! /usr/bin/env python
# -*- coding: utf-8 -*-
import logging
import time
# third party libs
from daemon import runner
class Updater():
    def __init__(self):
        self.stdin_path = '/dev/null'
        self.stdout_path = '/dev/tty'
        self.stderr_path = '/dev/tty'
        self.pidfile_path = '/tmp/testdaemon.pid'
        self.pidfile_timeout = 5
    def run(self):
        while True:
            # Main code goes here ...
            # Note that logger level needs to be set to logging.DEBUG before this shows up in the logs
            logger.debug("Debug message")
            logger.info("Info message")
            logger.warn("Warning message")
            logger.error("Error message")
            time.sleep(10)
app = Updater()
logger = logging.getLogger("DaemonLog")
logger.setLevel(logging.INFO)
formatter = logging.Formatter("%(asctime)s - %(name)s - %(levelname)s - %(message)s")
handler = logging.FileHandler("/tmp/testdaemon.log")
handler.setFormatter(formatter)
logger.addHandler(handler)
daemon_runner = runner.DaemonRunner(app)
# This ensures that the logger file handle does not get closed during daemonization
daemon_runner.daemon_context.files_preserve = [handler.stream]
daemon_runner.do_action()

python2 的实现

#!/usr/bin/env python
import sys, os, time, atexit
from signal import SIGTERM
class Daemon:
    """
    A generic daemon class.
    Usage: subclass the Daemon class and override the run() method
    """
    def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
        self.stdin = stdin
        self.stdout = stdout
        self.stderr = stderr
        self.pidfile = pidfile
    def daemonize(self):
        """
        do the UNIX double-fork magic, see Stevens' "Advanced
        Programming in the UNIX Environment" for details (ISBN 0201563177)
        http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
        """
        try:
            pid = os.fork()
            if pid > 0:
                # exit first parent
                sys.exit(0)
        except OSError, e:
            sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
            sys.exit(1)
        # decouple from parent environment
        os.chdir("/")
        os.setsid()
        os.umask(0)
        # do second fork
        try:
            pid = os.fork()
            if pid > 0:
                # exit from second parent
                sys.exit(0)
        except OSError, e:
            sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
            sys.exit(1)
        # redirect standard file descriptors
        sys.stdout.flush()
        sys.stderr.flush()
        si = file(self.stdin, 'r')
        so = file(self.stdout, 'a+')
        se = file(self.stderr, 'a+', 0)
        os.dup2(si.fileno(), sys.stdin.fileno())
        os.dup2(so.fileno(), sys.stdout.fileno())
        os.dup2(se.fileno(), sys.stderr.fileno())
        # write pidfile
        atexit.register(self.delpid)
        pid = str(os.getpid())
        file(self.pidfile, 'w+').write("%s\n" % pid)
    def delpid(self):
        os.remove(self.pidfile)
    def start(self):
        """
        Start the daemon
        """
        # Check for a pidfile to see if the daemon already runs
        try:
            pf = file(self.pidfile, 'r')
            pid = int(pf.read().strip())
            pf.close()
        except IOError:
            pid = None
        if pid:
            message = "pidfile %s already exist. Daemon already running?\n"
            sys.stderr.write(message % self.pidfile)
            sys.exit(1)
        # Start the daemon
        self.daemonize()
        self.run()
    def stop(self):
        """
        Stop the daemon
        """
        # Get the pid from the pidfile
        try:
            pf = file(self.pidfile, 'r')
            pid = int(pf.read().strip())
            pf.close()
        except IOError:
            pid = None
        if not pid:
            message = "pidfile %s does not exist. Daemon not running?\n"
            sys.stderr.write(message % self.pidfile)
            return  # not an error in a restart
        # Try killing the daemon process
        try:
            while 1:
                os.kill(pid, SIGTERM)
                time.sleep(0.1)
        except OSError, err:
            err = str(err)
            if err.find("No such process") > 0:
                if os.path.exists(self.pidfile):
                    os.remove(self.pidfile)
            else:
                print str(err)
                sys.exit(1)
    def restart(self):
        """
        Restart the daemon
        """
        self.stop()
        self.start()
    def run(self):
        """
        You should override this method when you subclass Daemon. It will be called after the process has been
        daemonized by start() or restart().
        """

