[Engine-devel] [UX] how to design a bar/line chart?

Alexander Wels awels at redhat.com
Tue Nov 12 14:33:56 UTC 2013 

On Tuesday, November 12, 2013 09:25:34 AM Tomas Jelinek wrote:
> Hey all,
> 
> let me conclude what has been written in this thread to one proposal:
> 
> == From the UX perspective the behavior ==
> - each time the FE will receive new data and this data are different from
> the old ones, visualize it in the chart It means if you will keep pressing
> the refresh button but the data will not change, no new data will be
> visualized (an exception will be the 0 usage) - the amount of data
> visualized will depend on the size of the widget (since the tables are
> resizable). It means that if you make the widget bigger you will not see
> the same chart bigger but more data. - If you make the widget bigger, only
> then the amount of data will start to increase: e.g.
> 
> before resize:
> | /-------\ |
> |
> |/         \|
> 
> after resize:
> | /-------\          |
> |
> |/         \         |
> 
> and only now the new data will start to appear
> 
> == From FE technical point of view ==
> - since I have not found any GWT library which would be acceptable (e.g.
> actively developed and without the need to connect to google servers) and
> given that the required chart is quite simple I guess it would be ok to
> write it by myself. - according to Einav's mail it is ok to use HTML5
> canvas so I would go with writing a new widget using HTML5 canvas
> 

Just to throw out something to think about, we could also in theory generate 
an image on the server side and simply display that image inside the grid (so 
no need for HTML5 canvas or other things like that). The idea being basically 
that when the grid refreshes it makes a request for a new image on the back-
end with the appropriate timeframe and the back-end generates the image which 
is easy to embed inside the grid. 

pros:
* Easy to embed inside grid (just an image tag).
* Works on all browsers, even ones without HTML5 canvas support.
cons:
* More load on the back-end.
* Extra round trips to back-end on refresh.
* Not 'hot' like HTML5 canvas.
* No interactivity if that is something we are interested in.

