Monday, August 27, 2018

Configuration as a Point of Failure

Recently, I happened to restore service for our /giphy Slack command.  I originally had things set up poorly, so we needed a ProxyPass configured in every virtual host that wanted to run PHP.  That changed at some point.

I updated all of the configurations in git, of course.

But our giphy endpoint is a separate project, meant to be shared with the world, which therefore doesn’t follow our standard layout.  Its config is not in its git dir; I missed it in the update pass.

I had also just dealt with all the config file merging and changes in the Ubuntu 18.04.1 LTS update.

It really got me to thinking: anything configurable is a point of failure. Whether it’s a process/knowledge failure like with our giphy endpoint, or merge conflicts in *.lock or webpack.config.js files, or a system package changing its configuration semantics or defaults between versions:

The presence of configuration allows broken configurations.

We should try to avoid unnecessary configurability in a system.  This is also very difficult to achieve—a system that only has defaults absolutely needs to have correct, working defaults.  The problem only gets harder in open source, where a project often serves many diverse users.

Also, one of my greatest weaknesses is throwing in easy-to-build options “just in case.”

Finally, it’s bad practice to bake credentials into a git repository, but how shall they be provided without configuration?  EC2 has IAM Roles, but they don’t work in VirtualBox… it really does seem like some configuration is a necessary evil.

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