code: protected void startHeartbeatForThisSession()
    {
      if (enableHeartbeat && !Strings.isNullOrEmpty(masterToken))
      {
        logger.debug("start heartbeat, master token validity: " +
                     masterTokenValidityInSeconds);
  
        HeartbeatBackground.getInstance().addSession(this,
                                                     masterTokenValidityInSeconds, this.heartbeatFrequency);
      }
      else
      {
        logger.debug("heartbeat not enabled for the session");
      }
    }
docs: Start heartbeat for this session