code: public synchronized boolean onRecoverEvaluator(final String evaluatorId) {
      if (getStateOfPreviousEvaluator(evaluatorId).isFailedOrNotExpected()) {
        final String errMsg = "Evaluator with evaluator ID " + evaluatorId + " not expected to be alive.";
        LOG.log(Level.SEVERE, errMsg);
        throw new DriverFatalRuntimeException(errMsg);
      }
  
      if (getStateOfPreviousEvaluator(evaluatorId) != EvaluatorRestartState.EXPECTED) {
        LOG.log(Level.WARNING, "Evaluator with evaluator ID " + evaluatorId + " added to the set" +
            " of recovered evaluators more than once. Ignoring second add...");
        return false;
      }
  
      // set the status for this evaluator ID to be reported.
      setEvaluatorReported(evaluatorId);
  
      if (haveAllExpectedEvaluatorsReported()) {
        onDriverRestartCompleted(false);
      }
  
      return true;
    }
docs: Indicate that this Driver has re-established the connection with one more Evaluator of a previous run.
  @return true if the evaluator has been newly recovered.