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- from __future__ import absolute_import
-
- import os
- import time
-
- from . import (LockBase, NotLocked, NotMyLock, LockTimeout,
- AlreadyLocked)
-
-
- class SymlinkLockFile(LockBase):
- """Lock access to a file using symlink(2)."""
-
- def __init__(self, path, threaded=True, timeout=None):
- # super(SymlinkLockFile).__init(...)
- LockBase.__init__(self, path, threaded, timeout)
- # split it back!
- self.unique_name = os.path.split(self.unique_name)[1]
-
- def acquire(self, timeout=None):
- # Hopefully unnecessary for symlink.
- # try:
- # open(self.unique_name, "wb").close()
- # except IOError:
- # raise LockFailed("failed to create %s" % self.unique_name)
- timeout = timeout if timeout is not None else self.timeout
- end_time = time.time()
- if timeout is not None and timeout > 0:
- end_time += timeout
-
- while True:
- # Try and create a symbolic link to it.
- try:
- os.symlink(self.unique_name, self.lock_file)
- except OSError:
- # Link creation failed. Maybe we've double-locked?
- if self.i_am_locking():
- # Linked to out unique name. Proceed.
- return
- else:
- # Otherwise the lock creation failed.
- if timeout is not None and time.time() > end_time:
- if timeout > 0:
- raise LockTimeout("Timeout waiting to acquire"
- " lock for %s" %
- self.path)
- else:
- raise AlreadyLocked("%s is already locked" %
- self.path)
- time.sleep(timeout / 10 if timeout is not None else 0.1)
- else:
- # Link creation succeeded. We're good to go.
- return
-
- def release(self):
- if not self.is_locked():
- raise NotLocked("%s is not locked" % self.path)
- elif not self.i_am_locking():
- raise NotMyLock("%s is locked, but not by me" % self.path)
- os.unlink(self.lock_file)
-
- def is_locked(self):
- return os.path.islink(self.lock_file)
-
- def i_am_locking(self):
- return (os.path.islink(self.lock_file)
- and os.readlink(self.lock_file) == self.unique_name)
-
- def break_lock(self):
- if os.path.islink(self.lock_file): # exists && link
- os.unlink(self.lock_file)
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