`Smile` decoding issue with `NonBlockingByteArrayParser`, concurrency about jackson-dataformats-binary HOT 4 CLOSED

Thanks for the information !
It seems, indeed, to be a problematic similar to #479

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Thank you for reporting this, @simondaudin -- and especially for providing the reproduction!

Without looking too deep, based on failure and test code, it does seem like a legit bug somewhere and not incorrect usage.
But I hope to add more information when I have time to look into this problem.

from jackson-dataformats-binary.

Hello, thanks for the response.

I actually got curious and went digging a little bit.
It seems due to SmileBufferRecycler being created in the main thread and so, created only once in SmileParserBase ThreadLocal _smileRecyclerRef and then used inside all the parallel thread.
Second problem, in SmileBufferRecycler there is a race condition between the get and the set to null.

I tried two solutions that both worked:

• wrapped SmileBufferRecycler._seenNamesBuffer in an AtomicReference
• replacing the SmileParserBase._smileBufferRecycler field by the method with the same name so that it is lazily instantiated by the correct thread when needed

In the first solution, we only have one instance of SmileBufferRecycler shared by all the parallel threads.
I had no further insights about what it was supposed to be in this context, so I was not sure about making a PR.

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This may be due to earlier assumptions that parser instances were bound 1-to-1 on threads, and as such buffer recyclers would work without explicit synchronization as long as ThreadLocal was used. This turned out not to be the case with async processing, and changes have been made in jackson-core for recycling of symbol tables, for example.

But I suspect not for SmileBufferRecycler; it predates async Smile parser as well.

So this gives a reasonable idea that adding unfortunate-but-now-necessary locking is probably needed.
src/main/java/com/fasterxml/jackson/core/util/BufferRecycler.java from jackson-core may provide some clues, I forget exact changes that have been made over various versions.

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