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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11667) Comment ClientScanner logic for NSREs.
Date Wed, 06 Aug 2014 21:17:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11667?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14088268#comment-14088268
] 

Hudson commented on HBASE-11667:
--------------------------------

FAILURE: Integrated in HBase-TRUNK #5375 (See [https://builds.apache.org/job/HBase-TRUNK/5375/])
HBASE-11667 Comment ClientScanner logic for NSREs. (larsh: rev 25e6baee424602942afbe40b01ea0b4cff1ea9b1)
* hbase-client/src/main/java/org/apache/hadoop/hbase/client/ClientScanner.java


> Comment ClientScanner logic for NSREs.
> --------------------------------------
>
>                 Key: HBASE-11667
>                 URL: https://issues.apache.org/jira/browse/HBASE-11667
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>            Priority: Minor
>             Fix For: 0.99.0, 2.0.0, 0.94.23, 0.98.6
>
>         Attachments: 11667-0.94.txt, 11667-doc-0.94.txt, 11667-trunk.txt, HBASE-11667-0.98.patch,
IntegrationTestBigLinkedListWithRegionMovement.patch
>
>
> We ran into an issue with Phoenix where a RegionObserver coprocessor intercepts a scan
and returns an aggregate (in this case a count) with a fake row key. It turns out this does
not work when the {{ClientScanner}} encounters NSREs, as it uses the last key it saw to reset
the scanner to try again (which in this case would be the fake key).
> While this is arguably a rare case and one could also argue that a region observer just
shouldn't do this... While looking at {{ClientScanner}}'s code I found this logic not necessary.
> A NSRE occurred because we contacted a region server with a key that it no longer hosts.
This is the start key, so it is always correct to retry with this same key. That simplifies
the ClientScanner logic and also make this sort of coprocessors possible,



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