Daemonize

A little tech talk for rannts#16 meetup on correct daemonization in UNIXes before systed era

Transcript

1. Правильная демонизация
   Сергей Архипов, 2017
   

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2. Чего хотим
   #!/usr/bin/env python3
   # -*- coding: utf-8 -*-
   import contextlib
   import syslog
   import time
   @contextlib.contextmanager
   def daemonize():
   yield
   if __name__ == "__main__":
   with daemonize():
   syslog.openlog(facility=syslog.LOG_USER)
   syslog.syslog("Daemon start.")
   time.sleep(10)
   syslog.syslog("Daemon done.")
   

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3. Подход 1
   def daemonize():
   first_pid = os.fork()
   if first_pid:
   sys.exit(0)
   yield
   

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4. Подход 2
   def daemonize():
   first_pid = os.fork()
   if first_pid:
   sys.exit(0)
   syslog.syslog("Session={0}, Group={1}, Parent={2},
   Self={3}".format(
   os.getsid(0), os.getpgid(0), os.getppid(),
   os.getpid()
   ))
   yield
   … Session=7087, Group=14115, Parent=14115, Self=14151
   … Daemon start.
   … Daemon done.
   

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5. Подход 2
   def daemonize():
   first_pid = os.fork()
   if first_pid:
   sys.exit(0)
   syslog.syslog("Session={0}, Group={1}, Parent={2}, Self={3}".format(
   os.getsid(0), os.getpgid(0),
   os.getppid(), os.getpid()
   ))
   os.setsid()
   syslog.syslog("Session={0}, Group={1}, Parent={2}, Self={3}".format(
   os.getsid(0), os.getpgid(0),
   os.getppid(), os.getpid()
   ))
   yield
   … Session=7087, Group=17364, Parent=17364, Self=17400
   … Session=17400, Group=17400, Parent=17364, Self=17400
   … Daemon start
   … Daemon done.
   

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6. Подход 3
   def daemonize():
   if os.fork():
   sys.exit(0)
   os.setsid()
   if os.fork():
   sys.exit(0)
   yield
   

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7. Подход 4
   def daemonize():
   if os.fork():
   sys.exit(0)
   os.setsid()
   if os.fork():
   sys.exit(0)
   os.chdir("/")
   os.umask(0o002)
   yield
   

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8. Подход 5
   def daemonize():
   if os.fork():
   sys.exit(0)
   os.setsid()
   if os.fork():
   sys.exit(0)
   os.chdir("/")
   os.umask(0o002)
   sys.stdout.flush()
   sys.stderr.flush()
   _, max_fds = resource.getrlimit(resource.RLIMIT_NOFILE)
   max_fds = max_fds if max_fds!=resource.RLIM_INFINITY else 1024
   os.closerange(0, max_fds)
   sys.stdout = sys.stderr = open(os.devnull, "w")
   sys.stdin = open(os.devnull, "r")
   yield
   

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9. Подход 6
   def daemonize():
   if os.getppid() != 1:
   return
   if os.fork():
   sys.exit(0)
   os.setsid()
   if os.fork():
   sys.exit(0)
   os.chdir("/")
   os.umask(0o002)
   sys.stdout.flush()
   sys.stderr.flush()
   _, max_fds = resource.getrlimit(resource.RLIMIT_NOFILE)
   max_fds = max_fds if max_fds != resource.RLIM_INFINITY else 1024
   os.closerange(0, max_fds)
   sys.stdout = sys.stderr = open(os.devnull, "w")
   sys.stdin = open(os.devnull, "r")
   yield
   

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10. def daemonize():
    if os.getppid() != 1:
    return
    if os.fork():
    sys.exit(0)
    os.setsid()
    if os.fork():
    sys.exit(0)
    os.chdir("/")
    os.umask(0o002)
    sys.stdout.flush()
    sys.stderr.flush()
    _, max_fds = resource.getrlimit(resource.RLIMIT_NOFILE)
    max_fds = max_fds if max_fds != resource.RLIM_INFINITY else 1024
    os.closerange(0, max_fds)
    sys.stdout = sys.stderr = open(os.devnull, "w")
    sys.stdin = open(os.devnull, "r")
    yield
    

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