[jira] [Comment Edited] (CASSANDRA-7402) limit the on heap memory available to requests

["T Jake Luciani (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-7402?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14032878#comment-14032878 ] 

T Jake Luciani edited comment on CASSANDRA-7402 at 6/16/14 8:21 PM:
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This isn't going to fix the underlying issue (reads/queries are overcapacity) but it will tell an operator that reads are too high vs just wondering what's happening to the system.

Similar to the purpose of memtable_cleanup_threashold




was (Author: tjake):
This isn't going to fix the underlying issue (reads/queries are overcapacity but it will tell an operator that reads are too high vs just wondering what's happening to the system).

Similar to the purpose of memtable_cleanup_threashold



> 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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