10bfa1c243
- Fix tests. - Fix empty self.keep_fds behaviour. - Add tests for self.keep_fds. - Update README.md.
129 lines
4.3 KiB
Python
129 lines
4.3 KiB
Python
# #!/usr/bin/python
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import fcntl
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import os
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import sys
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import signal
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import resource
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import logging
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import atexit
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from logging import handlers
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class Daemonize(object):
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""" Daemonize object
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Object constructor expects three arguments:
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- app: contains the application name which will be sent to syslog.
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- pid: path to the pidfile.
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- action: your custom function which will be executed after daemonization.
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- keep_fds: optional list of fds which should not be closed.
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"""
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def __init__(self, app, pid, action, keep_fds=None):
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self.app = app
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self.pid = pid
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self.action = action
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if keep_fds:
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self.keep_fds = keep_fds
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else:
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self.keep_fds = []
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# Initialize logging.
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self.logger = logging.getLogger(self.app)
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self.logger.setLevel(logging.DEBUG)
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# Display log messages only on defined handlers.
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self.logger.propagate = False
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# It will work on OS X and Linux. No FreeBSD support, guys, I don't
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# want to import re here to parse your peculiar platform string.
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if sys.platform == "darwin":
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syslog_address = "/var/run/syslog"
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else:
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syslog_address = "/dev/log"
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syslog = handlers.SysLogHandler(syslog_address)
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syslog.setLevel(logging.INFO)
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# Try to mimic to normal syslog messages.
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formatter = logging.Formatter("%(asctime)s %(name)s: %(message)s",
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"%b %e %H:%M:%S")
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syslog.setFormatter(formatter)
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self.logger.addHandler(syslog)
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def sigterm(self, signum, frame):
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""" sigterm method
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These actions will be done after SIGTERM.
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"""
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self.logger.warn("Caught signal %s. Stopping daemon." % signum)
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os.remove(self.pid)
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sys.exit(0)
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def start(self):
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""" start method
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Main daemonization process.
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"""
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# Fork, creating a new process for the child.
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process_id = os.fork()
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if process_id < 0:
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# Fork error. Exit badly.
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sys.exit(1)
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elif process_id != 0:
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# This is the parent process. Exit.
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sys.exit(0)
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# This is the child process. Continue.
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# Stop listening for signals that the parent process receives.
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# This is done by getting a new process id.
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# setpgrp() is an alternative to setsid().
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# setsid puts the process in a new parent group and detaches its
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# controlling terminal.
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process_id = os.setsid()
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if process_id == -1:
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# Uh oh, there was a problem.
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sys.exit(1)
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# Close all file descriptors, except the ones mentioned in
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# self.keep_fds.
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devnull = "/dev/null"
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if hasattr(os, "devnull"):
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# Python has set os.devnull on this system, use it instead
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# as it might be different than /dev/null.
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devnull = os.devnull
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for fd in range(resource.getrlimit(resource.RLIMIT_NOFILE)[0]):
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if fd not in self.keep_fds:
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try:
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os.close(fd)
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except OSError:
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pass
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os.open(devnull, os.O_RDWR)
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os.dup(0)
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os.dup(0)
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# Set umask to default to safe file permissions when running
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# as a root daemon. 027 is an octal number.
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os.umask(027)
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# Change to a known directory. If this isn't done, starting
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# a daemon in a subdirectory that needs to be deleted results
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# in "directory busy" errors.
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# On some systems, running with chdir("/") is not allowed,
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# so this should be settable by the user of this library.
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os.chdir("/")
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# Create a lockfile so that only one instance of this daemon
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# is running at any time.
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lockfile = open(self.pid, "w")
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# Try to get an exclusive lock on the file. This will fail
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# if another process has the file locked.
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fcntl.lockf(lockfile, fcntl.LOCK_EX | fcntl.LOCK_NB)
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# Record the process id to the lockfile. This is standard
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# practice for daemons.
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lockfile.write("%s" % (os.getpid()))
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lockfile.flush()
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# Set custom action on SIGTERM.
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signal.signal(signal.SIGTERM, self.sigterm)
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atexit.register(self.sigterm)
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self.logger.warn("Starting daemon.")
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self.action()
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