memcache_adapter.py 文件源码

def _cache(self, key, data):
        current_lock = self._lock_value()
        with self.client_pool.reserve() as client:
            while True:
                value, cid = client.gets(key)
                # If there is a lock value in Memcache that is
                # different from our own we have to bail.
                if value and value.startswith(self._lock_prefix) and value != current_lock:
                    return

                # If there isn't a value at all, we have to add one
                # and try again.
                if cid is None:
                    client.add(key, current_lock, self._lock_timeout)
                    continue

                try:
                    return client.cas(key, data, cid, self._item_timeout)

                # There is a small chance that between the `gets` and
                # "now" the key will have been deleted by a concurrent
                # process, so we account for that possibility here.
                except pylibmc.NotFound:  # pragma: no cover
                    return