[jira] [Created] (TEZ-3776) ShuffleHandler can theoretically NPE if all partitions in the ranged fetch are empty

[Kuhu Shukla (JIRA)]

Kuhu Shukla created TEZ-3776:
--------------------------------

             Summary: ShuffleHandler can theoretically NPE if all partitions in 
the ranged fetch are empty
                 Key: TEZ-3776
                 URL: https://issues.apache.org/jira/browse/TEZ-3776
             Project: Apache Tez
          Issue Type: Bug
            Reporter: Kuhu Shukla


{code}
if (index.getPartLength() != 0) {
          if (firstIndex == null) {
            firstIndex = index;
          }
          lastIndex = index;
        }

        ShuffleHeader header = new ShuffleHeader(mapId, index.getPartLength(), 
index.getRawLength(), reduce);
        DataOutputBuffer dob = new DataOutputBuffer();
        header.write(dob);
        ch.write(wrappedBuffer(dob.getData(), 0, dob.getLength()));
      }

      final long rangeOffset = firstIndex.getStartOffset(); <<<<<<<<<<<<<<<<<
{code}
In cases where tez.runtime.empty.partitions.info-via-events.enabled is false 
and is respected (say post TEZ-3287, if not handled correctly at the output 
side, the shuffle handler assumes that if it has got to this point there is at 
least one non empty partition. The ShuffleHandler should protect itself from 
this NPE.



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