@Override
        public BoxedUnit apply(Exception exception, ExponentialSleepStrategy.RetryLoop loop) {
          if (loop.sleepCount() < MAX_RETRIES_ON_EXCEPTION) {
            LOG.warn(
                String.format("Fetching SSP metadata for: %s threw an exception. Retrying.", ssps), exception);
          } else {
            LOG.error(String.format("Fetching SSP metadata for: %s threw an exception.", ssps), exception);
            loop.done();
            throw new SamzaException(exception);
          }
          return null;
        }
Given a set of SystemStreamPartition, fetch metadata from Kafka for each
of them, and return a map from ssp to SystemStreamPartitionMetadata for
each of them. This method will return null for oldest and newest offsets
if a given SystemStreamPartition is empty. This method will block and
retry indefinitely until it gets a successful response from Kafka.
@param ssps a set of strings of SSP
@param retryBackoff retry backoff strategy
@return a map from ssp to sspMetadata which has offsets
samza-kafka/src/main/java/org/apache/samza/system/kafka/KafkaSystemAdmin.java