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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7402) limit the on heap memory available to requests
Date Mon, 16 Jun 2014 18:04:02 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7402?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14032693#comment-14032693
] 

Jonathan Ellis commented on CASSANDRA-7402:
-------------------------------------------

But active memory != garbage created.  I'm not saying it's a bad idea, but I'm skeptical that
it will work well. :)

> limit the on heap memory available to requests
> ----------------------------------------------
>
>                 Key: CASSANDRA-7402
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7402
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: T Jake Luciani
>             Fix For: 3.0
>
>
> When running a production cluster one common operational issue is quantifying GC pauses
caused by ongoing requests.
> Since different queries return varying amount of data you can easily get your self into
a situation where you Stop the world from a couple of bad actors in the system.  Or more likely
the aggregate garbage generated on a single node across all in flight requests causes a GC.
> We should be able to set a limit on the max heap we can allocate to all outstanding requests
and track the garbage per requests to stop this from happening.  It should increase a single
nodes availability substantially.
> In the yaml this would be
> {code}
> total_request_memory_space_mb: 400
> {code}
> It would also be nice to have either a log of queries which generate the most garbage
so operators can track this.  Also a histogram.



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