[SAMZA-1878] NPE when RocksDB restores from changelog topic

• Type: Bug
• Status: Open
• Priority: Blocker
• Resolution: Unresolved
• Affects Version/s: 0.10.1
• Component/s: kv-store

Environment

`samza-kafka_2.10:0.10.1`

`samza-yarn_2.10:0.10.1`

`samza-kv-rocksdb_2.10:0.10.1`

`kafka-clients:0.8.2.2`

kafka cluster version: 1.1.10, the changelog topic turns on log compaction

• Assignee: Unassigned
• Reporter: Frank Hu
• Created: 13/Sep/18 02:44
• Updated: 14/Jan/19 23:19

Description

The job failed to start due to NPE when restoring RocksDB from one Kafka changelog topic. I mark it as a Blocker as it blocks the confidence to use a Kafka changelog as the restoration source for state management

From the log, `keyBytes` is NULL when reading envelope from the changelog topic https://github.com/apache/samza/blob/master/samza-kv/src/main/scala/org/apache/samza/storage/kv/KeyValueStorageEngine.scala#L127

Even though the fix can be as easy as adding a null check, the root cause of null keyBytes may worths a deeper investigation as RocksDB put doesn't allow NULL key and Kafka topic log compaction only set value to NULL.

 

I test using a kafka-consumer to read from the topic directly. However no NULL key messages r found.

 

Detail logs:

INFO o.a.s.s.kv.KeyValueStorageEngine - 1000000 entries restored...
INFO o.a.s.s.kv.KeyValueStorageEngine - 2000000 entries restored...
INFO o.a.s.s.kv.KeyValueStorageEngine - 3000000 entries restored...
java.lang.NullPointerException: null
at scala.collection.mutable.ArrayOps$ofByte$.length$extension(ArrayOps.scala:126)
at scala.collection.mutable.ArrayOps$ofByte.length(ArrayOps.scala:126)
at scala.collection.SeqLike$class.size(SeqLike.scala:106)
at scala.collection.mutable.ArrayOps$ofByte.size(ArrayOps.scala:120)
at org.apache.samza.storage.kv.KeyValueStorageEngine$$anonfun$restore$1.apply(KeyValueStorageEngine.scala:105)
at org.apache.samza.storage.kv.KeyValueStorageEngine$$anonfun$restore$1.apply(KeyValueStorageEngine.scala:90)
at scala.collection.Iterator$class.foreach(Iterator.scala:727)
at scala.collection.AbstractIterator.foreach(Iterator.scala:1157)
at org.apache.samza.storage.kv.KeyValueStorageEngine.restore(KeyValueStorageEngine.scala:90)
at org.apache.samza.storage.TaskStorageManager$$anonfun$restoreStores$3.apply(TaskStorageManager.scala:187)
at org.apache.samza.storage.TaskStorageManager$$anonfun$restoreStores$3.apply(TaskStorageManager.scala:181)
at scala.collection.TraversableLike$WithFilter$$anonfun$foreach$1.apply(TraversableLike.scala:772)
at scala.collection.immutable.Map$Map1.foreach(Map.scala:109)
at scala.collection.TraversableLike$WithFilter.foreach(TraversableLike.scala:771)
at org.apache.samza.storage.TaskStorageManager.restoreStores(TaskStorageManager.scala:181)
at org.apache.samza.storage.TaskStorageManager.init(TaskStorageManager.scala:76)
at org.apache.samza.container.TaskInstance.startStores(TaskInstance.scala:99)
at org.apache.samza.container.SamzaContainer$$anonfun$startStores$2.apply(SamzaContainer.scala:677)
at org.apache.samza.container.SamzaContainer$$anonfun$startStores$2.apply(SamzaContainer.scala:675)
at scala.collection.Iterator$class.foreach(Iterator.scala:727)
at scala.collection.AbstractIterator.foreach(Iterator.scala:1157)
at scala.collection.MapLike$DefaultValuesIterable.foreach(MapLike.scala:206)
at org.apache.samza.container.SamzaContainer.startStores(SamzaContainer.scala:675)
at org.apache.samza.container.SamzaContainer.run(SamzaContainer.scala:586)
at org.apache.samza.container.SamzaContainer$.safeMain(SamzaContainer.scala:82)
at org.apache.samza.container.SamzaContainer$.main(SamzaContainer.scala:56)
at org.apache.samza.container.SamzaContainer.main(SamzaContainer.scala)