def heartbeat(self):
        pipeline = self.conn.pipeline()
        now = time.time()
        for replica in self.replicas:
            pipeline.zadd(self.key, '{start}:{name}'.format(
                start=replica[0],
                name=replica[1]
            ), now)
        ret = pipeline.execute()

        # Only notify the other nodes if we're not in the ring yet.
        if any(ret):
            self._notify()
Add/update the node in Redis. Needs to be called regularly by the
dataset/ETHPy150Open closeio/redis-hashring/redis_hashring/__init__.py/RingNode.heartbeat