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https://issues.apache.org/jira/browse/HBASE-8285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13625819#comment-13625819
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Lars Hofhansl commented on HBASE-8285:
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I finally understand the problem. So what you want to happen is that the first
time the region has moved it is OK for the Get to fail, as long as it succeeds
if you try again.
Patch makes sense, even though this is a bit of an exotic usecase. Can't you
just try twice with a short timeout?
Also "re-tries" is misnamed. If set to 1 we only try once (we don't try and
then retry once). If set to 0, we don't try at all. Should be called "tries",
but anyway, we're not going to change that.
+1 on patch
> HBaseClient never recovers for single HTable.get() calls with no retries when
> regions move
> ------------------------------------------------------------------------------------------
>
> Key: HBASE-8285
> URL: https://issues.apache.org/jira/browse/HBASE-8285
> Project: HBase
> Issue Type: Bug
> Components: Client
> Affects Versions: 0.94.6.1
> Reporter: Varun Sharma
> Assignee: Varun Sharma
> Priority: Critical
> Fix For: 0.98.0, 0.94.7, 0.95.1
>
> Attachments: 8285-0.94.txt, 8285-0.94-v2.txt, 8285-trunk.txt,
> 8285-trunk-v2.txt
>
>
> Steps to reproduce this bug:
> 1) Gracefull restart a region server causing regions to get redistributed.
> 2) Client call to this region keeps failing since Meta Cache is never purged
> on the client for the region that moved.
> Reason behind the bug:
> 1) Client continues to hit the old region server.
> 2) The old region server throws NotServingRegionException which is not
> handled correctly and the META cache entries are never purged for that server
> causing the client to keep hitting the old server.
> The reason lies in ServerCallable code since we only purge META cache entries
> when there is a RetriesExhaustedException, SocketTimeoutException or
> ConnectException. However, there is no case check for
> NotServingRegionException(s).
> Why is this not a problem for Scan(s) and Put(s) ?
> a) If a region server is not hosting a region/scanner, then an
> UnknownScannerException is thrown which causes a relocateRegion() call
> causing a refresh of the META cache for that particular region.
> b) For put(s), the processBatchCallback() interface in HConnectionManager is
> used which clears out META cache entries for all kinds of exceptions except
> DoNotRetryException.
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