Cyril Scetbon created CASSANDRA-7731:
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Summary: Average 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
Priority: Minor
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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