[SPARK-7766] KryoSerializerInstance reuse is not safe when auto-reset is disabled

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.4.0
• Fix Version/s: 1.4.0
• Component/s: Spark Core
• Target Version/s: 1.4.0
• Assignee: Josh Rosen
• Reporter: Josh Rosen
• Created: 20/May/15 20:16
• Updated: 26/May/15 17:24
• Resolved: 22/May/15 20:29

Description

SPARK-3386 modified the shuffle write path to re-use serializer instances across multiple calls to DiskBlockObjectWriter. It turns out that this introduced a very rare bug when using KryoSerializer: if auto-reset is disabled and reference-tracking is enabled, then we'll end up re-using the same serializer instance to write multiple output streams without calling reset() between write calls, which can lead to cases where objects in one file may contain references to objects that are in previous files, which can cause errors during deserialization.

The fix should be simple: add reset calls at the end of serialize and serializeStream.

Thanks to John Carrino for reporting this issue on GItHub: https://github.com/apache/spark/pull/5606#issuecomment-103995103

Issue Links

• is broken by: SPARK-3386 Reuse serializer and serializer buffer in shuffle block iterator
• links to: [Github] Pull Request #6293 (JoshRosen)