Mercurial > kallithea
view rhodecode/lib/vcs/utils/lockfiles.py @ 3774:60335b702a00 beta
invalidation: don't create CacheInvalidation records on startup
Creating the records early gave an advantage before lightweight was introduced.
With lightweight it is no longer necessary.
The records will be created on demand anyway and there is no reason to create and
maintain them before they are used.
author | Mads Kiilerich <madski@unity3d.com> |
---|---|
date | Wed, 03 Apr 2013 15:56:12 +0200 |
parents | 95a226b35b91 |
children |
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import os class LockFile(object): """Provides methods to obtain, check for, and release a file based lock which should be used to handle concurrent access to the same file. As we are a utility class to be derived from, we only use protected methods. Locks will automatically be released on destruction""" __slots__ = ("_file_path", "_owns_lock") def __init__(self, file_path): self._file_path = file_path self._owns_lock = False def __del__(self): self._release_lock() def _lock_file_path(self): """:return: Path to lockfile""" return "%s.lock" % (self._file_path) def _has_lock(self): """:return: True if we have a lock and if the lockfile still exists :raise AssertionError: if our lock-file does not exist""" if not self._owns_lock: return False return True def _obtain_lock_or_raise(self): """Create a lock file as flag for other instances, mark our instance as lock-holder :raise IOError: if a lock was already present or a lock file could not be written""" if self._has_lock(): return lock_file = self._lock_file_path() if os.path.isfile(lock_file): raise IOError("Lock for file %r did already exist, delete %r in case the lock is illegal" % (self._file_path, lock_file)) try: fd = os.open(lock_file, os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0) os.close(fd) except OSError,e: raise IOError(str(e)) self._owns_lock = True def _obtain_lock(self): """The default implementation will raise if a lock cannot be obtained. Subclasses may override this method to provide a different implementation""" return self._obtain_lock_or_raise() def _release_lock(self): """Release our lock if we have one""" if not self._has_lock(): return # if someone removed our file beforhand, lets just flag this issue # instead of failing, to make it more usable. lfp = self._lock_file_path() try: # on bloody windows, the file needs write permissions to be removable. # Why ... if os.name == 'nt': os.chmod(lfp, 0777) # END handle win32 os.remove(lfp) except OSError: pass self._owns_lock = False