Prototyping Fedora widgets framework

[Ralph Bean]

On Sun, Mar 15, 2015 at 03:49:29PM +0530, Ratnadeep Debnath wrote:
> Hi all,
> 
> As discussed over IRC, I am working on prototyping a framework to
> power generic widgets for Fedora. This framework will allow writing
> widgets for Fedora in Python, mostly.

In general, I think this is a cool idea.  We expose *lots* of raw
information via datagrepper.. but it's just a pile of data.  Providing
someway for people to query for more structured, preprocessed
information could be neat.

> Basic components
> ==============
> Dispatcher
> ----------------
> Dispatcher is part of a daemon process which keeps on listening to
> fedmsg messages and invoking widgets to save data as needed. Widgets
> can be tied to the dispatcher using signals, observer patterns, etc.
> 
> Widget
> ----------
> I define a widget implementation as a standalone entity which knows:
> 1. How to handle raw fedmsg data, format it and save it for enabling
> faster query

I really like part (1).  We could pre-process all kinds of data.  Keep
statistics and make them all available via API.

> 2. Render data from saved data. 

I'm not sure how I feel about part (2).  It seems to me like it will
introduce a higher overhead to future changes to the service and more
of the same for people trying to use it.

What if:

- Someone wants to style their widget differently?
- Combine the data from two widgets into some other widget?
- Use only part of the data typically associated with one widget.

To do any of those, would they need to submit a patch to our
server-side code, and then have it be reviewed, released and deployed
before they can make use of it?

How do you feel instead about splitting it up into two pieces:
server-side data denormalization and client side visualization (via a
python lib or maybe better, a js lib?).  That way people can query for
the grouped/collated data and then present it however they like.  Just
a thought.

> API
> ------
> Provide REST interface to fetch data from a widget for a particular
> entity, say, badges info for a user for UserBadgesWidget.
> 
> I have started working on a prototype based on the Observer design
> pattern here[1].
> 
> Please provide your feedback on the same. I am also thinking to work
> on a prototype based on signals, to see which prototype allows us to
> expose friendly interfaces for writing widgets.
> 
> [1]: https://github.com/rtnpro/fedwidgets/blob/master/fedwidgets/prototypes/observer_pattern.py

Looks like a good start :)
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