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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17462) Investigate using sliding window for read/write request costs in StochasticLoadBalancer
Date Thu, 19 Jan 2017 23:08:26 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17462?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15830789#comment-15830789

Ted Yu commented on HBASE-17462:

+      for (RegionLoad rl : regionLoadList) {
+        double current = getCostFromRl(rl);
+        if (previous != null) {
+          cost += current - previous;
+        }
+        previous = current;
(Through debug logging) what is length of regionLoadList for the read / write requests ?
The average length would give us some idea how many samples are taken for the sliding window.

Can you share (improved) performance when you tested the change on your cluster ?


> Investigate using sliding window for read/write request costs in StochasticLoadBalancer
> ---------------------------------------------------------------------------------------
>                 Key: HBASE-17462
>                 URL: https://issues.apache.org/jira/browse/HBASE-17462
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Ted Yu
>            Assignee: Tim Brown
>              Labels: patch
>         Attachments: HBASE-17642.patch
> In the thread, http://search-hadoop.com/m/HBase/YGbbyUZKXWALkX1, Timothy was asking whether
the read/write request costs in StochasticLoadBalancer should be calculated as rates.
> This makes sense since read / write load on region server tends to fluctuate over time.
Using sliding window would reflect more recent trend in read / write load.
> Some factors to consider:
> The data structure used by StochasticLoadBalancer should be concise. The
> number of regions in a cluster can be expected to approach 1 million. We
> cannot afford to store long history of read / write requests in master.
> Efficiency of cost calculation should be high - there're many cost
> functions the balancer goes through, it is expected for each cost function
> to return quickly. Otherwise we would not come up with proper region
> movement plan(s) in time.

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