139 lines
3.7 KiB
Python
139 lines
3.7 KiB
Python
#!/usr/bin/env python3
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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
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class BaseDaemon(object):
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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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startmsg = 'started with pid %s'
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def __init__(self, pidfile, 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.chdir('.')
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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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si = open(self.stdin, 'r')
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so = open(self.stdout, 'a+')
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se = open(self.stderr, 'a+')
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pid = str(os.getpid())
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sys.stderr.write("\n%s\n" % self.startmsg % pid)
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sys.stderr.flush()
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if self.pidfile:
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open(self.pidfile, 'w+').write("%s\n" % pid)
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atexit.register(self.delpid)
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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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def delpid(self):
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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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