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comparison pylons_app/lib/pidlock.py @ 497:fb0c3af6031b celery

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Implemented locking for task, to prevent for running the same tasks, moved out pidlock library. Added dirsize display
author Marcin Kuzminski <marcin@python-works.com>
date Thu, 23 Sep 2010 01:08:33 +0200
parents pylons_app/lib/indexers/pidlock.py@b153a51b1d3b
children d280aa1c85c6
comparison
equal deleted inserted replaced
496:47f4c7ff245b 497:fb0c3af6031b
1 import os, time
2 import sys
3 from warnings import warn
4
5 class LockHeld(Exception):pass
6
7
8 class DaemonLock(object):
9 """daemon locking
10 USAGE:
11 try:
12 l = lock()
13 main()
14 l.release()
15 except LockHeld:
16 sys.exit(1)
17 """
18
19 def __init__(self, file=None, callbackfn=None,
20 desc='daemon lock', debug=False):
21
22 self.pidfile = file if file else os.path.join(os.path.dirname(__file__),
23 'running.lock')
24 self.callbackfn = callbackfn
25 self.desc = desc
26 self.debug = debug
27 self.held = False
28 #run the lock automatically !
29 self.lock()
30
31 def __del__(self):
32 if self.held:
33
34 # warn("use lock.release instead of del lock",
35 # category = DeprecationWarning,
36 # stacklevel = 2)
37
38 # ensure the lock will be removed
39 self.release()
40
41
42 def lock(self):
43 """
44 locking function, if lock is present it will raise LockHeld exception
45 """
46 lockname = '%s' % (os.getpid())
47
48 self.trylock()
49 self.makelock(lockname, self.pidfile)
50 return True
51
52 def trylock(self):
53 running_pid = False
54 try:
55 pidfile = open(self.pidfile, "r")
56 pidfile.seek(0)
57 running_pid = pidfile.readline()
58 if self.debug:
59 print 'lock file present running_pid: %s, checking for execution'\
60 % running_pid
61 # Now we check the PID from lock file matches to the current
62 # process PID
63 if running_pid:
64 if os.path.exists("/proc/%s" % running_pid):
65 print "You already have an instance of the program running"
66 print "It is running as process %s" % running_pid
67 raise LockHeld
68 else:
69 print "Lock File is there but the program is not running"
70 print "Removing lock file for the: %s" % running_pid
71 self.release()
72 except IOError, e:
73 if e.errno != 2:
74 raise
75
76
77 def release(self):
78 """
79 releases the pid by removing the pidfile
80 """
81 if self.callbackfn:
82 #execute callback function on release
83 if self.debug:
84 print 'executing callback function %s' % self.callbackfn
85 self.callbackfn()
86 try:
87 if self.debug:
88 print 'removing pidfile %s' % self.pidfile
89 os.remove(self.pidfile)
90 self.held = False
91 except OSError, e:
92 if self.debug:
93 print 'removing pidfile failed %s' % e
94 pass
95
96 def makelock(self, lockname, pidfile):
97 """
98 this function will make an actual lock
99 @param lockname: acctual pid of file
100 @param pidfile: the file to write the pid in
101 """
102 if self.debug:
103 print 'creating a file %s and pid: %s' % (pidfile, lockname)
104 pidfile = open(self.pidfile, "wb")
105 pidfile.write(lockname)
106 pidfile.close
107 self.held = True
108
109
110 def main():
111 print 'func is running'
112 cnt = 20
113 while 1:
114 print cnt
115 if cnt == 0:
116 break
117 time.sleep(1)
118 cnt -= 1
119
120
121 if __name__ == "__main__":
122 try:
123 l = DaemonLock(desc='test lock')
124 main()
125 l.release()
126 except LockHeld:
127 sys.exit(1)