1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
|
import os
import time
class FileBaton:
'''A primitive, file-based synchronization utility.'''
def __init__(self, lock_file_path, wait_seconds=0.1):
'''
Creates a new :class:`FileBaton`.
Args:
lock_file_path: The path to the file used for locking.
wait_seconds: The seconds to periorically sleep (spin) when
calling ``wait()``.
'''
self.lock_file_path = lock_file_path
self.wait_seconds = wait_seconds
self.fd = None
def try_acquire(self):
'''
Tries to atomically create a file under exclusive access.
Returns:
True if the file could be created, else False.
'''
try:
self.fd = os.open(self.lock_file_path, os.O_CREAT | os.O_EXCL)
return True
except FileExistsError:
return False
def wait(self):
'''
Periodically sleeps for a certain amount until the baton is released.
The amount of time slept depends on the ``wait_seconds`` parameter
passed to the constructor.
'''
while os.path.exists(self.lock_file_path):
time.sleep(self.wait_seconds)
def release(self):
'''Releases the baton and removes its file.'''
if self.fd is not None:
os.close(self.fd)
os.remove(self.lock_file_path)
|
