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From "Robert Stupp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7731) Get max values for live/tombstone cells per slice
Date Tue, 16 Sep 2014 06:10:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7731?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14135024#comment-14135024
] 

Robert Stupp commented on CASSANDRA-7731:
-----------------------------------------

Seems that the fix is committed to [release 3.1.0|http://search.maven.org/#artifactdetails|io.dropwizard.metrics|metrics-core|3.1.0|bundle].
But it would need some refactoring (more than package renames) in C* code to adopt that new
version. I'll take stab on this to a) consistently verify it with currently used, b) check
whether this is fixed in 3.1.0 and c) determine whether it's "safe" to adopt it in 2.1 or
whether it needs to wait for 3.0. Sorry for the late answer.

> Get max values for live/tombstone cells per slice
> -------------------------------------------------
>
>                 Key: CASSANDRA-7731
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7731
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Cyril Scetbon
>            Assignee: Robert Stupp
>            Priority: Minor
>             Fix For: 2.1.1
>
>         Attachments: 7731-2.0.txt, 7731-2.1.txt
>
>
> I think you should not say that slice statistics are valid for the [last five minutes
|https://github.com/apache/cassandra/blob/cassandra-2.0/src/java/org/apache/cassandra/tools/NodeCmd.java#L955-L956]
in CFSTATS command of nodetool. I've read the documentation from yammer for Histograms and
there is no way to force values to expire after x minutes except by [clearing|http://grepcode.com/file/repo1.maven.org/maven2/com.yammer.metrics/metrics-core/2.1.2/com/yammer/metrics/core/Histogram.java#96]
it . The only thing I can see is that the last snapshot used to provide the median (or whatever
you'd used instead) value is based on 1028 values.
> I think we should also be able to detect that some requests are accessing a lot of live/tombstone
cells per query and that's not possible for now without activating DEBUG for SliceQueryFilter
for example and by tweaking the threshold. Currently as nodetool cfstats returns the median
if a low part of the queries are scanning a lot of live/tombstone cells we miss it !



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