[jira] Commented: (CASSANDRA-2109) Improve default window size for DES

["Stu Hood (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-2109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12990458#comment-12990458 ] 

Stu Hood commented on CASSANDRA-2109:
-------------------------------------

I'm not prescribing a solution here, but I'd be fine with a hardcoded window size that better minimized the chances of the above case.

> Improve default window size for DES
> -----------------------------------
>
>                 Key: CASSANDRA-2109
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2109
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Stu Hood
>            Priority: Minor
>              Labels: des
>             Fix For: 0.8
>
>
> The window size for DES is currently hardcoded at 100 requests. A larger window means that it takes longer to react to a suddenly slow node, but that you have a smoother transition for scores.
> An example of bad behaviour: with a window of size 100, we saw a case with a failing node where if enough requests could be answered quickly out of cache or bloomfilters, the window might be momentarily filled with 10 ms requests, pushing out requests that had to go disk and took 10 seconds.

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