$ cat post/debugging-a-django-bug-that-brought-down-our-service.md

Debugging a Django Bug that Brought Down Our Service


March 6, 2006 was just another day when suddenly our service went down. It wasn’t a DDoS or some other external attack; it was an internal misstep. As the lead engineer for our platform, I found myself in the unenviable position of tracing back through code and logs to figure out what happened.

We were running a Django application with a PostgreSQL database backend on Ubuntu 6.10. The service had been stable, but today it just quit serving any requests. At first glance, everything seemed fine: no uptick in load, no obvious changes to configuration files or databases. But the logs showed one particular error repeated every few seconds:

File "/usr/local/lib/python2.4/site-packages/django/db/models/fields/__init__.py", line 308, in get_internal_type
    return self.__class__.__name__

It looked like some kind of weird recursion or deep import issue, but that didn’t make sense—Django is quite well-tested and maintained. I spent a few hours tracing through the code and log files, but nothing seemed amiss. The more I dug into it, the stranger the situation appeared.

Finally, in desperation, I decided to take the service down completely and start over from scratch. I wiped out the virtual environment and rebuilt everything from source. After an hour of meticulous setup, our service came back up without any issues. It was a relief, but only temporary. The problem had reappeared after about 20 minutes.

That’s when it hit me—maybe this wasn’t just about the code or configuration. Maybe I needed to look at how we were deploying and managing services in production. We were using Apache with mod_wsgi, which seemed straightforward enough. But as the service grew more complex, so did our dependency graph.

I started writing scripts to automate deployment, but they hadn’t been tested thoroughly under load. Each time a change was made, there would be a small window where things didn’t line up just right. And that’s exactly what happened today—something went wrong in one of these intermediate steps and brought down the whole stack.

This incident highlighted how fragile our setup was. I realized we needed to move towards more robust deployment strategies. We started using Capistrano for automated deployments, which helped us manage dependencies better and ensured each step was tested before moving on. It wasn’t perfect, but it was a step in the right direction.

The other lesson from this incident was about the importance of thorough testing. I had grown complacent over time, relying too heavily on the existing infrastructure without actively challenging its stability. This bug forced me to reassess our practices and workflows.

As the tech world moved rapidly towards open-source stacks like LAMP and Xen hypervisor, we were left behind a bit. Our stack was still largely based on Red Hat Enterprise Linux 4 and Python 2.4—pretty standard for the time but not cutting-edge by any means. I knew we needed to modernize our infrastructure, but it wasn’t just about keeping up with trends; it was about staying resilient.

Reflecting on this experience, I realized that as a team, we had been living in an echo chamber. We were so focused on delivering features and fixing bugs that we didn’t take the time to step back and reassess our underlying systems. This bug forced us to do just that.

In the end, while the immediate fix was to get the service running again, the long-term solution involved a lot of hard work: automating deployments, improving test coverage, and modernizing our infrastructure. But that’s what being an engineer is about—learning from mistakes and constantly striving for improvement.


This blog post captures the essence of dealing with a critical issue in a Django application during a time when open-source stacks were becoming more prevalent, and tools like Capistrano were starting to gain traction in the industry.