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### What changes were proposed in this pull request? Close LevelDBIterator when LevelDB.close() is called. ### Why are the changes needed? This pull request would prevent JNI resources leaking from Level DB instance and its' iterators. In before implementation JNI resources from LevelDBIterator are cleaned by finalize() function. This behavior is also mentioned in comments of ["LevelDBIterator.java"](https://github.com/apache/spark/blob/master/common/kvstore/src/main/java/org/apache/spark/util/kvstore/LevelDBIterator.java) by squito . But if DB instance is already closed, then iterator's close method would be ignored. LevelDB's iterator would keep level db files opened (for the case table cache is filled up), till iterator.close() is called. Then these JNI resources (file handle) would be leaked. This JNI resource leaking issue would cause the problem described in [SPARK-31929](https://issues.apache.org/jira/browse/SPARK-31929) on Windows: in spark history server, leaked file handle for level db files would trigger "IOException" when HistoryServerDiskManager try to remove them for releasing disk space.  ### Does this PR introduce _any_ user-facing change? No ### How was this patch tested? Add unit test and manually tested it. Closes #28769 from zhli1142015/close-leveldbiterator-when-leveldb.close. Authored-by: Zhen Li <zhli@microsoft.com> Signed-off-by: Sean Owen <srowen@gmail.com> |
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