| 1 | #!/usr/bin/env python
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| 2 |
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| 3 | import sys, os, time, atexit
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| 4 | from signal import SIGTERM
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| 5 |
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| 6 | class Daemon:
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| 7 | """
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| 8 | A generic daemon class.
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| 9 |
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| 10 | Usage: subclass the Daemon class and override the run() method
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| 11 | """
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| 12 | def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
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| 13 | self.stdin = stdin
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| 14 | self.stdout = stdout
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| 15 | self.stderr = stderr
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| 16 | self.pidfile = pidfile
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| 17 |
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| 18 | def daemonize(self):
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| 19 | """
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| 20 | do the UNIX double-fork magic, see Stevens' "Advanced
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| 21 | Programming in the UNIX Environment" for details (ISBN 0201563177)
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| 22 | http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
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| 23 | """
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| 24 | try:
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| 25 | pid = os.fork()
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| 26 | if pid > 0:
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| 27 | # exit first parent
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| 28 | sys.exit(0)
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| 29 | except OSError, e:
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| 30 | sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
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| 31 | sys.exit(1)
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| 32 |
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| 33 | # decouple from parent environment
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| 34 | os.chdir("/")
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| 35 | os.setsid()
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| 36 | os.umask(0)
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| 37 |
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| 38 | # do second fork
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| 39 | try:
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| 40 | pid = os.fork()
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| 41 | if pid > 0:
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| 42 | # exit from second parent
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| 43 | sys.exit(0)
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| 44 | except OSError, e:
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| 45 | sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
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| 46 | sys.exit(1)
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| 47 |
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| 48 | # redirect standard file descriptors
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| 49 | sys.stdout.flush()
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| 50 | sys.stderr.flush()
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| 51 | si = file(self.stdin, 'r')
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| 52 | so = file(self.stdout, 'a+')
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| 53 | se = file(self.stderr, 'a+', 0)
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| 54 | os.dup2(si.fileno(), sys.stdin.fileno())
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| 55 | os.dup2(so.fileno(), sys.stdout.fileno())
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| 56 | os.dup2(se.fileno(), sys.stderr.fileno())
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| 57 |
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| 58 | # write pidfile
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| 59 | atexit.register(self.delpid)
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| 60 | pid = str(os.getpid())
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| 61 | file(self.pidfile,'w+').write("%s\n" % pid)
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| 62 |
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| 63 | def delpid(self):
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| 64 | os.remove(self.pidfile)
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| 65 |
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| 66 | def start(self):
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| 67 | """
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| 68 | Start the daemon
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| 69 | """
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| 70 | # Check for a pidfile to see if the daemon already runs
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| 71 | try:
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| 72 | pf = file(self.pidfile,'r')
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| 73 | pid = int(pf.read().strip())
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| 74 | pf.close()
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| 75 | except IOError:
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| 76 | pid = None
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| 77 |
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| 78 | if pid:
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| 79 | message = "pidfile %s already exist. Daemon already running?\n"
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| 80 | sys.stderr.write(message % self.pidfile)
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| 81 | sys.exit(1)
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| 82 |
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| 83 | # Start the daemon
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| 84 | self.daemonize()
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| 85 | self.run()
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| 86 |
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| 87 | def stop(self):
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| 88 | """
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| 89 | Stop the daemon
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| 90 | """
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| 91 | # Get the pid from the pidfile
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| 92 | try:
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| 93 | pf = file(self.pidfile,'r')
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| 94 | pid = int(pf.read().strip())
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| 95 | pf.close()
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| 96 | except IOError:
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| 97 | pid = None
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| 98 |
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| 99 | if not pid:
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| 100 | message = "pidfile %s does not exist. Daemon not running?\n"
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| 101 | sys.stderr.write(message % self.pidfile)
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| 102 | return # not an error in a restart
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| 103 |
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| 104 | # Try killing the daemon process
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| 105 | try:
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| 106 | while 1:
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| 107 | os.kill(pid, SIGTERM)
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| 108 | time.sleep(0.1)
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| 109 | except OSError, err:
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| 110 | err = str(err)
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| 111 | if err.find("No such process") > 0:
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| 112 | if os.path.exists(self.pidfile):
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| 113 | os.remove(self.pidfile)
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| 114 | else:
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| 115 | print str(err)
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| 116 | sys.exit(1)
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| 117 |
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| 118 | def restart(self):
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| 119 | """
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| 120 | Restart the daemon
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| 121 | """
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| 122 | self.stop()
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| 123 | self.start()
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| 124 |
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| 125 | def run(self):
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| 126 | """
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| 127 | You should override this method when you subclass Daemon. It will be called after the process has been
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| 128 | daemonized by start() or restart().
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| 129 | """
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