> == From L&F point of view ==
> - would look pretty much like the one proposed by Malini:
> http://style.org/chartapi/sparklines/
> 
> == From data point of view ==
> - do not do any averages on VDSM side (since it already does them for CPU
> and network and the memory is stable enough) - do not do any averages on
> engine side (since would have to be done for each FE separately and stored
> in session which is a bit overcomplicated. If the user wants to see more
> accurate data, he/she can change the refresh rate) - do not do any
> interpolation since the data are already averaged and we will show only new
> ones
> 
> @Malini,Einav,Eldan,Michal what do you think?
> 
> Tomas
> 
> ----- Original Message -----
> 
> > From: "Michal Skrivanek" <michal.skrivanek at redhat.com>
> > To: "Tomas Jelinek" <tjelinek at redhat.com>, "Dan Kenigsberg"
> > <danken at redhat.com> Cc: "Malini Rao" <mrao at redhat.com>, "Eldan
> > Hildesheim" <ehildesh at redhat.com>, engine-devel at ovirt.org, "info"
> > <info at eldanet.com>
> > Sent: Tuesday, November 12, 2013 11:49:12 AM
> > Subject: Re: [Engine-devel] [UX] how to design a bar/line chart?
> > 
> > On Nov 12, 2013, at 11:18 , Tomas Jelinek <tjelinek at redhat.com> wrote:
> > > So we have looked into the resource usage sampling with mbetak and also
> > > with Michal and it seems that
> > > 
> > > for the CPU usage:
> > > - VDSM polls libvirt to get the runtime statistics of the VM regularly.
> > > The
> > > pooling interval is configured in
> > > 
> > >  vdsm.conf as vm_sample_cpu_interval and by default it is 15 seconds
> > > 
> > > - libvirt returns something we than use to calculate the average CPU
> > > usage
> > > since the last poll
> > > - engine polls VDSM once in 15 seconds to get the current statistics
> > > (the
> > > same 15 seconds is just a coincidence and we can not count on this)
> > > - than the frontend polls the engine each 5-60 seconds (depends on the
> > > refresh rate) and gets the current value from the engine
> > > - the user can press the refresh button anytime to poll the engine again
> > > 
> > > For network usage:
> > > - it should be pretty much the same as the CPU just the VDSM poll
> > > interval
> > > is configured as vm_sample_net_interval and by default it is 5 seconds
> > 
> > Dan, since we poll only every 15s and cpu info is 15s wouldn't it make
> > sense to change the default for network monitoring to 15s as well? it's 2
> > libvirt rounds trip for nothing really. Or does it serve some other
> > purpose?> 
> > > For memory usage:
> > > - guest agent sends a message to VDSM with the memory usage regularly.
> > > The
> > > interval is set in ovirt-guest-agent.conf as heart_beat_rate
> > > 
> > >  and by default it is 5 seconds
> > > 
> > > - the actual value sent by ovirt-guest-agent is the actual value at the
> > > time when the value is sent (e.g. for Linux taken from "cat
> > > /proc/meminfo")
> > > - vdsm is doing no statistics on top of it, just remembers the last
> > > value
> > > taken from ovirt-guest-agent
> > 
> > which is fine, it doesn't change so often and there are typically no
> > spikes
> > 
> > > - the rest of the poling is the same
> > > 
> > > So, visualizing this in some usable form will be quite challenging ;)
> > > I see the following problems:
> > > - if the VDSM gets the data faster than the engine polls it (and most
> > > often
> > > it does) than the info in between will be lost.
> > > 
> > >  The question is how big this problem is and if it is worth solving (I
> > >  would say not for CPU which are averages but maybe yes for memory).
> > >  Other question if there is a way how to solve it since the VDSM can be
> > >  polled by anyone and it does not really care if someone polls it...
> > >  (Michal?)
> > 
> > I'd say not solve it and try to keep it in sync on vdsm side with engine
> > poll, to save unnecessary libvirt calls
> > 
> > > - we can lost some data between frontend<->engine if the polling
> > > interval
> > > of the FE is slower than the polling interval of the engine. This is
> > > something
> > > 
> > >  not really worth solving because the user can set this according to the
> > >  level of detail he/she wants
> > 
> > well, you should average the values in engine in case the FE refresh is
> > >15s. Or add (refresh/15) of them
> 
> It is not that simple since you can have more frontends and not sure if it
> would be a good idea to put this into the session...
> 
> > > - since we will get new info once in ~15 seconds, and the polling of the
> > > FE
> > > is by default 5 seconds, do we want to do some interpolation? Or just
> > > show
> > > the
> > > 
> > >  same value 3 times? Or be smart and show only changed values? (this is
> > >  tricky since there is a chance that it did not change - e.g. constant 0
> > >  mem usage if you have no guest agent)
> > > 
> > > - What if the user starts clicking to the refresh button? Do we want to
> > > keep appending the same value if the engine still has only the old ones?
> > 
> > just add a new line/point every 15s should be ok
> > 
> > Thanks,
> > michal
> > 
> > > Tomas
> > > 
> > > ----- Original Message -----
> > > 
> > >> From: "Tomas Jelinek" <tjelinek at redhat.com>
> > >> To: "Malini Rao" <mrao at redhat.com>
> > >> Cc: "Eldan Hildesheim" <ehildesh at redhat.com>, engine-devel at ovirt.org,
> > >> "info" <info at eldanet.com>
> > >> Sent: Monday, November 11, 2013 4:23:09 PM
> > >> Subject: Re: [Engine-devel] [UX] how to design a bar/line chart?
> > >> 
> > >> 
> > >> 
> > >> ----- Original Message -----
> > >> 
> > >>> From: "Malini Rao" <mrao at redhat.com>
> > >>> To: "Eldan Hildesheim" <ehildesh at redhat.com>
