Al Hoang

Software Maniacs has a great blog post explaining what went wrong with one of their Django deployments. In the end it wasn’t exactly Django but a mix of how a particular table for the backend database (MySQL) was being abused by the web application (the sessions table. Here’s a snippet:

In general Django’s sessions are made smart enough — while stored in a DB they don’t touch it at all if your application doesn’t write anything in them. Unfortunately we used them in an interesting manner.

• Read it yourself
• Kudos to High Scalability

So I decided to take a peak at the up and coming web framework for Haskell called HApps however the web site seems down.

Normally, I wouldn’t care too much downtime however they have been down for OVER a day and a half from the time of this post. I find it hard to take the high availability aspect of HApps seriously when they can’t be a little more serious about trying to keep up their main site. It seems they’re ‘looking into it’ but some update like ‘we forgot to pay our DNS bill’ or ‘our provider just screwed us over and this might take awhile’ would be nice…

Ah well… I guess I’ll check in a week or two.

Your toilet has just subscribed to the digital life…

Look at it here

On my workstation at work I’ve been running Ubuntu 8.04 to test out something I’ll post on later. However, one thing that was driving me nuts was that tidy was blowing up with a very unhelpful message like so:

/usr/lib/ruby/1.8/tidy/tidybuf.rb:39: [BUG] Segmentation fault

At first I thought it was some incompatibility with the gem installed version of tidy however after a bit more searching it seems tied with a specific bug in Debian that is logged here. Basically, the recent version of libtidy has some sort of instability that will blow up on certain types of HTML input. Kind of not useful I say…

Looks like this has been fixed in Debian unstable so this might be a perfect candidate to have merged into Ubuntu since this really sucks inheriting a package bug.

Read the Bug Report

One of the problems with DIY PC builder-types is the joy of finding out the pieces that you try to assemble together have incompatibilities with each other. Sometimes it affects you at the hardware level, the OS level, or the application level. Either way it’s always a time sink isolating the exact problem.

One unpleasant surprise I found out is that the QBic E3901 SFF PC would not recognize a Hitachi T7k500 250GB HDDs when I plugged it in and powered it up. Some things I knew it wasn’t:

• Dead Hard drive – No, I just pulled it from another machine
• Bad cable – No, I just tested this cable on another HDD that DID work in this machine
• Bad power cable – See Bad cable

After some more snooping around I found a useful answer on the Gigabyte website for the southbridge chipset that the Qbic E390 uses. Basically, the VIA VT8237/VT8237R-based southbridges cannot support hard drives SATA HDDs that run at 3.0Gb/s speeds it seems. The only workaround is to see if the HDD can support changing the interface speed. Unfortunately, the Hitachi does not…

I was able to test with another HDD that allowed setting the speed down to 1.5Gb/s and that came up perfectly after I downclocked the interface speed. If I tried to set the speed to 3.0Gb/s it was completely ignored by the BIOS.

Anyways, it seems sticking with PATA will be a safer bet for the QBic’s or make sure the HDD supports the lower transfer speed as well….

One of the Flickr engineers was nice enough to blog about their general process for adding capacity to their database backend. Seems the process went from a straight 20-hour table alter process to a more staggered but sleep fulfilling approach.

The newer approach does seem to require having a certain set of extra capacity to handle taking some machines offline and performing a pretty long offline operation while still continuing to run.

Read it yourself

DistroWatch has a very good article summarizing the state of running OpenSolaris on the desktop at the moment. Personally, I’m interested in Solaris technology seeing more widespread usage although am not a gigantic follower at the moment.

For me the most interesting part was their discussion on what is happening with Nexenta, a project to graft the power of the Debian/Ubuntu userland on an OpenSolaris foundation. To me this seemed like one of the more promising projects since the mental overhead of relearning a whole bunch of new commands drops by a large factor and I can focus on really grokking the parts that make Solaris unique and not get too involved in the other parts until I feel good and ready to dive in.

