Plugin architecture for rails cms

Question

I'm working on a cms and wanted the ability to offer custom extentions for certain accounts. Like having a plugin with custom code that is only available or only used by that account. These custom extentions would be specific to the business needs of an account and perhaps unlikely that any other accounts would need it, but maybe. Is there a way that this could be done and to be loaded without having to restart the whole app, thereby creating downtime for the other accounts?

Answer 1

In terms of per-client plugin code, you could store the code in a data model and then eval() the code to dynamically execute it. (Of course you would want to do some serious sanity-checking / scrubbing on update to ensure the code does not contain malicious calls). Another approach could be to develop a custom tag library, much along the lines of what the Radiant CMS developers have built ... and then let your users "program" their behaviour using the tags provided. This gives you more control and better security at the expense of less flexibility.

In terms of the downtime question, if you are using a modern rails deployment approach I don't see how this should be an issue. The eval() approach above doesn't require a restart (unless your custom code calls "include ..." on libraries that are not installed at the time of the last boot - but getting these libraries installed is also an "out of band" problem that you would need to solve.

Passenger gives you the restart.txt file that you can touch to force a refresh. Similarly there are recipes for mongrel (like see saw) that allow you to progressively restart your mongrel stack to avoid downtime. I would pull these two issues apart mentally if I were you, as the dependencies between the two are not that great. Hope this helps.

Answer 2

I built a cms and added plugin support for it. Best thing you can do is have it be all database driven, the plugin exists for everyone, technically, but you can only make use of it if you've "purchased" it, or some other way of turning it on.. Which is really just a db record.

That'd be 0 downtime. :) Then again, I have no idea what the rest of your setup looks like. I'd think your solution is going to be pretty specifically tailored to your cms system design.