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from uhashring import HashRing
__all__ = ["patch_memcache"]
def patch_memcache():
"""Monkey patch python-memcached to implement our consistent hashring
in its node selection and operations.
"""
def _init(self, servers, *k, **kw):
self._old_init(servers, *k, **kw)
nodes = {}
for server in self.servers:
conf = {
"hostname": server.ip,
"instance": server,
"port": server.port,
"weight": server.weight,
}
nodes[server.ip] = conf
self.uhashring = HashRing(nodes)
def _get_server(self, key):
if isinstance(key, tuple):
return self._old_get_server(key)
for i in range(self._SERVER_RETRIES):
for node in self.uhashring.range(key):
if node["instance"].connect():
return node["instance"], key
return None, None
memcache = __import__("memcache")
memcache.Client._old_get_server = memcache.Client._get_server
memcache.Client._old_init = memcache.Client.__init__
memcache.Client.__init__ = _init
memcache.Client._get_server = _get_server
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