b5737ee59a
* Refactor heartbeat logic
Currently we only have Backend heartbeat. And without Frontend
or Broker heartbeat, we don't know the status of these nodes,
thus can't do failover logic in some cases.
1. Add Frontend and Broker heartbeat.
Frontend heartbeat using BootstrapFinish http rest api
Broker heartbeat using ping() rpc.
2. All heartbeats are managed in HeartbeatMgr.
3. Rename BrokerAddress to FsBroker.