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https://issues.apache.org/jira/browse/HBASE-18036?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stephen Yuan Jiang updated HBASE-18036:
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Attachment: HBASE-18036.v1-branch-1.1.patch
> Data locality is not maintained after cluster restart or SSH
> ------------------------------------------------------------
>
> Key: HBASE-18036
> URL: https://issues.apache.org/jira/browse/HBASE-18036
> Project: HBase
> Issue Type: Bug
> Components: Region Assignment
> Affects Versions: 1.4.0, 1.3.1, 1.2.5, 1.1.10
> Reporter: Stephen Yuan Jiang
> Assignee: Stephen Yuan Jiang
> Attachments: HBASE-18036.v0-branch-1.1.patch,
> HBASE-18036.v1-branch-1.1.patch
>
>
> After HBASE-2896 / HBASE-4402, we think data locality is maintained after
> cluster restart. However, we have seem some complains about data locality
> loss when cluster restart (eg. HBASE-17963).
> Examining the AssignmentManager#processDeadServersAndRegionsInTransition()
> code, for cluster start, I expected to hit the following code path:
> {code}
> if (!failover) {
> // Fresh cluster startup.
> LOG.info("Clean cluster startup. Assigning user regions");
> assignAllUserRegions(allRegions);
> }
> {code}
> where assignAllUserRegions would use retainAssignment() call in LoadBalancer;
> however, from master log, we usually hit the failover code path:
> {code}
> // If we found user regions out on cluster, its a failover.
> if (failover) {
> LOG.info("Found regions out on cluster or in RIT; presuming failover");
> // Process list of dead servers and regions in RIT.
> // See HBASE-4580 for more information.
> processDeadServersAndRecoverLostRegions(deadServers);
> }
> {code}
> where processDeadServersAndRecoverLostRegions() would put dead servers in SSH
> and SSH uses roundRobinAssignment() in LoadBalancer. That is why we would
> see loss locality more often than retaining locality during cluster restart.
> Note: the code I was looking at is close to branch-1 and branch-1.1.
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