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From "huaxiang sun (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18005) read replica: handle the case that region server hosting both primary replica and meta region is down
Date Tue, 06 Jun 2017 16:02:18 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18005?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16039151#comment-16039151

huaxiang sun commented on HBASE-18005:

Thanks [~tedyu@apache.org]. The failed unittest TestReplicasClient, I run locally with my
patch on branch-1, it passed. The findbug warning is complaining 
RV	Return value of java.util.concurrent.CountDownLatch.await(long, TimeUnit) ignored in org.apache.hadoop.hbase.regionserver.HRegionServer.initializeZooKeeper()

    if (this.initLatch != null) {
      this.initLatch.await(20, TimeUnit.SECONDS);


This is the existing code which is not touched by this patch. We can check the return value
and log something to get rid of the findbug warning.

> read replica: handle the case that region server hosting both primary replica and meta
region is down
> -----------------------------------------------------------------------------------------------------
>                 Key: HBASE-18005
>                 URL: https://issues.apache.org/jira/browse/HBASE-18005
>             Project: HBase
>          Issue Type: Bug
>            Reporter: huaxiang sun
>            Assignee: huaxiang sun
>         Attachments: HBASE-18005-branch-1-v001.patch, HBASE-18005-master-001.patch, HBASE-18005-master-002.patch,
HBASE-18005-master-003.patch, HBASE-18005-master-004.patch, HBASE-18005-master-005.patch,
> Identified one corner case in testing  that when the region server hosting both primary
replica and the meta region is down, the client tries to reload the primary replica location
from meta table, it is supposed to clean up only the cached location for specific replicaId,
but it clears caches for all replicas. Please see
> https://github.com/apache/hbase/blob/master/hbase-client/src/main/java/org/apache/hadoop/hbase/client/ConnectionImplementation.java#L813
> Since it takes some time for regions to be reassigned (including meta region), the following
may throw exception
> https://github.com/apache/hbase/blob/master/hbase-client/src/main/java/org/apache/hadoop/hbase/client/RpcRetryingCallerWithReadReplicas.java#L173
> This exception needs to be caught and  it needs to get cached location (in this case,
the primary replica's location is not available). If there are cached locations for other
replicas, it can still go ahead to get stale values from secondary replicas.
> With meta replica, it still helps to not clean up the caches for all replicas as the
info from primary meta replica is up-to-date.

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