initdaemon.py

#!/usr/bin/python
import sys
import os
import time
import atexit
import threading
from signal import SIGTERM


class Daemon():
    """
    A generic daemon class.
    Usage: subclass the Daemon class and override the _run() method
    """
    def __init__(self, pidfile='/tmp/client.pid', stdin='/dev/null',
                 stdout='/dev/null', stderr='/dev/null'):
        self.stdin = stdin
        self.stdout = stdout
        self.stderr = stderr
        self.pidfile = pidfile

    def _daemonize(self):
        try:
            pid = os.fork()
            if pid > 0:
                sys.exit(0)
        except OSError, e:
            sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno,
                             e.strerror))
            sys.exit(1)
        os.setsid()
        os.chdir("/")
        os.umask(0)
        try:
            pid = os.fork()
            if pid > 0:
                sys.exit(0)
        except OSError, e:
            sys.stderr.write("fork #2 failed: %d (%s)\n" %
                             (e.errno, e.strerror))
            sys.exit(1)
    # 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())
        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 kill_pid(self, pid):
        try:
            while 1:
                os.kill(pid, SIGTERM)
                time.sleep(0.1)
        except OSError, err:
            err = str(err)
            if err.find("No such process") > 0:
                pass
            else:
                print str(err)
                sys.exit(1)

    def stop(self):
        """
        Stop the daemon
        """
        # Get the pid from the pidfile
        try:
            pf = file(self.pidfile, 'r')
            pidlist = list(pf)
            pf.close()
        except IOError:
            pidlist = None
        if not pidlist:
            message = "pidfile %s does not exist. Daemon not running?\n"
            sys.stderr.write(message % self.pidfile)
            return  # not an error in a restart
        for pid in pidlist:
            self.kill_pid(int(pid.strip('\n')))
        self.delpid()

    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().
        """
'''
class MyDaemon(Daemon):
    def _run(self):
        while True:
            time.sleep(1)
if __name__ == "__main__":
    daemon = MyDaemon('/tmp/daemon.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)
'''