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  1. Percona Monitoring and Management
  2. PMM-2698

Misleading Graphs for Rare Events

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    Details

    • Type: Bug
    • Status: Done
    • Priority: Medium
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 1.13.0
    • Component/s: Grafana Dashboards
    • Labels:
      None

      Description

      One of the important type of data we need to display is something which I
      would call "rare events" - this is something which happens rarely, the
      counter might be incremented only by one periodically but it is important
      so it is not lost.

      Currently it looks like the visualization is sometimes loosing this data.

      Here is example for TokuDB Checkpoints where checkpoint should be taken
      approximately every 1 minute. If this is not happening for some reason
      this would be important issue to investigate

      Yet as this see from this graph in Advanced Data Explorations while we see
      the Variable being incremented (top graph) the graph below misses some of
      the regular "spikes" giving impression what Checkpoints were not taking
      from 9:17 to 9:23

      https://pmmdemo.percona.com/graph/d/1oz9QMHmk/advanced-data-exploration?orgId=1&from=now-1h&to=now&var-metric=mysql_global_status_tokudb_checkpoint_taken&var-interval=5s&var-host=ps57&refresh=1m

      (This link may stop working as data get purged but you should see the same
      picking recent period)

      Now what is interesting as you go ahead and zoom in such empty period we
      see the data

      The formula we're using is this:

      Which means we're grouping data by $interval rate, using same step as
      interval and using 1/1 resolutions so all data points should be plotted.

      I wonder however with this being called "Min Step" now if we may end up
      having different step being used ?

      As this happens with "auto" interval as well this also may be some interval
      fitting logic.


      Peter Zaitsev, CEO, Percona

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              • Assignee:
                Unassigned
                Reporter:
                pz Peter Zaitsev
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