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  • Committer: Michael Hudson
  • Date: 2010-05-07 01:03:17 UTC
  • mfrom: (414.1.1 loggerhead)
  • Revision ID: michael.hudson@canonical.com-20100507010317-kr5ipx6qgn65636o
(mkanat) use a global lock to protect access to the lru cache

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loggerhead/history.py
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                filename=rich_filename(paths[1], kind),
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                file_id=file_id))
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# The lru_cache is not thread-safe, so we need a lock around it for
 
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# all threads.
 
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rev_info_memory_cache_lock = threading.RLock()
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class RevInfoMemoryCache(object):
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    """A store that validates values against the revids they were stored with.
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    def __init__(self, cache):
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        self._cache = cache
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        # lru_cache is not thread-safe, so we need to lock all accesses.
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        # It is even modified when doing a get() on it.
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        self._lock = threading.RLock()
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    def get(self, key, revid):
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        """Return the data associated with `key`, subject to a revid check.
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        If a value was stored under `key`, with the same revid, return it.
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        Otherwise return None.
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        """
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        self._lock.acquire()
 
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        rev_info_memory_cache_lock.acquire()
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        try:
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            cached = self._cache.get(key)
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        finally:
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            self._lock.release()
 
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            rev_info_memory_cache_lock.release()
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        if cached is None:
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            return None
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        stored_revid, data = cached
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    def set(self, key, revid, data):
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        """Store `data` under `key`, to be checked against `revid` on get().
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        """
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        self._lock.acquire()
 
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        rev_info_memory_cache_lock.acquire()
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        try:
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            self._cache[key] = (revid, data)
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        finally:
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            self._lock.release()
 
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            rev_info_memory_cache_lock.release()
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# Used to store locks that prevent multiple threads from building a 
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# revision graph for the same branch at the same time, because that can