154 lines
4.4 KiB
Python
154 lines
4.4 KiB
Python
# Shamelessly stolen from https://gist.github.com/josephernest/77fdb0012b72ebdf4c9d19d6256a1119
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#
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# From "A simple unix/linux daemon in Python" by Sander Marechal
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# See http://stackoverflow.com/a/473702/1422096 and
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# http://web.archive.org/web/20131017130434/http://www.jejik.com/articles/2007/02/a_simple_unix_linux_daemon_in_python/
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#
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# Modified to add quit() that allows to run some code before closing the daemon
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# See http://stackoverflow.com/a/40423758/1422096
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#
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# Modified for Python 3
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# (see also: http://web.archive.org/web/20131017130434/http://www.jejik.com/files/examples/daemon3x.py)
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#
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# Joseph Ernest, 20200507_1220
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import atexit
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import os
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import sys
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import time
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from signal import SIGTERM, signal
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class Daemon:
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"""
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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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"""
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def __init__(self, pidfile='_.pid', stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
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self.stdin = stdin
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self.stdout = stdout
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self.stderr = stderr
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self.pidfile = pidfile
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def daemonize(self):
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"""
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do the UNIX double-fork magic, see Stevens' "Advanced
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Programming in the UNIX Environment" for details (ISBN 0201563177)
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http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
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"""
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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 e:
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sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
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sys.exit(1)
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# decouple from parent environment
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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 e:
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sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
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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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atexit.register(self.onstop)
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signal(SIGTERM, lambda signum, stack_frame: exit())
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# write pidfile
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pid = str(os.getpid())
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open(self.pidfile, 'w+').write("%s\n" % pid)
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def onstop(self):
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self.quit()
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os.remove(self.pidfile)
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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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pf = open(self.pidfile, 'r')
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pid = int(pf.read().strip())
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pf.close()
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except IOError:
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pid = None
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if pid:
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message = "pidfile %s already exist. Daemon already running?\n"
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sys.stderr.write(message % self.pidfile)
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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 pidfile
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try:
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pf = open(self.pidfile, 'r')
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pid = int(pf.read().strip())
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pf.close()
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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 %s does not exist. Daemon not running?\n"
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sys.stderr.write(message % 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 1:
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os.kill(pid, SIGTERM)
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time.sleep(0.1)
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except OSError as err:
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err = str(err)
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if err.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))
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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. It will be called after the process has been
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daemonized by start() or restart().
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"""
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def quit(self):
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"""
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You should override this method when you subclass Daemon. It will be called before the process is stopped.
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"""
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