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https://issues.apache.org/jira/browse/HBASE-2189?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12832189#action_12832189
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stack commented on HBASE-2189:
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+1 on patch. I tried various combinations of shutdown of servers carrying root
and meta and client kept-on keeping-on. I'd say go commit it.
> HCM trashes meta cache even when not needed
> -------------------------------------------
>
> Key: HBASE-2189
> URL: https://issues.apache.org/jira/browse/HBASE-2189
> Project: Hadoop HBase
> Issue Type: Improvement
> Affects Versions: 0.20.3
> Reporter: Jean-Daniel Cryans
> Assignee: Jean-Daniel Cryans
> Fix For: 0.20.4, 0.21.0
>
> Attachments: HBASE-2189-v2.patch, HBASE-2189.patch
>
>
> I was investigating HBASE-2175 when I saw that we are doing a lot more ROOT
> lookups than needed. For example, typical output of PE seqWrite during split:
> {code}
> client.HConnectionManager$TableServers: Removed TestTable,,1265524229864 for
> tableName=TestTable from cache because of 0000380292
> client.HConnectionManager$TableServers: locateRegionInMeta attempt 0 of 10
> failed; retrying after sleep of 1000 because:
> No server address listed in .META. for region
> TestTable,0000086976,1265524283534
> client.HConnectionManager$TableServers: Removed .META.,,1 for
> tableName=.META. from cache because of TestTable,0000380292,99999999999999
> client.HConnectionManager$TableServers: Cached location for .META.,,1 is
> 192.168.1.103:56279
> client.HConnectionManager$TableServers: locateRegionInMeta attempt 1 of 10
> failed; retrying after sleep of 1000 because:
> No server address listed in .META. for region
> TestTable,0000086976,1265524283534
> client.HConnectionManager$TableServers: Removed .META.,,1 for
> tableName=.META. from cache because of TestTable,0000380292,99999999999999
> client.HConnectionManager$TableServers: Cached location for .META.,,1 is
> 192.168.1.103:56279
> client.HConnectionManager$TableServers: Cached location for
> TestTable,0000086976,1265524283534 is 192.168.1.103:56279
> {code}
> So why exactly are we removing .META.,,1 from the cache? Because a row didn't
> have the right address? So that means we did contact .META. but the
> information we got is still stall because the split isn't finished yet... but
> why should that result in trashing the cache?
> Because we don't differentiate between NSRE / WRE from other exceptions like
> empty server address. This happens a lot more often now that the Master
> clears that cell when a region is closed instead of keeping the old value.
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