[jira] Commented: (HBASE-3583) Coprocessors: RegionObserver: ScannerNext and ScannerClose hooks are called when get() is invoked

["Andrew Purtell (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-3583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13001096#comment-13001096 ] 

Andrew Purtell commented on HBASE-3583:
---------------------------------------

We discussed this internally. Reasonable options are:

1) Rework the Coprocessor RegionObserver API so "everything is a scan"

2) Pass booleans to internal functions to distinguish between the code paths

We are opting for #2. A feature of the RegionObserver API is it mirrors HRegionInterface so the user/implementor has precise options for overriding or augmenting client actions. 

> Coprocessors: RegionObserver: ScannerNext and ScannerClose hooks are called when get() is invoked
> -------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-3583
>                 URL: https://issues.apache.org/jira/browse/HBASE-3583
>             Project: HBase
>          Issue Type: Bug
>          Components: coprocessors
>    Affects Versions: 0.92.0
>            Reporter: Mingjie Lai
>            Assignee: Mingjie Lai
>             Fix For: 0.92.0
>
>
> RegionObserver upcalls are expected to be triggered by corresponding client calls. 
> I found that if a HTable.get() is issued, ScannerNext, and ScannerClose hooks are also invoked. 
> Here is the reason: HRegion.get() is implemented with an internal scanner:
> {code}
>     InternalScanner scanner = null;
>     try {
>       scanner = getScanner(scan);
>       scanner.next(results);
>     } finally {
>       if (scanner != null)
>         scanner.close();
>     }
> {code}
> where scanner.next, and scanner.close() are implemented with RegionObserver hooks. 

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