> > >>> Cc: "Tomas Jelinek" <tjelinek at redhat.com>, "info" <info at eldanet.com>,
> > >>> engine-devel at ovirt.org
> > >>> Sent: Monday, November 11, 2013 4:15:50 PM
> > >>> Subject: Re: [Engine-devel] [UX] how to design a bar/line chart?
> > >>> 
> > >>> Is this going to fit in a row of a table? Or are we talking of a more
> > >>> detailed view?
> > >> 
> > >> it should fit into one cell of the table
> > >> 
> > >>> ----- Original Message -----
> > >>> From: "Eldan Hildesheim" <ehildesh at redhat.com>
> > >>> To: "Tomas Jelinek" <tjelinek at redhat.com>
> > >>> Cc: "info" <info at eldanet.com>, engine-devel at ovirt.org
> > >>> Sent: Monday, November 11, 2013 8:01:07 AM
> > >>> Subject: Re: [Engine-devel] [UX] how to design a bar/line chart?
> > >>> 
> > >>> Throw this gif into a browser. This is more or less what I thought.
> > >>> Eldan
> > >>> 
> > >>> ----- Original Message -----
> > >>> From: "Tomas Jelinek" <tjelinek at redhat.com>
> > >>> To: "Eldan Hildesheim" <ehildesh at redhat.com>
> > >>> Cc: "Einav Cohen" <ecohen at redhat.com>, "info" <info at eldanet.com>,
> > >>> engine-devel at ovirt.org
> > >>> Sent: Monday, November 11, 2013 12:03:15 PM
> > >>> Subject: Re: [Engine-devel] [UX] how to design a bar/line chart?
> > >>> 
> > >>> 
> > >>> 
> > >>> ----- Original Message -----
> > >>> 
> > >>>> From: "Eldan Hildesheim" <ehildesh at redhat.com>
> > >>>> To: "Einav Cohen" <ecohen at redhat.com>
> > >>>> Cc: "info" <info at eldanet.com>, engine-devel at ovirt.org
> > >>>> Sent: Sunday, November 10, 2013 3:56:57 PM
> > >>>> Subject: Re: [Engine-devel] [UX] how to design a bar/line chart?
> > >>>> 
> > >>>> Hello all,
> > >>>> We use to have a good solution in the period pre-WPF.
> > >>>> A line chart (used to be in flash) that works like a plotter:
> > >>>> The Line Bar (not bar) had a small animation that shifted all the bar
> > >>>> to
> > >>>> the
> > >>>> left.
> > >>>> When a new data arrived it just added a new line (to the right) and
> > >>>> as I
> > >>>> said
> > >>>> before, in parallel it always shifted slowly to the left.
> > >>> 
> > >>> Any chance you still have some screenshot or mockup so I can imagine
> > >>> it
> > >>> better?
> > >>> 
> > >>>> The animation gives the impression that data is streaming and when a
> > >>>> real
> > >>>> new
> > >>>> data arrives the user gets it very fast.
> > >>>> We have to sync between the animation and the rate of the arrival of
> > >>>> the
> > >>>> data
> > >>>> but this is easy.
> > >>>> If we can't find a good framework it can be created from scratch with
> > >>>> JS,
> > >>>> svg
> > >>>> or canvas.
> > >>> 
> > >>> We need to be careful about what we will use. oVirt is supposed to
> > >>> work
> > >>> on
> > >>> FF
> > >>> 17 [1]
> > >>> but the HTML5 canvas works only since FF23 [2].
> > >>> 
> > >>> @Einav:
> > >>> Is there a chance that we could start support only FF23+ and IE9+
> > >>> (this
> > >>> one
> > >>> is already OK)
> > >>> because of this feature?
> > >>> 
> > >>>> Now regarding its position:
> > >>>> Rollover is good but not enough, we should somehow put it in the
> > >>>> lower
> > >>>> panel
> > >>>> under general or even another tab - (live data).
> > >>> 
> > >>> This is a bit different requirement. The point of this specific is to
> > >>> give
> > >>> a
> > >>> better
> > >>> overview in the main tab. If it will be done we can decide if we want
> > >>> to
> > >>> give
> > >>> more
> > >>> details in sub tabs.
> > >>> 
> > >>>> We could later on have a (live data Tab) in other places as well like
> > >>>> host,
> > >>>> cluster...
> > >>>> Eldan
> > >>> 
> > >>> [1]: http://www.ovirt.org/Download
> > >>> [2]: http://caniuse.com/#feat=canvas
> > >>> 
> > >>>> ----- Original Message -----
> > >>>> From: "Einav Cohen" <ecohen at redhat.com>
> > >>>> To: "Ewoud Kohl van Wijngaarden" <ewoud+ovirt at kohlvanwijngaarden.nl>
> > >>>> Cc: "Alexander Wels" <awels at redhat.com>, "Eldan Hildesheim"
> > >>>> <ehildesh at redhat.com>, engine-devel at ovirt.org, "info"
> > >>>> <info at eldanet.com>
> > >>>> Sent: Friday, November 8, 2013 10:50:10 PM
> > >>>> Subject: Re: [Engine-devel] [UX] how to design a bar/line chart?
> > >>>> 
> > >>>>> ----- Original Message -----
> > >>>>> From: "Ewoud Kohl van Wijngaarden"
> > >>>>> <ewoud+ovirt at kohlvanwijngaarden.nl>
> > >>>>> Sent: Thursday, November 7, 2013 11:44:07 AM
> > >>>>> 
> > >>>>> On Wed, Nov 06, 2013 at 11:45:36AM -0500, Alexander Wels wrote:
> > >>>>>> I suppose we need to answer a few questions before we can go into
> > >>>>>> which
> > >>>>>> library is better:
> > >>>>>> 
> > >>>>>> 1. Do we mind sending data over to Google so Google can render
> > >>>>>> images
> > >>>>>> for
> > >>>>>> us.
> > >>>>> 
> > >>>>> I'd say no. Even from a reliability point of view since users may
> > >>>>> have
> > >>>>> systems that aren't connected to the internet.
> > >>>> 
> > >>>> +1
> > >>>> 
> > >>>>> (Though I don't know how well oVirt handles this currently.)
> > >>>> 
> > >>>> AFAIK - oVirt is handling it ('it' ==  having no internet connection)
> > >>>> well.
> > >>>> _______________________________________________
> > >>>> Engine-devel mailing list
> > >>>> Engine-devel at ovirt.org
> > >>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> > >>> 
> > >>> _______________________________________________
> > >>> Engine-devel mailing list
> > >>> Engine-devel at ovirt.org
> > >>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> > >> 
> > >> _______________________________________________
> > >> Engine-devel mailing list
> > >> Engine-devel at ovirt.org
> > >> http://lists.ovirt.org/mailman/listinfo/engine-devel
> 
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