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https://issues.apache.org/jira/browse/KAFKA-1721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14178856#comment-14178856
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Bhavesh Mistry commented on KAFKA-1721:
---------------------------------------
I have filled https://github.com/xerial/snappy-java/issues/88 for tracking for
Snappy.
There is patch provided and Thanks to [~ewencp] for testing the patch. Please
see above link for more details.
Thanks,
Bhavesh
> Snappy compressor is not thread safe
> ------------------------------------
>
> Key: KAFKA-1721
> URL: https://issues.apache.org/jira/browse/KAFKA-1721
> Project: Kafka
> Issue Type: Bug
> Components: compression
> Reporter: Ewen Cheslack-Postava
> Assignee: Ewen Cheslack-Postava
>
> From the mailing list, it can generate this exception:
> 2014-10-20 18:55:21.841 [kafka-producer-network-thread] ERROR
> org.apache.kafka.clients.producer.internals.Sender - Uncaught error in
> kafka producer I/O thread:
> *java.lang.NullPointerException*
> at
> org.xerial.snappy.BufferRecycler.releaseInputBuffer(BufferRecycler.java:153)
> at org.xerial.snappy.SnappyOutputStream.close(SnappyOutputStream.java:317)
> at java.io.FilterOutputStream.close(FilterOutputStream.java:160)
> at org.apache.kafka.common.record.Compressor.close(Compressor.java:94)
> at
> org.apache.kafka.common.record.MemoryRecords.close(MemoryRecords.java:119)
> at
> org.apache.kafka.clients.producer.internals.RecordAccumulator.drain(RecordAccumulator.java:285)
> at org.apache.kafka.clients.producer.internals.Sender.run(Sender.java:162)
> at org.apache.kafka.clients.producer.internals.Sender.run(Sender.java:115)
> at java.lang.Thread.run(Thread.java:744)
> This appears to be an issue with the snappy-java library using ThreadLocal
> for an internal buffer recycling object which results in that object being
> shared unsafely across threads if one thread sends to multiple producers:
> {quote}
> I think the issue is that you're
> using all your producers across a thread pool and the snappy library
> uses ThreadLocal BufferRecyclers. When new Snappy streams are allocated,
> they may be allocated from the same thread (e.g. one of your MyProducer
> classes calls Producer.send() on multiple producers from the same
> thread) and therefore use the same BufferRecycler. Eventually you hit
> the code in the stacktrace, and if two producer send threads hit it
> concurrently they improperly share the unsynchronized BufferRecycler.
> This seems like a pain to fix -- it's really a deficiency of the snappy
> library and as far as I can see there's no external control over
> BufferRecycler in their API. One possibility is to record the thread ID
> when we generate a new stream in Compressor and use that to synchronize
> access to ensure no concurrent BufferRecycler access. That could be made
> specific to snappy so it wouldn't impact other codecs. Not exactly
> ideal, but it would work. Unfortunately I can't think of any way for you
> to protect against this in your own code since the problem arises in the
> producer send thread, which your code should never know about.
> Another option would be to setup your producers differently to avoid the
> possibility of unsynchronized access from multiple threads (i.e. don't
> use the same thread pool approach), but whether you can do that will
> depend on your use case.
> {quote}
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