public String getNewestOffset() {
      return newestOffset;
    }
@return The newest offset that exists in the stream for the partition
        given. If a partition has two messages with offsets 0 and 1,
        respectively, then this method would return 1 for the newest
        offset. This offset is useful when one wishes to see if all
        messages have been read from a stream (offset of last message
        read == newest offset). A null value means the stream is empty.
samza-api/src/main/java/org/apache/samza/system/SystemStreamMetadata.java