Month: June 2019

Elegance: UI vs implementation

If you ask the question, “What is a Docker container?”, it turns out that the Linux operating system doesn’t actually have a notion of a container at all. Instead, a Docker container refers to a cobbled together set of Linux technologies, such as cgroups, network namespaces, and union filesystems. However, from the point of view of the end-user, a container is very much a real thing. In particular, it exposes to the user images as an entity, and a command-line tool for pulling down images from a repository and running them.

The Docker container implementation may be built (in the Unix tradition!) with duct table and baling wire, but the user interface is elegant. It’s easy for a new user to get started with Docker once they’ve installed it. Bryan Cantrill points out that the advantage of Docker over container technologies developed in the BSD world is Docker’s notion of images as effectively static binaries that allow developers to think operationally and move faster.

Contrast that with git. The implementation is quite elegant: git represents the data under version control as a hash tree, with pointers into nodes in the tree. Git commands are tree manipulations: adding leaf nodes, moving branches from one part of the tree to another, smooshing nodes together, and so on. (I used Subversion for years and had no idea what was going on under the hood).

On the other hand, the command-line interface that git exposes is a nightmare. It’s so hard to use that trying to build a more usable command-line interface is a full-blown academic research project.

The elegance of a user interface and the elegance of an implementation are orthogonal. One doesn’t necessarily lead to the other.

Postmodern engineering

When I was younger, I wanted to be a physicist. I ended up majoring in computer engineering, because I also wanted gainful employment, but my heart was always in physics, and computer engineering seemed like a good compromise between my love of physics and early interest in computers.

I didn’t think too deeply about the philosophy of science back then, but my beliefs were in line with the school of positivism. I believed there was a single underlying reality , the nature of this reality was potentially knowable, and science was an effective tool for understanding that reality. I was vaguely aware of the postmodernist movement, but mostly by reading about the Sokal hoax, where the physicist Alan Sokal had demonstrated that postmodernism was nonsense.

Around the same time, I also read To Engineer is Human: the Role of Failure in Successful Design by the civil engineering researcher Henry Petroski. The book is a case study on how civil engineering advanced through understanding structural failures. Success, on the other hand, teaches the engineer nothing.

Many years later, I find myself operationally a postmodernist (although constructivist might be a more accurate term). When I study how incidents happen, I no longer believe that there is a single, underlying reality of what really happened that we can access. Instead, I believe that the best we can do is construct narratives based on the perspectives of the different people that were involved in the incident. These narratives will inevitably be partial, and some of them may conflict. And there are things that we will never really know or understand. In addition, contra Petroski, I also believe that we can learn from studying successes as well as from studying failure.

I suspect that most engineers are steeped in the positivist tradition of thinking as well. This change in perspective is a big one: I’m not even sure how my own thinking evolved over time, and so I don’t know how to encourage this shift in others. But I do believe that if we want to learn as much as we can from incidents, we need to work on changing how our fellow engineers think about what is knowable. And that’s a tall order.