mediagoblin/READMEish.org

#+latex_header: \documentclass[12pt]{article}
#+latex_header: \usepackage[margin=1in]{geometry}
#+OPTIONS: ^:nil

GNU MediaGoblin

* About

What is MediaGoblin?  I'm shooting for:

 - Initially, a place to store all your photos that's as awesome as,
   more awesome than, existing proprietary solutions
 - Later, a place for all sorts of media, such as video, music, etc
   hosting.
 - Federated, like statusnet/ostatus (we should use ostatus, in fact!)
 - Customizable
 - A place for people to collaborate and show off original and derived
   creations
 - Free, as in freedom.  Under the GNU AGPL, v3 or later.  Encourages
   free formats and free licensing for content, too.

Wow!  That's pretty ambitious.  Hopefully we're cool enough to do it.
I think we can.

It's also necessary, for multiple reasons.  Centralization and
proprietization of media on the internet is a serious problem and
makes the web go from a system of extreme resilience to a system
of frightening fragility.  People should be able to own their data.
Etc.  If you're reading this, chances are you already agree though. :)

* Milestones

Excepting the first, not necessarily in this order.

** Basic image hosting
** Multi-media hosting (including video and audio)
** API(s)
** Federation

Maybe this is 0.2 :)

** Plugin system

* Technology

I have a pretty specific set of tools that I expect to use in this
project.  Those are:

 - *[[http://python.org/][Python]]:* because I love, and know well, the language
 - *[[http://www.mongodb.org/][MongoDB]]:* a "document database".  Because it's extremely flexible
   (and scales up well, but I guess not down well)
 - *[[http://namlook.github.com/mongokit/][MongoKit]]:* a lightweight ORM for mongodb.  Helps us define our
   structures better, does schema validation, schema evolution, and
   helps make things more fun and pythonic.
 - *[[http://jinja.pocoo.org/docs/][Jinja2]]:* for templating.  Pretty much django templates++ (wow, I
   can actually pass arguments into method calls instead of tediously
   writing custom tags!)
 - *[[http://wtforms.simplecodes.com/][WTForms]]:* for form handling, validation, abstraction.  Almost just
   like Django's templates, 
 - *[[http://pythonpaste.org/webob/][WebOb]]:* gives nice request/response objects (also somewhat djangoish)
 - *[[http://pythonpaste.org/deploy/][Paste Deploy]] and [[http://pythonpaste.org/script/][Paste Script]]:* as the default way of configuring
   and launching the application.  Since MediaGoblin will be fairly
   wsgi minimalist though, you can probably use other ways to launch
   it, though this will be the default.
 - *[[http://routes.groovie.org/][Routes]]:* for URL routing.  It works well enough.
 - *[[http://jquery.com/][JQuery]]:* for all sorts of things on the javascript end of things,
   for all sorts of reasons.
 - *[[http://beaker.groovie.org/][Beaker]]:* for sessions, because that seems like it's generally
   considered the way to go I guess.
 - *[[http://somethingaboutorange.com/mrl/projects/nose/1.0.0/][nose]]:* for unit tests, because it makes testing a bit nicer.
 - *[[http://celeryproject.org/][Celery]]:* for task queueing (think resizing images, encoding
   video) because some people like it, and even the people I know who
   don't don't seem to know of anything better :)
 - *[[http://www.rabbitmq.com/][RabbitMQ]]:* for sending tasks to celery, because I guess that's
   what most people do.  Might be optional, might also let people use
   MongoDB for this if they want.

** Why python

Because I (Chris Webber) know Python, love Python, am capable of
actually making this thing happen in Python (I've worked on a lot of
large free software web applications before in Python, including
[[http://mirocommunity.org/][Miro Community]], the [[http://miroguide.org][Miro Guide]], a large portion of
[[http://creativecommons.org/][Creative Commons' site]], and a whole bunch of things while working at
[[http://www.imagescape.com/][Imaginary Landscape]]).  I know Python, I can make this happen in
Python, me starting a project like this makes sense if it's done in
Python.

You might say that PHP is way more deployable, that rails has way more
cool developers riding around on fixie bikes, and all of those things
are true, but I know Python, like Python, and think that Python is
pretty great.  I do think that deployment in Python is not as good as
with PHP, but I think the days of shared hosting are (thankfully)
coming to an end, and will probably be replaced by cheap virtual
machines spun up on the fly for people who want that sort of stuff,
and Python will be a huge part of that future, maybe even more than
PHP will.  The deployment tools are getting better.  Maybe we can use
something like Silver Lining.  Maybe we can just distribute as .debs
or .rpms.  We'll figure it out.

