Mercurial > repos > shellac > guppy_basecaller
annotate env/lib/python3.7/site-packages/lockfile/symlinklockfile.py @ 0:26e78fe6e8c4 draft
"planemo upload commit c699937486c35866861690329de38ec1a5d9f783"
author | shellac |
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date | Sat, 02 May 2020 07:14:21 -0400 |
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1 from __future__ import absolute_import |
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2 |
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3 import os |
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4 import time |
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5 |
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6 from . import (LockBase, NotLocked, NotMyLock, LockTimeout, |
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7 AlreadyLocked) |
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8 |
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9 |
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10 class SymlinkLockFile(LockBase): |
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11 """Lock access to a file using symlink(2).""" |
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12 |
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13 def __init__(self, path, threaded=True, timeout=None): |
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14 # super(SymlinkLockFile).__init(...) |
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15 LockBase.__init__(self, path, threaded, timeout) |
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16 # split it back! |
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17 self.unique_name = os.path.split(self.unique_name)[1] |
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18 |
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19 def acquire(self, timeout=None): |
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20 # Hopefully unnecessary for symlink. |
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21 # try: |
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22 # open(self.unique_name, "wb").close() |
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23 # except IOError: |
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24 # raise LockFailed("failed to create %s" % self.unique_name) |
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25 timeout = timeout if timeout is not None else self.timeout |
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26 end_time = time.time() |
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27 if timeout is not None and timeout > 0: |
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28 end_time += timeout |
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29 |
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30 while True: |
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31 # Try and create a symbolic link to it. |
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32 try: |
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33 os.symlink(self.unique_name, self.lock_file) |
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34 except OSError: |
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35 # Link creation failed. Maybe we've double-locked? |
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36 if self.i_am_locking(): |
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37 # Linked to out unique name. Proceed. |
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38 return |
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39 else: |
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40 # Otherwise the lock creation failed. |
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41 if timeout is not None and time.time() > end_time: |
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42 if timeout > 0: |
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43 raise LockTimeout("Timeout waiting to acquire" |
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44 " lock for %s" % |
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45 self.path) |
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46 else: |
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47 raise AlreadyLocked("%s is already locked" % |
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48 self.path) |
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49 time.sleep(timeout / 10 if timeout is not None else 0.1) |
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50 else: |
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51 # Link creation succeeded. We're good to go. |
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52 return |
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53 |
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54 def release(self): |
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55 if not self.is_locked(): |
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56 raise NotLocked("%s is not locked" % self.path) |
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57 elif not self.i_am_locking(): |
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58 raise NotMyLock("%s is locked, but not by me" % self.path) |
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59 os.unlink(self.lock_file) |
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60 |
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61 def is_locked(self): |
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62 return os.path.islink(self.lock_file) |
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63 |
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64 def i_am_locking(self): |
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65 return (os.path.islink(self.lock_file) |
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66 and os.readlink(self.lock_file) == self.unique_name) |
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67 |
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68 def break_lock(self): |
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69 if os.path.islink(self.lock_file): # exists && link |
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70 os.unlink(self.lock_file) |