I think it's basically possible to do locking, mutexes, semaphores, etc in
memcache, by taking advantage of some of the semantics, plus the new-ish
compare & store stuff. There's the obvious caveat that it could be flushed
without warning, or disabled for a while, so it's not a high reliability
thing.
def add(self, key, value, time=0, min_compress_len=0, namespace=None):
"""Sets a key's value, iff item is not already in memcache.
def replace(self, key, value, time=0, min_compress_len=0, namespace=None):
"""Replaces a key's value, failing if item isn't already in memcache.
def cas(self, key, value, time=0, min_compress_len=0, namespace=None):
"""Compare-And-Set update.
def incr(self, key, delta=1, namespace=None, initial_value=None):
"""Atomically increments a key's value.
def decr(self, key, delta=1, namespace=None, initial_value=None):
"""Atomically decrements a key's value.
It seems to me the you could carefully use the above in various creative
ways to implement this, if you require frequent use and the datastore costs
would be prohibitive for it.
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