[RFC/Summit] `npm install mediawiki-express` - Wikitech-l

5 Nov 2015

Architecturally it may be desirable to factor our codebase into multiple
independent services with clear APIs, but small wikis would clearly like a
"single server" installation with all of the services running under one
roof, as it were. Some options previously proposed have involved VM
containers that bundle PHP, Node, MediaWiki and all required services into
a preconfigured full system image. (T87774
<https://phabricator.wikimedia.org/T87774>)

This summit topic/RFC proposes an alternative: tightly integrating PHP/HHVM
with a persistent server process running under node.js. The central service
bundles together multiple independent services, written in either PHP or
JavaScript, and coordinates their configurations. Running a
wiki-with-services can be done on a shared node.js host like Heroku.

This is not intended as a production configuration for large wikis -- in
those cases having separate server farms for PHP, PHP services, and
JavaScript services is best: that independence is indeed the reason why
refactoring into services is desirable. But integrating the services into a
single process allows for hassle-free configuration and maintenance of
small wikis.

A proof-of-concept has been built. The node package php-embed
<https://www.npmjs.com/package/php-embed> embeds PHP 5.6.14 into a node.js
(>= 2.4.0) process, with bidirectional property and method access between
PHP and node. The package mediawiki-express
<https://www.npmjs.com/package/mediawiki-express> uses this to embed
MediaWiki into an express.js <http://expressjs.com/> HTTP server. (Other
HTTP server frameworks could equally well be used.)  A hook in the `
LocalSettings.php` allows you to configure the mediawiki instance in
JavaScript.

A bit of further hacking would allow you to fully configure the MediaWiki
instance (in either PHP or JavaScript) and to dispatch to Parsoid (running
in the same process).

*SUMMIT GOALS / FOR DISCUSSION*

   - Determine whether this technology (or something similar) might be an
   acceptable alternative for small sites which are currently using shared
   hosting.  See T113210 <https://phabricator.wikimedia.org/T113210> for
   related discussion.
   - Identify and address technical roadblocks to deploying modular
   single-server wikis (see below).
   - Discuss methods for deploying complex wikitext extensions.  For
   example, the WikiHiero
   <https://www.mediawiki.org/wiki/Extension:WikiHiero> extension would
   ideally be distributed with (a) PHP code hooking mediawiki core, (b)
   client-side JavaScript extending Visual Editor, and (c) server-side
   JavaScript extending Parsoid.  Can these be distributed as a single
   integrated bundle?

*TECHNICAL CHALLENGES*

   - Certain pieces of our code are hardwired to specific directories
   underneath mediawiki-core code.  This complicates efforts to run mediawiki
   from a "clean tree", and to distribute piece of mediawiki separately.  In
   particular:
   - It would be better if the `vendor` directory could (optionally) live
      outside the core mediawiki tree, so it could be distributed
separately from
      the main codebase, and allow for alternative package structures.
      - Extensions and skins would benefit from allowing a "path-like" list
      of directories, rather than a single location underneath the
core mediawiki
      tree.  Extensions/skins could be distributed as separate packages, with a
      simple hook to add their locations to the search path.
      - Tim Starling has suggested that when running in single-server mode,
   some internal APIs (for example, between mediawiki and Parsoid) would be
   better exposed as unix sockets on the filesystem, rather than as internet
   domain sockets bound to localhost.  For one, this would be more "secure by
   default" and avoid inadvertent exposure of internal service APIs.
   - It would be best to define a standardized mechanism for "services" to
   declare themselves & be connected & configured.  This may mean standard ro
   utes on a single-server install (`/w` and `/wiki` for core, `/parsoid`
   for parsoid, `/thumb` for the thumbnailer service, etc), standard ports
   for each service (with their own http servers), or else standard locations
   for unix sockets.
   - Can we leverage some of the various efforts to bridge composer and npm
   (for example <https://github.com/eloquent/composer-npm-bridge>), so we
   don't end up with incompatible packaging?

Phabricator ticket: https://phabricator.wikimedia.org/T114457

Download the code for mediawiki-express and play with it a bit and let's
discuss!
 --scott

-- 
(http://cscott.net)