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https://issues.apache.org/jira/browse/CASSANDRA-12876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15663718#comment-15663718
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Per Otterström commented on CASSANDRA-12876:
--------------------------------------------
Overflow don't happen at the start of the 30 minute cycle because 1) it takes a
while to build up high enough values in the individual buckets and 2) values
collected at the end of the 30-minute cycle will have much higher forward-decay
weight which cause bucket values to build up much faster.
In your case you are seeing this at the last 3 minutes of the 30-minute cycle,
because only then will the forward-decay weight be high enough.
> Negative mean write latency
> ---------------------------
>
> Key: CASSANDRA-12876
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12876
> Project: Cassandra
> Issue Type: Bug
> Components: Observability
> Reporter: Kévin LOVATO
> Assignee: Per Otterström
> Fix For: 2.2.9
>
> Attachments: 12876-2.2.txt, negative_mean.png,
> negative_mean_details.PNG, negative_mean_periodicity.PNG
>
>
> The mean write latency returned by JMX turns negative every 30 minutes. As
> the attached screenshots show, the value turns negative every 30 minutes
> after the startup of the node.
> We did not experience this behavior in 2.1.16.
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