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Chris Lohfink commented on CASSANDRA-7731:
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bq. we don't want to change it to be the maximum value since the application
started
maximum value since the application started is the only option. The only thing
the reservoir is used for is for the percentiles like 50th, 75th, 90th etc.
Only thing you can change in theory is to use a uniform reservoir instead of a
EWMA reservoir to be the same (since start of app instead of last 5 min). The
min,max,count,sum,std dev etc are all based on since C* started.
In the newer versions of Metrics all the values would be computed from the
reservoir snapshot so it would follow the 5 min-ish result.
> 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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