Thread Safety and Memory Leaks in HCatRecordObjectInspectorFactory

Summary

There are a couple of issues in HCatRecordObjectInspectorFactory[1] because it uses a static Java HashMap to cache objects:

1. Java HashMap is not thread safe. This can lead to data corruptions and race conditions in multithreaded servers when two threads update the ObjectInspector.
2. There is no eviction policy and as a result, this can result in memory leaks. If user reads a lot of different schemas, Hive server will start seeing memory pressure, once it start going to have a lot of cached record and object inspectors.

This patch propose to replace the cache using a Guava cache which enables cache evictions and thread safety. Guava cache is already used in Hive ObjectInspectorFactory [2], so this change is consistent with the rest of Hive.

Attached is a patch that fixes this issue.

References:

1. https://github.com/apache/hive/blob/b58d50cb73a1f79a5d079e0a2c5ac33d2efc33a0/hcatalog/core/src/main/java/org/apache/hive/hcatalog/data/HCatRecordObjectInspectorFactory.java#L44-L47
2. https://github.com/apache/hive/blob/b58d50cb73a1f79a5d079e0a2c5ac33d2efc33a0/serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/ObjectInspectorFactory.java#L68-L87

Review Board Link:

•  https://reviews.apache.org/r/70674/