[jira] [Commented] (SOLR-16073) totalTime metric should be milliseconds (not nano)

["Andrzej Bialecki (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-16073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17503586#comment-17503586 ] 

Andrzej Bialecki commented on SOLR-16073:
-----------------------------------------

Removing the conversion may have been a mistake, we should consistently report time intervals using the same units - currently we report the intervals inside histograms in milliseconds, and the elapsed times of Timers we report in nanoseconds.

Changing the units may have some back-compat consequences, not sure how to address them. Also, I can't say whether this metric is useful to be included by default in the exporter - generally speaking, since exporting the metrics via Prometheus exporter is a relatively heavyweight process IMHO we should attempt to cut down the number of exported metrics to a bare minimum (whatever that means ;) ).

> totalTime metric should be milliseconds (not nano)
> --------------------------------------------------
>
>                 Key: SOLR-16073
>                 URL: https://issues.apache.org/jira/browse/SOLR-16073
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>          Components: metrics
>            Reporter: David Smiley
>            Priority: Minor
>
> I observed that the "totalTime" metric has been a nanosecond number in recent years, yet once upon a time it was milliseconds. This change was very likely inadvertent. Our prometheus solr-exporter-config.xml shows that it thinks it's milliseconds. It's not; RequestHandlerBase increments this counter by "elapsed", the response of timer.stop() -- nanoseconds. Years ago it had invoked {{MetricUtils.nsToMs}} but it appears [~ab] removed this as a part of other changes in 2017 sometime -- https://github.com/apache/solr/commit/d8df9f8c9963c2fc1718fd471316bf5d964125ba
> Also, I question the value/purpose of this metric.  Is it so useful that it deserves to be among our relatively few metrics exported in our default prometheus exporter config?  It's been there since the initial config but I wonder why anyone wants it.



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