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https://issues.apache.org/jira/browse/HBASE-16626?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15488180#comment-15488180
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Yu Li commented on HBASE-16626:
-------------------------------

For branch-1 it's a little bit awkward, since for jdk7 or lower we have to 
change RegionScanner to abstract class to add a default behavior, which also 
requires customer code to change (implements RegionScanner -> extends 
RegionScanner)... So we decided to change the customer coprocessor code 
directly (and luckily our customer accept this way)...

Just to make it clear to others, for branch-1 the problem only exists after we 
did a backport of the read-path offheap work, no need to worry if using 
official released versions. :-)

> User customized RegionScanner from 1.X is incompatible with 2.0.0's off-heap 
> part
> ---------------------------------------------------------------------------------
>
>                 Key: HBASE-16626
>                 URL: https://issues.apache.org/jira/browse/HBASE-16626
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Offheaping
>    Affects Versions: 1.2.2, 1.1.6
>            Reporter: Charlie Qiangeng Xu
>             Fix For: 2.0.0
>
>
> Introduced by 2.0.0's off-heap feature, the interface RegionScanner extends a 
> new interface Shipper which contains a  "shipped()" method. 
> In our case, some application user defined customized scanner that implements 
> Interface RegionScanner in 1.X . 
> After we back ported the Off Heap feature of 2.0.0, 
> RegionScannerShippedCallBack throws a "java.lang.AbstractMethodError" when 
> executing scanner.shipped(). It is because the customized scanner didn't 
> override the shipped method yet.
> Instead of forcing every user to add a empty implementation(if they don't 
> really need to scan the file or the RS don't use L2 cache, they don't need to 
> do anything in shipped method) , adding a default method of shipped in 
> Interface  RegionScanner might be a better way.



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