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comparison planemo/lib/python3.7/site-packages/galaxy/util/filelock.py @ 1:56ad4e20f292 draft

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"planemo upload commit 6eee67778febed82ddd413c3ca40b3183a3898f1"
author guerler
date Fri, 31 Jul 2020 00:32:28 -0400
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0:d30785e31577 1:56ad4e20f292
1 """Code obtained from https://github.com/dmfrey/FileLock.
2
3 See full license at:
4
5 https://github.com/dmfrey/FileLock/blob/master/LICENSE.txt
6
7 """
8 import errno
9 import os
10 import time
11
12
13 class FileLockException(Exception):
14 pass
15
16
17 class FileLock(object):
18 """ A file locking mechanism that has context-manager support so
19 you can use it in a with statement. This should be relatively cross
20 compatible as it doesn't rely on msvcrt or fcntl for the locking.
21 """
22
23 def __init__(self, file_name, timeout=10, delay=.05):
24 """ Prepare the file locker. Specify the file to lock and optionally
25 the maximum timeout and the delay between each attempt to lock.
26 """
27 self.is_locked = False
28 full_path = os.path.abspath(file_name)
29 self.lockfile = "%s.lock" % full_path
30 self.file_name = full_path
31 self.timeout = timeout
32 self.delay = delay
33
34 def acquire(self):
35 """ Acquire the lock, if possible. If the lock is in use, it check again
36 every `wait` seconds. It does this until it either gets the lock or
37 exceeds `timeout` number of seconds, in which case it throws
38 an exception.
39 """
40 start_time = time.time()
41 while True:
42 try:
43 self.fd = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
44 break
45 except OSError as e:
46 if e.errno != errno.EEXIST:
47 raise
48 if (time.time() - start_time) >= self.timeout:
49 raise FileLockException("Timeout occurred.")
50 time.sleep(self.delay)
51 self.is_locked = True
52
53 def release(self):
54 """ Get rid of the lock by deleting the lockfile.
55 When working in a `with` statement, this gets automatically
56 called at the end.
57 """
58 if self.is_locked:
59 os.close(self.fd)
60 os.unlink(self.lockfile)
61 self.is_locked = False
62
63 def __enter__(self):
64 """ Activated when used in the with statement.
65 Should automatically acquire a lock to be used in the with block.
66 """
67 if not self.is_locked:
68 self.acquire()
69 return self
70
71 def __exit__(self, type, value, traceback):
72 """ Activated at the end of the with statement.
73 It automatically releases the lock if it isn't locked.
74 """
75 if self.is_locked:
76 self.release()
77
78 def __del__(self):
79 """ Make sure that the FileLock instance doesn't leave a lockfile
80 lying around.
81 """
82 self.release()