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https://issues.apache.org/jira/browse/HBASE-10656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15587191#comment-15587191
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stack commented on HBASE-10656:
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[~mi...@cloudera.com] There was no load on the cluster, right?
> high-scale-lib's Counter depends on Oracle (Sun) JRE, and also has some bug
> ----------------------------------------------------------------------------
>
> Key: HBASE-10656
> URL: https://issues.apache.org/jira/browse/HBASE-10656
> Project: HBase
> Issue Type: Bug
> Reporter: Hiroshi Ikeda
> Assignee: Hiroshi Ikeda
> Priority: Minor
> Fix For: 0.96.2, 0.98.1, 0.99.0
>
> Attachments: 10656-098.v2.txt, 10656-trunk.v2.patch, 10656.096v2.txt,
> HBASE-10656-0.96.patch, HBASE-10656-addition.patch, HBASE-10656-trunk.patch,
> MyCounter.java, MyCounter2.java, MyCounter3.java, MyCounterTest.java,
> MyCounterTest.java, PerformanceTestApp.java, PerformanceTestApp2.java,
> output.pdf, output.txt, output2.pdf, output2.txt
>
>
> Cliff's high-scale-lib's Counter is used in important classes (for example,
> HRegion) in HBase, but Counter uses sun.misc.Unsafe, that is implementation
> detail of the Java standard library and belongs to Oracle (Sun). That
> consequently makes HBase depend on the specific JRE Implementation.
> To make matters worse, Counter has a bug and you may get wrong result if you
> mix a reading method into your logic calling writing methods.
> In more detail, I think the bug is caused by reading an internal array field
> without resolving memory caching, which is intentional the comment says, but
> storing the read result into a volatile field. That field may be not changed
> after you can see the true values of the array field, and also may be not
> changed after updating the "next" CAT instance's values in some race
> condition when extending CAT instance chain.
> Anyway, it is possible that you create a new alternative class which only
> depends on the standard library. I know Java8 provides its alternative, but
> HBase should support Java6 and Java7 for some time.
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