Hi
Its final evaluation period, so I take this time to write some final notes
on the project I worked on this summer, that is integrating collaborative
editing into the VisualEditor project[1]. So to fit rightly into the scope
of GSoC, the whole collaborative thing on VisualEditor was split into two
phases, of which, the first phase was aimed to be delivered. The system is
to allow only one user to make changes to a document in an editing session,
while the others can spectate the changes in realtime, therefore halting at
a stage where concurrency issues arising from multiple editors, would be
deal with.
The project is majorly composed of the server-side and client-side
components. A server(collaboration server in this context) has been built,
which co-ordinates different clients participating in an editing session.
Some of the things that the collaboration server does are -
1. Maintains a centralized copy(server's copy) of the document that is
worked on in an editing session.
2. Listens to the incoming transactions from a client who makes a new
change to the document and applies those transactions to the server's copy
of the document.
3. Broadcasts an incoming transaction to the other clients subscribed to
the same editing session that triggered the transaction, so that they can
apply that transaction to their local documents and keep in sync.
4. Re-use the VisualEditor modules to create a binding for taking care of
the above.
5. Talks to an external parsoid service, when it needs the HTML feeding for
initializing a document. Initially it used parsoid modules to parse wiki
content internally, but considering the scalability, this is done over HTTP
using an external parsoid service.
6. And ofcourse, it scales the above features for multiple editing sessions.
The server is built in node.js and uses socket.io library for making
persistent connections with the clients. For testing, nodeunit has been
used.
The other major aspect of the project is, the client module, which hooks
into VisualEditor, initiates a connection with the server, and does all the
things with transactions including translating them to the server. The
components of client module, like other components of VE, interact using
events, which has allowed me to test them easily. And, for testing some
major parts of the code, qunit has been used.
So the above, makes for more than 90% of all that I wanted to do. Some of
the things that remain are -
1. Authentication of users on collaboration server - Currently, the users
which connect to the collaboration server are not validated before putting
them on one of the editing sessions. To overcome this, there has to be way
by which MediaWiki could help in validating a user coupled with some extra
information by a third party. This called for the need of OAuth, but since
OAuth isn't ready yet, Roan and Trevor suggested to have a new API module
for doing that. I've implemented the API module[2], and written the
authentication part in my project aligned with the implementation. So its
nearly done.
2. Transfer of editing control - This is one feature I've not worked on due
to confusions mainly related to correctly attributing edit credits to
particular users which took part in the editing session. I think, this
should not be hard to implement, once the confusions are stripped away.
The above are part of the tasks in my current plan. My plan for future is
to further refine the code that I've written so far, especially the server
side code. There have been umpteen times when I've shown my demo to people,
and they've said, 'dude, it would be amazing if it supported multiple
editors', that has always enticed me to work on supporting multiple
editors. But, I realized, it was really good decision to cut the scope till
what has been done for the sake of robustness. Although, it will be a
challenging task, but its definitely in my plan to work on supporting
multiple editors in future. The time when we won't need Etherpad, hopefully
:)
It has been a great fun and learning time working along side some bright
students, dedicated volunteers and amazing Wikimedia engineers, especially
the VisualEditor team. Special thanks to Trevor, Gabriel, Roan,
Mark(traceur), and all those who ever showed interest in my project.
Definitely looking forward to more awesome work.
Cheers!
--
Ashish Dubey