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https://issues.apache.org/jira/browse/CASSANDRA-6682?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paulo Gaspar updated CASSANDRA-6682:
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Attachment: 6682.txt
The attached files contains all necessary changes.
> Loss of precision under concurrent access on o.a.c.utils.EstimatedHistogram
> methods
> -----------------------------------------------------------------------------------
>
> Key: CASSANDRA-6682
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6682
> Project: Cassandra
> Issue Type: Bug
> Reporter: Paulo Gaspar
> Priority: Minor
> Fix For: 1.2.16, 2.0.6
>
> Attachments: 6682.txt
>
>
> On method getBuckets(), under concurrent use of an instance, the value of a
> "buckets" variable element might change between its access on the 1st for
> cycle and its access on the 2nd, when it is reset to 0. This means that, if
> one collects metrics by repeatedly calling estHist.getBuckets(true), (e.g.:
> to sum its values) it will miss counting some values added to "buckets"
> entries between that 1st and 2nd access.
> On method mean(), if the i-th entry of "buckets" changes value between the
> 1st and 2nd access inside the for cycle, than the "elements" and "sum"
> accumulators are not working with the same values for that entry. It is more
> precise (and faster) to use a local variable to read the value just once.
> Not an error but a semantic improvement: at my initial read of this class, I
> thought the "buckets" and "bucketOffsets" fields could change length. Such
> perception can be avoided by making the "bucketOffsets" field final.
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