code: @Override
    public void heartbeat() {
      MetaCommand command = null;
      try {
        if (mMasterId.get() == UNINITIALIZED_MASTER_ID) {
          setIdAndRegister();
        }
        command = mMasterClient.heartbeat(mMasterId.get());
        handleCommand(command);
      } catch (IOException e) {
        // An error occurred, log and ignore it or error if heartbeat timeout is reached
        if (command == null) {
          LOG.error("Failed to receive leader master heartbeat command.", e);
        } else {
          LOG.error("Failed to execute leader master heartbeat command: {}", command, e);
        }
        mMasterClient.disconnect();
      }
    }
docs: Heartbeats to the leader master node.