How should you track technical debt?
If you work on a commercially successful project, the chances are you've experienced the pain of technical debt. As a codebase grows larger and larger, inevitably you find that some of the choices made in the past are resulting in a slowdown in productivity.
It's a problem I've given a lot of thought to over the years. I created Pluralsight course on "Understanding and Eliminating Technical Debt" and often speak about it. In fact I'll be doing so again next month at Technorama Netherlands (would be great to see you there if you can make it!)
Tracking technical debt
One of my recommendations is that technical debt should be tracked. In my Pluralsight course, I suggested creating a "technical debt document". In this document, you list specific issues that need addressing, explain what problems they are currently causing, and what the proposed solution is. Other useful information includes estimating how long a fix would take, and identifying upcoming features in the roadmap that will become easier to implement once this technical debt item has been resolved.
Technical debt can come in many forms. I often break it down into categories like "Code debt", "Architectural debt", "Technological debt", "Test debt" etc, but the common theme is that there is something less than ideal about the code or tooling that needs to be addressed. By tracking these issues somewhere, you can prioritize and plan to address them.
Book recommendation: "Managing Technical Debt"
I recently discovered a great new book, Managing Technical Debt, written by Philippe Kruchten, Robert Nord and Ipek Ozkaya. The authors have researched technical debt at an academic level, (there is even a conference about technical debt now!) and so I was very eager to read what they had to say to pick up any new ideas.
It's a great read, and written at a level that you could share it with both developers and managers alike. It's practical and pragmatic, and it was nice to see that they share a very similar understanding and approach to technical debt to the one I take in my Pluralsight course.
But there were several new insights, and the one I want to highlight in this post is what the best way to store "technical debt items" (as they call them) is.
Technical debt register
In the book, the authors recommend having a "technical debt register". It's similar to my document idea, but they recommend using your regular work tracking tools to store the "technical debt items". In other words, wherever you record your defects or backlog of new features (e.g. GitHub issues, Jira, Azure DevOps), should also be where you store technical debt items.
I recommend including debt actions (stories) in the same tracking tool as all other work and as part of a single program or team backlog. Our agile-inspired phrasing is "all work is work; all work goes on the backlog" Kruchten, Nord & Ozkaya, Managing Technical Debt
The reasoning for this is simple. Technical debt, just like defects and features, represents work that needs to be done. So it needs to be visible and able to be planned in. You could either create a new entity to represent a technical debt item, or just tag items with "TechDebt" to differentiate them.
This idea is one I had initially considered but rejected because I feared that it could be abused. What if the technical debt register filled up with thousands of "leftover" tasks that were in reality never going to get actioned? A kind of way to assuage our guilt that we didn't really finish our work. "Didn't get round to writing any unit tests? Don't worry! Just add it to the technical debt register!"
However, having read the book, I think I'm coming round to their way of thinking. I can see a number of benefits over using a document for tracking technical debt items:
- they can be planned and estimated with the same tooling used for defects and features
- you can associate commits to technical debt items
- technical debt items can also be linked to featured and defects
- they support discussion (not everyone will agree on the best way to address these issues)
- they are easily added by anyone on the team (don't need to know where to find the document, or wait to check it out)
Two levels of technical debt items
The authors suggest that there are two levels of technical debt item: (1) simple, localized code-level debt and (2) wide-ranging, structural, architectural debt.
The simple items relate to a specific area of code and might take a day or so to address. A team could allocate a certain percentage of time each iteration to resolving these technical debt items.
Examples of wide-ranging items might be wanting to move from a monolith to microservices, or switching from server side rendering to a SPA framework. These are not necessarily achievable in one step, and need to be broken down into smaller chunks. In some cases, dedicating an entire iteration to working on one of these technical debt items might be warranted.
Automating creation of technical debt items
Another interesting idea is whether static code analysis tools could generate technical debt items. Personally, my fear here is that there would simply be too many of these, and many static code analysis tools generate high numbers of "false positives".
So personally although I find a lot of value in static code analysis tools, I wouldn't want to automatically convert each item discovered into a technical debt item. My preference is to use code analysis tools that give you immediate feedback as you are coding (this is one of the great strengths of ReSharper) as the most efficient time to address problems with code is while you are still working on it.
If a static analysis tool does highlight some particular areas of concern in the codebase, then you could always manually create an entry in the technical debt register that groups related instances together into a single item, rather than creating one entry per offending line of code.
Another good suggestion was to standardize on a way of marking technical debt issues in code. Many developers include comments like "TODO" or "FIXME", as a way to highlight improvements that are desirable in the future, but for whatever reason could not be done at the time. By adopting a standard, it's easy to find those items and generate technical debt items as necessary in the technical debt register.
Prioritizing technical debt items
Let's suppose we follow this guideline and create a technical debt register. Now we've got hundreds of items, big and small, each detailing a way in which our code should be improved to make our lives easier going forward. But how do we prioritise them?
Well, I would not recommend simply randomly picking off technical debt items to solve. Technical debt items are only potential problems - they're not actually causing any harm unless you are working on a specific part of your system.
So it's really important that your technical debt items are associated with a specific area of code. That way, when you are about to embark on new work in that area of code, you can review the technical debt register to see what known issues might get in your way. This means you can strategically address the ones that will most benefit upcoming work.
"Before starting a new feature or story, check the backlog to identify any known debt items that should be considered during implementation because they impact the same area of the code or would otherwise impede its development" (Kruchten, Nord & Ozkaya, Managing Technical Debt)
Numbers don't matter
It's also important to point out that it really doesn't matter if the number of technical debt items grows very large. Remember they are only potential issues, not actual problems, and it's totally fine if many of them are never addressed.
Of course, you might want to eventually prune some that have sat dormant for several years, or that have been obsoleted by other advances in the code. But they're not like defects. With defects, we typically want to get to a count of zero. Technical debt items are more akin to cool ideas for future features: they're not all going to get done - only the ones that bring real value.
I highly recommend having at least some way to track outstanding technical debt items for your projects, and reading the Managing Technical Debt book has convinced me to give tracking them in the standard project management tools a go. So I'm planning to migrate the issues listed in my existing technical debt document into our regular working tool and see if that helps us more effectively plan and prioritise which technical debt items should be addressed next.
I saw a very interesting presentation by Steve Freeman that included the shape of the TD curve (impact over time as TD accrues). He demonstrated that the curve is not as simple as one might expect, and that there's a point of inflection where the impact of TD suddenly runs away out of control. Alarming. This insight comes partly from his analogy of TD as "unhedged Call Options", well worth catching up on.Will Hiorns
thanks, sounds interesting. And yes, I'm pretty sure there is an inflection point where the problem has got out of control, and it can be reached surprisingly quickly, maybe only a couple of years into a projectMark Heath