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Source code for luxon.utils.daemon

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import sys
import os
import time
import atexit
from signal import SIGTERM


[docs]class Daemon(object): """Generic Daemon class. Usage options: 1. Use as context with Daemon: 2. Subclass the Daemon class and override the run() method 3. Define method to run via keyword arguements. """ def __init__(self, pidfile, run=None, args=[], kwargs={}, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'): self.stdin = stdin self.stdout = stdout self.stderr = stderr self.pidfile = pidfile self._run = run self._args = args self._kwargs = kwargs def _daemonize(self): """Daemonize Process 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 """ # Do the first fork try: pid = os.fork() if pid > 0: # Exit first parent sys.exit(0) except OSError as 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 the second fork try: pid = os.fork() if pid > 0: # Exit from second parent sys.exit(0) except OSError as 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 = open(self.stdin, 'r') so = open(self.stdout, 'wb', 0) se = open(self.stderr, 'wb', 0) os.dup2(si.fileno(), sys.stdin.fileno()) os.dup2(so.fileno(), sys.stdout.fileno()) os.dup2(se.fileno(), sys.stderr.fileno()) self.write_pid() def write_pid(self): # Write PID File atexit.register(self.delete_pid) pid = str(os.getpid()) open(self.pidfile, 'w+').write("%s\n" % pid) def delete_pid(self): try: os.remove(self.pidfile) except FileNotFoundError: pass
[docs] def daemonize(self): """Start the daemon """ # Check for a Pid File to see if the daemon is already running. try: pf = open(self.pidfile, 'r') pid = int(pf.read().strip()) pf.close() except IOError: pid = None if pid: try: os.kill(pid, 0) message = "running pid %s and pidfile %s already exist." +\ " Daemon already running?\n" sys.stderr.write(message % (pid, self.pidfile)) sys.exit(1) return False except OSError: pid = None # Start the daemon. self._daemonize()
def start(self, fork=True): if fork is True: self.daemonize() else: if self.running: pid = str(os.getpid()) message = "running pid %s and pidfile %s already exist." +\ " Daemon already running?\n" sys.stderr.write(message % (pid, self.pidfile)) exit() self.write_pid() self.run()
[docs] def stop(self): """Stop the daemon """ # Get the pid from the Pid File. try: pf = open(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 # Try killing the daemon process. try: while 1: os.kill(pid, SIGTERM) time.sleep(0.1) except OSError as 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)
@property def running(self): try: pf = open(self.pidfile, 'r') pid = int(pf.read().strip()) pf.close() except IOError: return False try: os.kill(pid, 0) return True except OSError: return False @property def get_pid(self): if self.running: try: pf = open(self.pidfile, 'r') pid = int(pf.read().strip()) pf.close() return pid except IOError: pass return None
[docs] def restart(self): """Restart the daemon """ self.stop() self.start()
def __enter__(self): self.daemonize() def __exit__(self, type, value, traceback): self.delete_pid()
[docs] def run(self): """Method to run daemonized You should override this method when you subclass Daemon. It will be called after the process has been daemonized by start() or restart(). """ if self._run is not None: self._run(*self._args, **self._kwargs) else: raise NotImplementedError('No run method defined or run ' + ' function provided')