[jira] [Commented] (HBASE-3373) Allow regions to be load-balanced by table

["Lars Hofhansl (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-3373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13178606#comment-13178606 ] 

Lars Hofhansl commented on HBASE-3373:
--------------------------------------

Looks good to me (as far as I understand the balancing code).
Minor nits:
* Should "ensemble" be "dummytable" (or something) and be defined as constant?
* Why:
{code}
if (!svrToRegions.containsKey(e.getKey())) {
  regions = new ArrayList<HRegionInfo>();
  svrToRegions.put(e.getKey(), regions);
} else {
  regions = svrToRegions.get(e.getKey());
}
{code}
instead of:
{code}
regions = svrToRegions.get(e.getKey());
if (regions == null) {
  regions = new ArrayList<HRegionInfo>();
  svrToRegions.put(e.getKey(), regions);
}
{code}
serverName can't be null here, correct?

                
> Allow regions to be load-balanced by table
> ------------------------------------------
>
>                 Key: HBASE-3373
>                 URL: https://issues.apache.org/jira/browse/HBASE-3373
>             Project: HBase
>          Issue Type: Improvement
>          Components: master
>    Affects Versions: 0.20.6
>            Reporter: Ted Yu
>             Fix For: 0.94.0
>
>         Attachments: 3373.txt, HbaseBalancerTest2.java
>
>
> From our experience, cluster can be well balanced and yet, one table's regions may be badly concentrated on few region servers.
> For example, one table has 839 regions (380 regions at time of table creation) out of which 202 are on one server.
> It would be desirable for load balancer to distribute regions for specified tables evenly across the cluster. Each of such tables has number of regions many times the cluster size.

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