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https://issues.apache.org/jira/browse/HBASE-2692?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12890897#action_12890897
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Jean-Daniel Cryans commented on HBASE-2692:
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My first pass on the document, would be nice if the doc was on rb.
bq. - Master startup determines whether this is startup or failover by
counting the number of RS nodes in ZK.
FWIW there's also a znode called "shutdown" that, if present, means that the
cluster is up and running.
bq. - Master waits for the minimum number of RS to be available to be
assigned regions.
I'd be interested to see your thoughts about determining the minimum number of
RSs. Also how do you handle the assignment of ROOT and META? What's the chance
that there's always enough RSs that reported in once both catalog regions are
assigned?
{quote}
Periodically, and when there are not any regions in transition, a load
balancer will run and move regions around to balance cluster load
{quote}
It's not clear to me why you have to wait. Then you wrote:
bq. - Load balancer blocks until there are no regions in transition.
So once the load balancer is started, do we block regions going in transition?
bq. - Master sends RPCs to the source RSs, telling them to CLOSE the
regions.
What happens if a region splits while load balancing is running?
bq. - Master finds all regions of the table.
Same question, what do you do if a region splits just after that? Won't you be
missing 2 regions and giving a CLOSE rpc that's invalid?
> Master rewrite and cleanup for 0.90
> -----------------------------------
>
> Key: HBASE-2692
> URL: https://issues.apache.org/jira/browse/HBASE-2692
> Project: HBase
> Issue Type: Improvement
> Reporter: Jonathan Gray
> Assignee: Jonathan Gray
> Priority: Blocker
> Fix For: 0.90.0
>
> Attachments: BRANCH_NOTES.txt
>
>
> This is the parent issue for master changes targeted at 0.90 release.
> Changes done as part of this issue grew out of work done over in HBASE-2485
> to move region transitions into ZK.
> In addition to that work, this issue will include general HMaster and
> ZooKeeper refactorings and cleanups.
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