守护进程写法

#!/usr/bin/env python
import sys, time
from daemon import Daemon
class MyDaemon(Daemon):
    def run(self):
        while True:
            time.sleep(1)
if __name__ == "__main__":
    daemon = MyDaemon('/tmp/daemon-example.pid')
    if len(sys.argv) == 2:
        if 'start' == sys.argv[1]:
            daemon.start()
        elif 'stop' == sys.argv[1]:
            daemon.stop()
        elif 'restart' == sys.argv[1]:
            daemon.restart()
        else:
            print "Unknown command"
            sys.exit(2)
        sys.exit(0)
    else:
        print "usage: %s start|stop|restart" % sys.argv[0]
        sys.exit(2)

python3 的实现

"""Generic linux daemon base class for python 3.x."""
import sys, os, time, atexit, signal
class daemon:
    """A generic daemon class.
    Usage: subclass the daemon class and override the run() method."""
    def __init__(self, pidfile): self.pidfile = pidfile
    def daemonize(self):
        """Deamonize class. UNIX double fork mechanism."""
        try:
            pid = os.fork()
            if pid > 0:
                # exit first parent
                sys.exit(0)
        except OSError as err:
            sys.stderr.write('fork #1 failed: {0}\n'.format(err))
            sys.exit(1)
        # decouple from parent environment
        os.chdir('/')
        os.setsid()
        os.umask(0)
        # do second fork
        try:
            pid = os.fork()
            if pid > 0:
                # exit from second parent
                sys.exit(0)
        except OSError as err:
            sys.stderr.write('fork #2 failed: {0}\n'.format(err))
            sys.exit(1)
        # redirect standard file descriptors
        sys.stdout.flush()
        sys.stderr.flush()
        si = open(os.devnull, 'r')
        so = open(os.devnull, 'a+')
        se = open(os.devnull, 'a+')
        os.dup2(si.fileno(), sys.stdin.fileno())
        os.dup2(so.fileno(), sys.stdout.fileno())
        os.dup2(se.fileno(), sys.stderr.fileno())
        # write pidfile
        atexit.register(self.delpid)
        pid = str(os.getpid())
        with open(self.pidfile,'w+') as f:
            f.write(pid + '\n')
    def delpid(self):
        os.remove(self.pidfile)
    def start(self):
        """Start the daemon."""
        # Check for a pidfile to see if the daemon already runs
        try:
            with open(self.pidfile,'r') as pf:
                pid = int(pf.read().strip())
        except IOError:
            pid = None
        if pid:
            message = "pidfile {0} already exist. " + \
                    "Daemon already running?\n"
            sys.stderr.write(message.format(self.pidfile))
            sys.exit(1)
        # Start the daemon
        self.daemonize()
        self.run()
    def stop(self):
        """Stop the daemon."""
        # Get the pid from the pidfile
        try:
            with open(self.pidfile,'r') as pf:
                pid = int(pf.read().strip())
        except IOError:
            pid = None
        if not pid:
            message = "pidfile {0} does not exist. " + \
                    "Daemon not running?\n"
            sys.stderr.write(message.format(self.pidfile))
            return # not an error in a restart
        # Try killing the daemon process
        try:
            while 1:
                os.kill(pid, signal.SIGTERM)
                time.sleep(0.1)
        except OSError as err:
            e = str(err.args)
            if e.find("No such process") > 0:
                if os.path.exists(self.pidfile):
                    os.remove(self.pidfile)
            else:
                print (str(err.args))
                sys.exit(1)
    def restart(self):
        """Restart the daemon."""
        self.stop()
        self.start()
    def run(self):
        """You should override this method when you subclass Daemon.
        It will be called after the process has been daemonized by
        start() or restart()."""

A simple unix/linux daemon in Python
12.14 在Unix系统上面启动守护进程

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