Dec 032010

Over the past 6 months or so I’ve been spearheading the re-write of RPI’s Shuttle Tracking system into something less RPI-specific to make it useful to other organizations.  Part of this has been small semantic changes like removing RPI-specific words, location references (like the hard coded map center) and CAS-based authentication, but on a much larger level the application was restructured to do a lot more.

Both old and new systems store the same data (vehicles, vehicle positions, routes, and stops along the routes) but you no longer have to directly manipulate the database to hide a stop from the map and you don’t have to understand how to build a KML file to change the route around anymore.  Additionally, the new system feel much less “hacky” if that makes any sense, things are where they should be (for the most part) and there’s actually some back end pages worth showing off; we’ll be able to iterate and release new features much faster.

I am always impressed when an interface get’s polished, but I’m rarely the one to do it (Thanks Reilly!)… what I can take credit for is the switch to Ruby on Rails 3.  Flagship Geo was a primary driver behind this, Rails 3 was necessary to pull in all those resources like the route and stop editors, but Rails 3 should also provide some performance enhancements.

The server has also been upgraded to include Ruby 1.9.2 via RVM because I think that makes it harder to break things.  When the site goes into production we’ll be serving using Passenger 3 to, in theory, speed up our web server end of the pipe.

As for the timeline of this release, the current system is staging in beta at RPI for performance testing / feedback.  After I’m satisfied the new one is performing at least as well as the old one it will be switched into production.  In the meantime, you can follow development on github:

Jul 022009

I finished transitioning the thumbnail generation to a background process, using the same approach I use for video conversion because it seems like a thumbnail is just a special conversion. You can check out the commit here if you’re interested.

Adding another BackgroundRB worker was easy to do, but I’m finding that its wreaking havoc on my server. The box I’m developing bonsai video on is a pretty lightweight box (it might be my lightest now that I think about it). I choose to do this to force me to make sure my code would work well on slower boxes. So far I haven’t had any major issues. FFMPEG seems to convert videos fairly quickly, and up until today everything seemed under control. Combined, the 3 BackgroundRB workers are using up somewhere between 25 – 40% of my system’s memory, as reported by top. I’m not sure why the processes are using so much when they are sitting their waiting for work, and I doubt the sql overhead of pooling for new jobs (I use the persistent job queue) is that overwhelming.

This has made regular site navigation terribly slow, but at least pages don’t time out like they previously did when generating thumbnails. I think I have 3 options to fix things:

  1. Refactor and combine the workers, so both videos and thumbnails are handled by the same worker. I suspect this might be able to save me 10-15% on my memory usage, but its not as clean as I’d like it to be.
  2. Replace BackgroundRB with something else that may be a bit faster or more efficient. It looks like people have experienced the same problems I’ve had, maybe just on a smaller scale since they have more powerful servers. I would rather avoid this approach, since it means more development time reworking things I’ve already done.
  3. Buy more RAM or upgrade the server. This one is tough for me, as I’d like this to be able to run on a fairly low-end machine, but I’ve found that Ruby on Rails has higher system requirements than something like PHP would. Additionally, this costs money.

For now, I’m just going to turn off the background workers so I can do some interface work.