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https://issues.apache.org/jira/browse/HBASE-22539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16856697#comment-16856697
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Duo Zhang commented on HBASE-22539:
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And in fact, a DBB.get is also an Unsafe.copyMemory, you can see the
implementation in DirectByteBuffer.get, it just calls Bits.copyToArray, which
is almost the same with our ByteBufferUtils.copyFromBufferToArray...
> Potential WAL corruption due to Unsafe.copyMemory usage when DBB are in place
> -----------------------------------------------------------------------------
>
> Key: HBASE-22539
> URL: https://issues.apache.org/jira/browse/HBASE-22539
> Project: HBase
> Issue Type: Bug
> Components: rpc, wal
> Affects Versions: 2.1.1
> Reporter: Wellington Chevreuil
> Priority: Blocker
>
> Summary
> We had been chasing a WAL corruption issue reported on one of our customers
> deployments running release 2.1.1 (CDH 6.1.0). After providing a custom
> modified jar with the extra sanity checks implemented by HBASE-21401 applied
> on some code points, plus additional debugging messages, we believe it is
> related to DirectByteBuffer usage, and Unsafe copy from offheap memory to
> on-heap array triggered
> [here|https://github.com/apache/hbase/blob/branch-2.1/hbase-common/src/main/java/org/apache/hadoop/hbase/util/ByteBufferUtils.java#L1157],
> such as when writing into a non ByteBufferWriter type, as done
> [here|https://github.com/apache/hbase/blob/branch-2.1/hbase-common/src/main/java/org/apache/hadoop/hbase/io/ByteBufferWriterOutputStream.java#L84].
> More details on the following comment.
>
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