Adventures in Technical Debt

| posted in: technical debt  refactoring 

Almost five years ago the University where I work suffered a fire in the main library building on campus. This building also houses, in the basement, the (then) primary data center. Two holes in the ceiling of the data center, which had been made to allow conduit runs, had not been properly sealed. We had a major water intrusion.

In the months that followed, as we worked to restore services and find ways to move out of the now compromised data center, we used VMware Cloud on AWS. Most of our production servers were virtual machines running in vSphere in our vBlock. With VMC we could “lift and shift” workloads from on-premises to AWS relatively quickly.

This spring we are working to upgrade all our Ubuntu servers to version 22.04. This required some adjustments to our mod_cluster configuration and our Apache configuration. Fortunately we have a test environment and an infrastructure automation tool to help make test and prod the same.

Our infrastructure automation tool is Chef. One of the features of Chef is the ability to “pin” the version of resources through the environment. All the nodes (Chef parlance for server) exist within an environment, with clever names like “test”, or “prod”. When we set out to migrate to VMC a new environment was created, called “prodvmc”. Catchy.

At about the same time, some version pinning occurred in the “prod” environment. Pinning that was never revisited. Pinning that was committed to the repository with no meaningful comments as to why the versions were pinned.

All of our Ubuntu 22 testing occurred, naturally enough, in the “test” environment. We never exercised the pinned versions. Also, apparently to reduce setup time in Vagrant, some resource definitions had code that said, “don’t do this if the environment is ’test’”.

Both of these decisions have produced some technical debt we now have to pay. The infrastructure automation code that is stepped around for the test environment hasn’t proved to be hard to overcome. Frustrating perhaps, but not insurmountable.

Unwinding the version pinning is a much larger debt. Our applications are Java-based web applications running in Wildfly application server. One of the resources that was pinned is the primary definition for our Wildfly clusters. A definition used by all of our major applications.

Not all of the servers belong to the “prod” environment. Slightly more than half belong to the “prodvmc” environment, where there was no pinning. For the rest, we now need to revisit four years of commits to determine what will happen to these production resources, when we remove the pinning constraint and update to the latest version of the infrastructure definition.

One measurement of an organization’s maturity, is how well things are documented. In our haste to move to VMC we made a decision to pin some versions, most likely thinking, “This is temporary for reason “x”, we’ll come back and address this once the move is completed.” And then we never went back. Not going back apparently hasn’t had too large an impact since all our applications are working. But not documenting the reason for the decision is going to cost us some time.

Lessons to learn:

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Mark H. Nichols

I am a husband, cellist, code prole, nerd, technologist, and all around good guy living and working in fly-over country. You should follow me on Twitter.