'Initializes the cluster'

@classmethod
def setUpClass(cls):

    try:
        os.unlink('oplog.timestamp')
    except OSError:
        pass
    open('oplog.timestamp', 'w').close()
    cls.repl_set = ReplicaSetSingle().start()
    cls.conn = cls.repl_set.client()
    cls.connector = Connector(mongo_address=cls.repl_set.uri, ns_set=['test.test'], **connector_opts)
    cls.synchronizer = cls.connector.doc_managers[0]
    cls.connector.start()
    assert_soon((lambda : (len(cls.connector.shard_set) != 0)))
