private Set<SystemStreamPartition> getWorkingSSPSet(RunLoopTask task) {

      Set<SystemStreamPartition> allPartitions = task.systemStreamPartitions();

      // filter only those SSPs that are not at end of stream.
      Set<SystemStreamPartition> workingSSPSet = allPartitions.stream()
          .filter(ssp -> !consumerMultiplexer.isEndOfStream(ssp))
          .collect(Collectors.toSet());
      return workingSSPSet;
    }
Returns those partitions for the task for which we have not received end-of-stream from the consumer.
@param task
@return a Set of SSPs such that all SSPs are not at end of stream.
samza-core/src/main/java/org/apache/samza/container/RunLoop.java