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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10656) high-scale-lib's Counter depends on Oracle (Sun) JRE, and also has some bug
Date Tue, 04 Mar 2014 04:29:21 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13919004#comment-13919004
] 

stack commented on HBASE-10656:
-------------------------------

bq. On the contrary, high-scale-lib crachs in runtime when it fails to find Unsafe.

We should have a fallback implementation as you suggest.

>  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
>            Priority: Minor
>         Attachments: MyCounter.java, MyCounterTest.java
>
>
> 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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