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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-12561) Replicas of regions can be cached from different instances of the table in MetaCache
Date Sat, 22 Nov 2014 02:45:33 GMT
Enis Soztutar created HBASE-12561:

             Summary: Replicas of regions can be cached from different instances of the table
in MetaCache
                 Key: HBASE-12561
                 URL: https://issues.apache.org/jira/browse/HBASE-12561
             Project: HBase
          Issue Type: Sub-task
            Reporter: Enis Soztutar
            Assignee: Enis Soztutar
             Fix For: 2.0.0

In testing, we have observed that if a client caches some regions with replicas in MetaCache,
and then the table is recreated, the cache does not get invalidated. Upon caching more entries
from a new instance of the table we can have entries for replicas from different instances
of a table (remember that metacache is row based)

On async wal replay (HBASE-11568), we have an elaborate mechanism to track region replica
locations and skip replaying wal entries if the current region replica is not the same region
replica from the original wal edit. This prevents replaying entries of older tables with the
same name to the region replicas as well as replaying older entries from split (or merged)
regions from old parent to new daughters.
Trace level logging in my test setup showed that we were skipping some entries because of
a case, where we would have region locations (of the same range) cached from different instances
of the table (meaning some replicas are from already deleted table vs some entries from new
table). This was causing superfluous skipping entries.

The fix can be when we are merging entries for the same range, we simply check the other entries
and delete those that do not match the new region id.

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