Better visualization for current state of health

[Sean Dague]

On the OpenStack Health front page there are currently 2 line graphs, which mostly don't tell you want is going on. Data failures aren't really line graphs, they are interesting only as aggregates.

What you really want to know is "what's the failure rate trends" and "how sure are we of that".

What the failure rate trends is would be best expressed as stacked bar graphs (pass/fail). You also want to know, at the same time, how sure you are of that number. One way that could be done is with opacity. If we make the bars more transparent if we have less than a reasonable amount of data, that would be extremely useful.

[Tim Buckley (timothy-jas-buckley)]

This is an interesting idea. Do you think this chart could replace the two charts we have now? I'd definitely be interested in combining them, since they're essentially showing exactly the same data while taking up almost the entire front page.

Also, it looks like nvd3 does support stacked bar charts, so this should be technically feasible. I believe we can also pass in transparency as part of the color field we're already using when we generate the chart data. Example is here: http://jsfiddle.net/rustybailey/z4aZ4/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/288251

[Tim Buckley (timothy-jas-buckley)]

I put together a quick patch to demo this idea (screenshots attached). I think this definitely does a better job showing trends directly since you don't have to mentally combine the two charts, although I think there's still some tweaking to do.

A few areas to improve for sure:
 - opacity is calculated a bit strangely ... I'm sure there's a better way than what I used
 - we'll need to play with period size vs resolution, I think 7 days at hour resolution is too dense?
 - this will need a legend of some sort, it isn't very self explanatory