code: @Override
    public void handleSuccessfulDispatch(long clientId, long sentTime) {
      ClientData clientData = core.getClientData(clientId);
      if (sentTime == -1 || clientData == null)
        return;
      
      clientData.markedAsFailedTime = -1;
      if (clientData.markedAsFailedTime != -1) {
        LOG.info("Unmarking " + clientId + " at " + sentTime);
      }
      
      clientData.lastSentTime = sentTime;
    }
docs: Called each time a handleNotification or heartbeat Thrift
  call is successful.
  @param clientId the id of the client on which the call was successful.
  @param sentTime the time at which the call was made. Nothing
  happens if this is -1.