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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Example on how to create a daemon.
If you are confused on how the daemon library works you can get some ideas
from the tests.
https://pagure.io/python-daemon/blob/master/f/test/test_runner.py
"""
import os
import sys
from logging import FileHandler, Formatter, getLogger, info
from os.path import isfile
from signal import SIGINT, SIGTERM, signal
from time import sleep
class MyDaemon(object):
"""Daemon class. Not for production use, example only."""
def __init__(self):
"""Initialize the paths and the pidfile of the daemon."""
# Setup logging
log = getLogger()
handler = FileHandler('/var/log/python_daemon.log')
formatter = Formatter('%(asctime)s %(levelname)s %(message)s')
handler.setFormatter(formatter)
log.addHandler(handler)
log.setLevel('INFO')
self.pidfile_path = '/var/run/python_daemon.pid'
# Register handlers to exit when we get a kill signal
signal(SIGINT, self.exit_gracefully)
signal(SIGTERM, self.exit_gracefully)
def exit_gracefully(self, signum, frame):
"""Exit Gracefully."""
info('I died')
self.remove_pidfile()
exit()
def create_pidfile(self):
"""Create a pidfile for the daemon."""
info('Creating pid file')
with open(self.pidfile_path, mode='w', encoding='utf-8') as a_file:
a_file.write(str('{}\n'.format(self.pid)))
def remove_pidfile(self):
"""Remove the pidfile."""
info('Removing pidfile: {}'.format(self.pidfile_path))
os.remove(self.pidfile_path)
def detach_process(self):
"""Simple method for daemonizing process."""
newpid = os.fork()
if newpid > 0:
exit()
else:
os.setsid()
newpid = os.fork()
if newpid > 0:
exit()
else:
self.pid = os.getpid()
return
def run(self):
"""Entrypoint for the daemon."""
if isfile(self.pidfile_path):
print('Pidfile already exists, Daemon already running')
exit()
info('Starting up the python daemon.')
self.detach_process()
# redirect stdin, stdout and stderr to devnull
f = open(os.devnull, 'w')
sys.stdin = f
sys.stdout = f
sys.stderr = f
# Create the pid file
self.create_pidfile()
while True:
info('I am alive')
sleep(1)
def stop(self):
"""Stop a currently running process."""
try:
with open(self.pidfile_path, encoding='utf-8') as a_file:
pid = a_file.readline()
pid = pid.strip() # Remove whitespace
os.kill(int(pid), SIGTERM)
exit()
except FileNotFoundError:
print('no pidfile found, is the daemon running?')
exit()
# run the daemon
if __name__ == '__main__':
daemon = MyDaemon()
if len(sys.argv) <= 1:
print('Usage: ./daemon_example.py \'start|stop\'')
exit()
if sys.argv[1] == 'start':
daemon.run()
exit()
if sys.argv[1] == 'stop':
daemon.stop()
exit()
print('Error: I dont know that command')
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