[jira] [Created] (SAMZA-542) CheckpointTool NPE's when a partition is empty

["Chris Riccomini (JIRA)" <ji...@apache.org>]

Chris Riccomini created SAMZA-542:
-------------------------------------

             Summary: CheckpointTool NPE's when a partition is empty
                 Key: SAMZA-542
                 URL: https://issues.apache.org/jira/browse/SAMZA-542
             Project: Samza
          Issue Type: Bug
          Components: kafka
    Affects Versions: 0.7.0, 0.8.0
            Reporter: Chris Riccomini
             Fix For: 0.9.0


In the old-style 0.7.0 checkpoint topics, if there is an empty checkpoint partition, the checkpoint tool will NPE with:

{noformat}
Exception in thread "main" java.lang.NullPointerException
	at org.apache.samza.checkpoint.CheckpointTool$$anonfun$readLastCheckpoint$1.apply(CheckpointTool.scala:138)
	at org.apache.samza.checkpoint.CheckpointTool$$anonfun$readLastCheckpoint$1.apply(CheckpointTool.scala:136)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:251)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:251)
	at scala.collection.immutable.HashSet$HashSet1.foreach(HashSet.scala:153)
	at scala.collection.immutable.HashSet$HashTrieSet.foreach(HashSet.scala:306)
	at scala.collection.immutable.HashSet$HashTrieSet.foreach(HashSet.scala:306)
	at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:251)
	at scala.collection.AbstractTraversable.flatMap(Traversable.scala:105)
	at org.apache.samza.checkpoint.CheckpointTool.readLastCheckpoint(CheckpointTool.scala:136)
	at org.apache.samza.checkpoint.CheckpointTool.run(CheckpointTool.scala:122)
	at org.apache.samza.checkpoint.CheckpointTool$.main(CheckpointTool.scala:102)
	at org.apache.samza.checkpoint.CheckpointTool.main(CheckpointTool.scala)
{noformat}

We should verify that this doesn't happen in 0.9.0.

The correct behavior when a checkpoint topic has an empty partition is a little undefined. If the empty partition is expected, this should be ignored. If it's not expected, then an exception should be thrown, or an error printed, or something.

I don't think it's worth back-porting patches for this, but it does warrant a tracker ticket, and verification that it doesn't happen on {{master}}.



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