156 lines
4.5 KiB
Python
156 lines
4.5 KiB
Python
# Copyright (c) 2022 Johannes Findeisen <you@hanez.org>
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is furnished
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# to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice (including the next
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# paragraph) shall be included in all copies or substantial portions of the
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# Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
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# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
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# OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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import atexit
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import os
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import signal
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import sys
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import time
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from logging import getLogger
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logger = getLogger(__name__)
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class Daemon:
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"""
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Usage: subclass the daemon class and override the run() method.
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"""
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def __init__(self, pid_file):
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self.pid_file = pid_file
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def daemonize(self):
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"""
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Daemonize the class using the UNIX double fork mechanism.
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"""
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# Do first 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 first parent
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sys.exit(0)
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except OSError as err:
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logger.error(str("fork #1 failed: {0}".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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logger.error(str("fork #2 failed: {0}".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.del_pid)
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pid = str(os.getpid())
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with open(self.pid_file, 'w+') as f:
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f.write(pid + '\n')
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def del_pid(self):
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os.remove(self.pid_file)
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def start(self):
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"""
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Start the daemon.
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"""
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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.pid_file, '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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message = "pid_file {0} already exist. daemon already running?"
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logger.error(str(message.format(self.pid_file)))
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sys.exit(1)
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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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"""
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Stop the daemon.
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"""
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# Get the pid from the pid_file
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try:
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with open(self.pid_file, '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 = "pid_file {0} does not exist. daemon not running?"
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logger.error(str(message.format(self.pid_file)))
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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 1:
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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.pid_file):
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os.remove(self.pid_file)
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else:
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logger.error(str(err.args))
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sys.exit(1)
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def restart(self):
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"""
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Restart the daemon.
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"""
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self.stop()
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self.start()
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def run(self):
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"""
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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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"""
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