Wednesday, February 23, 2011

My rant about legacy code

"Ya ni llorar es bueno", this is a Mexican saying that translates to "it's not even worth crying anymore". I thought about this saying after a talked with few companies and friends regarding legacy application, specially legacy code that directly hit the ROI of the company. To add some context around this post, let me explain what does "legacy code" means to me:
  • It is using a technology relatively "old" (+5 years)
  • It is in production
  • The application plays an important role in the company

I have worked on a few of these applications and I hate most of them! Not because the they are hard but because of politics. It has been my perception that managers are "gun shy" when it comes to handle the re-write of legacy code when they are clearly out of control. I am not sure why this is, but this are some my reasons based on my interviews with tech leaders and developers:

  1. Time: aah, the Pandora box of managers. Lets face it, it is hard to estimate software projects, and worse the re-factoring of a major legacy code. The stakes are high if the re-factoring goes wrong. Managers have mentioned that these refactoring are a double edge sword because it can be really good, or it could eventually damage their reputation and the morale of the team.
  2. Resources: many manager are fighting with other departments when it comes on resources/programers. Many companies are trying to innovate and create new applications to latch on to the new business models. These projects take priority over the legacy systems that they have in place (if it's not broken, don't fix it).
  3. Domain experts: many of the large dev shops (+20 developers) have two types of development departments: engineer and support. The engineers are senior developers with at least 5 years of expertise. They develop the application based on the specs of the project manager and product owners. The support team are a mixture of junior and junior-senior developers. They take over the code when the engineers deploy the application to production. The problem with this model is the lack of mentoring/couching of the junior team. The support team does not have the know-how or the domain expertise as the engineers. The consequences are the introduction of bad code or bad practices when they need to add a feature or fix a bug.

Some of the dark side of the legacy codes are the following:
  • Bloated controllers and DAOs
  • Business logic is ALL over the code (DAO, stored procedures, controllers, DTO, the list goes on)
  • Silo effect - just a few developers know about the application
  • Fragile code - tightly coupled code
  • Bug identification and turn-around time is large
  • Application is slow

I doubt that I can get the right answer to this problems, but here is my advise to current and aspiring managers regarding this matter:
  1. Bite the bullet: if the legacy application is a major part of your business, don't wait any longer. Get a grip on this application before it get any worse and start doing a re-factoring by doing small iterations (not longer than 2 weeks old).
  2. Candid conversations: ask the tough questions regarding the application like "does the architecture needs to be changed?" Have all the developers review the current app and see what should be changed. Identify the large parts of the code to change (architecture) and what are the smaller (low hanging fruits) projects that can give more momentum to the project.
  3. Go agile! An agile methodology like XP, Scrum, and Kanban add great value to projects specially like pair programming, test-driven development (tdd), domain-driven development (ddd), and continuous integration (CI). The greatest thing about Agile is its rapid time to market. Small iterations means that your customers can see what you did in a couple of weeks and get their feedback. This also provides early risk reduction since you can find bugs relatively quickly. Pair programming helps mentor junior developers and avoid the silo effect. TDD guarantees that any code added to the application is tested before shipping it to production and gives better quality to your customers. DDD adds "depth" to your code and isolates all the business logic in one area of the code. This way, any developer know that if there is a change in the business logic, he/she needs to look for the domain packages. Finally, CI (building pipelines) it is primarily focused on asserting that the code compiles successfully and passes the suit of unit and acceptance tests (including performance and scalability tests).
Legacy code is a dreaded word for developers. The fact is that no developer wants to develop in Java 1.4 or Struts 1.x. If your want a company to attract good talented individuals, try to handle your legacy code.

Again, I'm sure that I missed or don't understand ALL the reasons why so many companies have large legacy code in their core systems, so please...I welcome your thoughts in this matter.


  1. Bravo Marcelo! It seems like there is a huge gap between managers and developers. I have seen so many unmaintainable slow bug infested bad coded applications using the outdated waterfall methodologies... If John Lennon was alive and he was a programmer, he would write Imagine using TDD, CI, static code analysis, JUnit, code coverage, agile, XP instead of PEACE, HEAVEN and et cetera.

  2. Edson, you are hilarious! Thanks!!