But if I'm starting this project, which I am, it's gonna be in Python.

** Why mongodb

In case you were wondering, I am not a NOSQL fanboy, I do not go
around telling people that MongoDB is web scale.  Actually my choice
for MongoDB isn't scalability, though scaling up really nicely is a
pretty good feature and sets us up well in case large volume sites
eventually do use MediaGoblin.  But there's another side of
scalability, and that's scaling down, which is important for
federation, maybe even more important than scaling up in an ideal
universe where everyone ran servers out of their own housing.  As a
memory-mapped database, MongoDB is pretty hungry, so actually I spent
a lot of time debating whether the inability to scale down as nicely
as something like SQL has with sqlite meant that it was out.

But I decided in the end that I really want MongoDB, not for
scalability, but for flexibility.  Schema evolution pains in SQL are
almost enough reason for me to want MongoDB, but not quite.  The real
reason is because I want the ability to eventually handle multiple
media types through MediaGoblin, and also allow for plugins, without
the rigidity of tables making that difficult.  In other words,
something like:

#+BEGIN_SRC javascript
{"title": "Me talking until you are bored",
 "description": "blah blah blah",
 "media_type": "audio",
 "media_data": {
     "length": "2:30",
     "codec": "OGG Vorbis"},
 "plugin_data": {
     "licensing": {
         "license": "http://creativecommons.org/licenses/by-sa/3.0/"}}}
#+END_SRC

Being able to just dump media-specific information in a media_data
hashtable is pretty great, and even better is having a plugin system
where you can just let plugins have their own entire key-value space
cleanly inside the document that doesn't interfere with anyone else's
stuff.  If we were to let plugins to deposit their own information
inside the database, either we'd let plugins create their own tables
which makes SQL migrations even harder than they already are, or we'd
probably end up creating a table with a column for key, a column for
value, and a column for type in one huge table called "plugin_data" or
something similar.  (Yo dawg, I heard you liked plugins, so I put a
database in your database so you can query while you query.)  Gross.

I also don't want things to be too lose so that we forget or lose the
structure of things, and that's one reason why I want to use MongoKit,
because we can cleanly define a much structure as we want and verify
that documents match that structure generally without adding too much
bloat or overhead (mongokit is a pretty lightweight wrapper and
doesn't inject extra mongokit-specific stuff into the database, which
is nice and nicer than many other ORMs in that way).

** Why wsgi minimalism / Why not Django

If you notice in the technology list above, I list a lot of components
that are very [[http://www.djangoproject.com/][Django-like]], but not actually Django components.  What
can I say, I really like a lot of the ideas in Django!  Which leads to
the question: why not just use Django?

While I really like Django's ideas and a lot of its components, I also
feel that most of the best ideas in Django I want have been
implemented as good or even better outside of Django.  I could just
use Django and replace the templating system with Jinja2, and the form
system with wtforms, and the database with MongoDB and MongoKit, but
at that point, how much of Django is really left?

I also am sometimes saddened and irritated by how coupled all of
Django's components are.  Loosely coupled yes, but still coupled.
WSGI has done a good job of providing a base layer for running
applications on and [[http://pythonpaste.org/webob/do-it-yourself.html][if you know how to do it yourself]] it's not hard or
many lines of code at all to bind them together without any framework
at all (not even say [[http://pylonshq.com/][Pylons]], [[http://docs.pylonsproject.org/projects/pyramid/dev/][Pyramid]], or [[http://flask.pocoo.org/][Flask]] which I think are still
great projects, especially for people who want this sort of thing but
have no idea how to get started).  And even at this already really
early stage of writing MediaGoblin, that glue work is mostly done.

Not to say I don't think Django isn't great for a lot of things.  For
a lot of stuff, it's still the best, but not for MediaGoblin, I think.

One thing that Django does super well though is documentation.  It
still has some faults, but even with those considered I can hardly
think of any other project in Python that has as nice of documentation
as Django.  It may be worth
[[http://pycon.blip.tv/file/4881071/][learning some lessons on documentation from Django]], on that note.

I'd really like to have a good, thorough hacking-howto and
deployment-howto, especially in the former making some notes on how to
make it easier for Django hackers to get started.