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https://issues.apache.org/jira/browse/SAMZA-966?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jake Maes updated SAMZA-966:
----------------------------
Labels: newbie++ (was: )
> Performance: Remove finalizer from RocksDbIterator
> --------------------------------------------------
>
> Key: SAMZA-966
> URL: https://issues.apache.org/jira/browse/SAMZA-966
> Project: Samza
> Issue Type: Bug
> Reporter: Jake Maes
> Labels: newbie++
>
> It is well-known that finalizable objects hurt GC performance. Josh Bloch
> covers it in Effective Java.
> We have one finalizer in Samza for RocksDbIterator. This is bad because:
> 1. RocksDbIterators can be created and destroyed very frequently and making
> them disposable makes it harder for the nursery to clean them up.
> 2. It's not necessary. Finalize calls close() which calls dispose() on
> RocksObject. The javaDoc for that method is pretty clear:
> {quote}
> /**
> * Release the c++ object manually pointed by the native handle.
> * <p>
> * Note that {@code dispose()} will also be called during the GC process
> * if it was not called before its {@code RocksObject} went out-of-scope.
> * However, since Java may wrongly wrongly assume those objects are
> * small in that they seems to only hold a long variable. As a result,
> * they might have low priority in the GC process. To prevent this,
> * it is suggested to call {@code dispose()} manually.
> * </p>
> * <p>
> * Note that once an instance of {@code RocksObject} has been disposed,
> * calling its function will lead undefined behavior.
> * </p>
> */
> {quote}
> Sounds like the memory will eventually be freed. So we're paying a tax just
> to play big brother.
> Instead, I think we should document that KeyValueIterator should be always be
> closed, remove the finalizer from RocksDbIterator, and update
> KeyValueIterator to also extend Closeable, which will enable the
> try-with-resources pattern
> https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html
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