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