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annotate env/lib/python3.7/site-packages/galaxy/util/filelock.py @ 3:758bc20232e8 draft

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"planemo upload commit 2a0fe2cc28b09e101d37293e53e82f61762262ec"
author shellac
date Thu, 14 May 2020 16:20:52 -0400
parents 26e78fe6e8c4
children
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1 """Code obtained from https://github.com/dmfrey/FileLock.
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2
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3 See full license at:
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4
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5 https://github.com/dmfrey/FileLock/blob/master/LICENSE.txt
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6
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7 """
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8 import errno
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9 import os
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10 import time
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11
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12
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13 class FileLockException(Exception):
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14 pass
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15
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16
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17 class FileLock(object):
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18 """ A file locking mechanism that has context-manager support so
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19 you can use it in a with statement. This should be relatively cross
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20 compatible as it doesn't rely on msvcrt or fcntl for the locking.
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21 """
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22
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23 def __init__(self, file_name, timeout=10, delay=.05):
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24 """ Prepare the file locker. Specify the file to lock and optionally
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25 the maximum timeout and the delay between each attempt to lock.
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26 """
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27 self.is_locked = False
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28 full_path = os.path.abspath(file_name)
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29 self.lockfile = "%s.lock" % full_path
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30 self.file_name = full_path
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31 self.timeout = timeout
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32 self.delay = delay
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33
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34 def acquire(self):
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35 """ Acquire the lock, if possible. If the lock is in use, it check again
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36 every `wait` seconds. It does this until it either gets the lock or
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37 exceeds `timeout` number of seconds, in which case it throws
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38 an exception.
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39 """
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40 start_time = time.time()
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41 while True:
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42 try:
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43 self.fd = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
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44 break
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45 except OSError as e:
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46 if e.errno != errno.EEXIST:
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47 raise
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48 if (time.time() - start_time) >= self.timeout:
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49 raise FileLockException("Timeout occurred.")
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50 time.sleep(self.delay)
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51 self.is_locked = True
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52
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53 def release(self):
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54 """ Get rid of the lock by deleting the lockfile.
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55 When working in a `with` statement, this gets automatically
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56 called at the end.
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57 """
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58 if self.is_locked:
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59 os.close(self.fd)
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60 os.unlink(self.lockfile)
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61 self.is_locked = False
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62
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63 def __enter__(self):
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64 """ Activated when used in the with statement.
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65 Should automatically acquire a lock to be used in the with block.
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66 """
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67 if not self.is_locked:
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68 self.acquire()
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69 return self
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70
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71 def __exit__(self, type, value, traceback):
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72 """ Activated at the end of the with statement.
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73 It automatically releases the lock if it isn't locked.
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74 """
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75 if self.is_locked:
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76 self.release()
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77
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78 def __del__(self):
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79 """ Make sure that the FileLock instance doesn't leave a lockfile
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80 lying around.
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81 """
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82 self.release()