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- #!/usr/bin/env python
- import sys, os, time, atexit
- from signal import SIGTERM
- class Daemon:
- """
- A generic daemon class.
- Usage: subclass the Daemon class and override the run() method
- """
- def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
- self.stdin = stdin
- self.stdout = stdout
- self.stderr = stderr
- self.pidfile = pidfile
- def daemonize(self):
- """
- do the UNIX double-fork magic, see Stevens' "Advanced
- Programming in the UNIX Environment" for details (ISBN 0201563177)
- http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
- """
- try:
- pid = os.fork()
- if pid > 0:
- # exit first parent
- sys.exit(0)
- except OSError, e:
- sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
- sys.exit(1)
- # decouple from parent environment
- os.chdir("/")
- os.setsid()
- os.umask(0)
- # do second fork
- try:
- pid = os.fork()
- if pid > 0:
- # exit from second parent
- sys.exit(0)
- except OSError, e:
- sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
- sys.exit(1)
- # redirect standard file descriptors
- sys.stdout.flush()
- sys.stderr.flush()
- si = file(self.stdin, 'r')
- so = file(self.stdout, 'a+')
- se = file(self.stderr, 'a+', 0)
- os.dup2(si.fileno(), sys.stdin.fileno())
- os.dup2(so.fileno(), sys.stdout.fileno())
- os.dup2(se.fileno(), sys.stderr.fileno())
- # write pidfile
- atexit.register(self.delpid)
- pid = str(os.getpid())
- file(self.pidfile,'w+').write("%s\n" % pid)
- def delpid(self):
- os.remove(self.pidfile)
- def start(self):
- """
- Start the daemon
- """
- # Check for a pidfile to see if the daemon already runs
- try:
- pf = file(self.pidfile,'r')
- pid = int(pf.read().strip())
- pf.close()
- except IOError:
- pid = None
- if pid:
- message = "pidfile %s already exist. Daemon already running?\n"
- sys.stderr.write(message % self.pidfile)
- sys.exit(1)
- # Start the daemon
- self.daemonize()
- self.run()
- def stop(self):
- """
- Stop the daemon
- """
- # Get the pid from the pidfile
- try:
- pf = file(self.pidfile,'r')
- pid = int(pf.read().strip())
- pf.close()
- except IOError:
- pid = None
- if not pid:
- message = "pidfile %s does not exist. Daemon not running?\n"
- sys.stderr.write(message % self.pidfile)
- return # not an error in a restart
- # Try killing the daemon process
- try:
- while 1:
- os.kill(pid, SIGTERM)
- time.sleep(0.1)
- except OSError, err:
- err = str(err)
- if err.find("No such process") > 0:
- if os.path.exists(self.pidfile):
- os.remove(self.pidfile)
- else:
- print str(err)
- sys.exit(1)
- def restart(self):
- """
- Restart the daemon
- """
- self.stop()
- self.start()
- def run(self):
- """
- You should override this method when you subclass Daemon. It will be called after the process has been
- daemonized by start() or restart().
- """
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