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Viewing changes to loggerhead/lockfile.py

  • Committer: Robey Pointer
  • Date: 2007-01-02 07:35:34 UTC
  • Revision ID: robey@lag.net-20070102073534-u7tkc8q07xsz9wlv
fewer todos

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loggerhead/lockfile.py
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with_lock = util.with_lock('_tlock', 'LockFile')
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MAX_STALE_TIME = 5 * 60
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class LockFile (object):
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    """
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    lock may be acquired multiple times by the same thread, as long as it's
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    released an equal number of times.  unlike threading.Lock, this lock can
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    be used across processes.
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    this uses os.open(O_CREAT|O_EXCL), which apparently works even on windows,
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    but will not work over NFS, if anyone still uses that.  so don't put the
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    cache folder on an NFS server...
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        # thread lock to maintain internal consistency
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        self._tlock = threading.Lock()
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        self._count = 0
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        if os.path.exists(filename):
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            # remove stale locks left over from a previous run
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            if time.time() - os.stat(filename).st_mtime > MAX_STALE_TIME:
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                os.remove(filename)
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    @with_lock
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    def _try_acquire(self):
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        if self._count > 0:
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            return True
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        except OSError:
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            return False
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    def acquire(self):
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        # try over and over, sleeping on exponential backoff with an upper limit of about 5 seconds
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        pause = 0.1