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[Thierry Carrez <thierry.carrez+lp@xxxxxxxxx>]

** Changed in: horizon
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1243716

Title:
  metering line charts not always scaled for duration selected

Status in OpenStack Dashboard (Horizon):
  Fix Released

Bug description:
  When the duration requested for charting a meter exceeds the time-
  range over which samples are actually available, the resource usage
  chart isn't scaled over the actual duration selected.

  For example, suppose samples for a particular meter have only been
  gathered by ceilometer over the past 6 days (such a scenario would not
  be atypical for a relatively fresh openstack deployment).

  If the user requests that this meter is graphed over the Last Week,
  they see the entire width of the chart taken up by the 6 days for
  which there is actual data. Not a big issue as 6 days is a close
  approximation of a week.

  If they then change the duration requested to the next option in the
  Period dropdown, i.e. Last 15 days, the data is still charted over the
  same approximate 6 day duration. The shape of the graph changes
  somewhat, but only because the timeslice length requested of
  ceilometer has changed (as horizon arbitrary sets this to 1/400th of
  the duration).

  If the users continues to choose progressively longer durations (Last
  30 Days, Last Year) the pattern is repeated.

  So in effect, changing the duration just gives a more coarse-grained
  representation of the *same* data. Intuitively the expectation would
  be for the x-axis of the graph to be scaled to the entire duration
  selected, and if there isn't data available for the entire duration,
  then the trend line should be rendered only for a portion of this
  width.

  I'll attach screenshots illustrating this trend.

  Proposed solutions:

  1. Scale the x-axis of the line chart over the entire duration
  requested, but only render the trend line over the subset of time for
  which there is actual data available. If the rickshaw toolkit doesn't
  support this behaviour directly, maybe it could be tricked into doing
  so by injecting invisible datapoints across the entire time range.

  2. Pre-query for the first and last datapoints within each range, then
  make the Period dropdown list context sensitive, such that the options
  available only reflect the durations for which there is actual data.
  In the example scenario above, this would be Last Day, Last Week and
  Other (whereas Last 15 Days, Last 30 Days and Last Year add nothing to
  the mix).

  Option #1 would be preferred I think, whereas option #2 is suggested
  only as a fallback if rickshaw is too inflexible.

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