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https://issues.apache.org/jira/browse/PARQUET-2126?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17573826#comment-17573826
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Timothy Miller commented on PARQUET-2126:
-----------------------------------------
Thanks, Steve. I really like your suggestion. I think we should already hold
off on this PR because I'm pretty sure the double-pooling is a problem. So I'll
see about looking into this and maybe implement something completely different.
> Thread safety bug in CodecFactory
> ---------------------------------
>
> Key: PARQUET-2126
> URL: https://issues.apache.org/jira/browse/PARQUET-2126
> Project: Parquet
> Issue Type: Bug
> Components: parquet-mr
> Affects Versions: 1.12.2
> Reporter: James Turton
> Priority: Major
>
> The code for returning Compressor objects to the caller goes to some lengths
> to achieve thread safety, including keeping Codec objects in an Apache
> Commons pool that has thread-safe borrow semantics. This is all undone by
> the BytesCompressor and BytesDecompressor Maps in
> org.apache.parquet.hadoop.CodecFactory which end up caching single compressor
> and decompressor instances due to code in CodecFactory@getCompressor and
> CodecFactory@getDecompressor. When the caller runs multiple threads, those
> threads end up sharing compressor and decompressor instances.
> For compressors based on Xerial Snappy this bug has no effect because that
> library is itself thread safe. But when BuiltInGzipCompressor from Hadoop is
> selected for the CompressionCodecName.GZIP case, serious problems ensue.
> That class is not thread safe and sharing one instance of it between threads
> produces both silent data corruption and JVM crashes.
> To fix this situation, parquet-mr should stop caching single compressor and
> decompressor instances.
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