code: private boolean isJobSuccessful(String objectKey) {
      LOG.trace("isJobSuccessful: for {}", objectKey);
      if (mCachedSparkJobsStatus.containsKey(objectKey)) {
        LOG.trace("isJobSuccessful: {} found cached", objectKey);
        return mCachedSparkJobsStatus.get(objectKey).booleanValue();
      }
      String key = getRealKey(objectKey);
      Path p = new Path(key, HADOOP_SUCCESS);
      ObjectMetadata statusMetadata = getObjectMetadata(p.toString());
      Boolean isJobOK = Boolean.FALSE;
      if (statusMetadata != null) {
        isJobOK = Boolean.TRUE;
      }
      LOG.debug("isJobSuccessful: not cached {}. Status is {}", objectKey, isJobOK);
      mCachedSparkJobsStatus.put(objectKey, isJobOK);
      return isJobOK.booleanValue();
    }
docs: Checks if container/object contains container/object/_SUCCESS If so, this
  object was created by successful Hadoop job
  
  @param objectKey
  @return boolean if job is successful