Currently, Nexenta has decided to step away from the desktop and focus on the server backend which I think is just dandy since most of the features that OpenSolaris touts are more appropriate for the server at the current moment. (ZFS, Zones, Xen) and I think it’s worth getting these tools integrated in seamlessly without too much fuss.

Currently, one of the annoying things that I had learned when trying to play with OpenSolaris is that some features that get a bit of press require following bleeding edge of OpenSolaris which requires learning to keep track of basically trunk for a distribution. (For example trying to play with Xen is something that requires more recent builds of Open Solaris). While there is something to be said for learning things from following trunk. It can be a little frustrating when you also want your computer to actually do some work outside of sending bug reports and searching forums / mailing lists / blogs for ‘How do I get X working’

The Gentoo Wiki to the rescue again. I’m sure you can find lots of other examples as well if you Google around.

I was experimenting with trying to play videos in the desktop background so I can work on other things while passively watching videos that I really didn’t want to spend 100% of my concentration on. However when I tried to use mplayers -rootwin option under Ubuntu it did not show anything.

After doing some Googling around, it seems that the problem is tied with how rich desktop environments like KDE and Gnome manage the ‘desktop’. They normally override the traditional X11 root window with their own which means that sending output to rootwin won’t show anything.

However, luckily there are ways around this. One post on the mplayer list mentioned ways to disable background handling by GNOME and KDE. However I could not get this working under Gnome. After some more Googling around I found that Lifehacker had a hint on how to enable screensavers in the background. So using that information it was rather simple. The recipe for Ubuntu is:

# Tell GNOME to not handle the desktop
$ gconftool-2 –type bool –set /apps/nautilus/preferences/show_desktop false
# Play a video file in the rootwin as fullscreen
$ mplayer -rootwin -fs my_cool_video.avi

One of the joys of living on the edge of Linux releases is the fun of dependency hell. At present, vmware server does not run on the latest released kernel 2.6.24. Which means if you NEED vmware server, you’re screwed. At least until the folks at vmware update vmware server to work with the latest kernel release.

• An Ubuntu Forum on the problem
• A vmware.com forum with more details

I just noticed that The Ruby Programming Language Book by David Flanagan is out on Safari now. This looks like an update to Ruby in a Nutshell which has been a rather disappointing title for me personally.

After a glance through the contents of this updated edition it looks like this one could be a real winner on hand for Ruby programmers wanting a organized and clean description of some of the deeper parts of Ruby without having to trawl through piles of blog posts or read through piles of source code just to get an explanation. While there is much to be said from learning through reading source code. Good explanations of concepts and code are something to be valued. Let’s hope this title really is what I think it is. Either way, I can’t possibly make a thorough judgement call on a book I’ve not really read through. So take my thoughts on the book with a grain of salt. I only spent 20 minutes glancing through the contents and skimming some sections to see if it had the type of content I would be interested in.

On a side note it seems that the author rebukes a blogger denigrating the book before it’s even out yet. He also brings up the Ruby Fanboy / Club phenomenon that supposedly has been on the rise in the Ruby community. I guess popularity brings the ‘Club’ in no matter how hard you try to fend it off.

Avery Pennaru posted a blog entry on git is the next UNIX where he hypothesizes that:

git is a totally new way to operate on data… Git was originally not a version control system; it was designed to be the infrastructure so that someone else could build one on top… Git is a platform… Much like Unix itself, git’s actual software doesn’t matter; it’s the file format, the concepts, that change everything.

So the underlying ideas are what makes git very powerful. Interesting thoughts. I’ve played around with using git but I still can’t see it past a version control system at the moment. A VCS that still has very weak Windows support which is a serious problem for getting a TEAM of people to actually use the system. But I see that Windows support slowly moves forward.

Anyways, I want to believe the hype in git but show me some real-world examples instead of pie in the sky thoughts, please?