|
|
- from __future__ import absolute_import
-
- import time
- import os
-
- from . import (LockBase, LockFailed, NotLocked, NotMyLock, LockTimeout,
- AlreadyLocked)
-
-
- class LinkLockFile(LockBase):
- """Lock access to a file using atomic property of link(2).
-
- >>> lock = LinkLockFile('somefile')
- >>> lock = LinkLockFile('somefile', threaded=False)
- """
-
- def acquire(self, timeout=None):
- 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 hard link to it.
- try:
- os.link(self.unique_name, self.lock_file)
- except OSError:
- # Link creation failed. Maybe we've double-locked?
- nlinks = os.stat(self.unique_name).st_nlink
- if nlinks == 2:
- # The original link plus the one I created == 2. We're
- # good to go.
- return
- else:
- # Otherwise the lock creation failed.
- if timeout is not None and time.time() > end_time:
- os.unlink(self.unique_name)
- 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 is not None and timeout / 10 or 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 os.path.exists(self.unique_name):
- raise NotMyLock("%s is locked, but not by me" % self.path)
- os.unlink(self.unique_name)
- os.unlink(self.lock_file)
-
- def is_locked(self):
- return os.path.exists(self.lock_file)
-
- def i_am_locking(self):
- return (self.is_locked() and
- os.path.exists(self.unique_name) and
- os.stat(self.unique_name).st_nlink == 2)
-
- def break_lock(self):
- if os.path.exists(self.lock_file):
- os.unlink(self.lock_file)
|
