A Tale of Software Rewrites

What follows below is an excerpt from Michael Feathers’ book Working Effectively with Legacy Code. You can find it in Chapter 24, “We feel overwhelmed. It isn’t going to get any better.” In fact, I was sure this was a stand-alone essay, in the likes of those by Paul Graham, but it was nowhere to be found online. It is just too good to pass up, so I shamelessly reproduce it here.

Considering that most of us are stuck maintaining legacy code, most of the time, there is educational insight there for everyone.

~

Often people who spend time working on legacy systems wish they could work on green-field systems. It’s fun to build systems from scratch, but frankly, green-field systems have their own set of problems. Over and over again, I’ve seen the following scenario play out:

An existing system becomes murky and hard to change over time. People in the organization get frustrated with how long it takes to make changes in it. They move their best people (and sometimes their trouble-makers!) onto a new team that is charged with the task of “creating the replacement system with a better architecture.”

In the beginning, everything is fine. They know what the problems were with the old architecture, and they spend some time coming up with a new design. In the meantime, the rest of the developers are working on the old system. The system is in service, so they receive requests for bug fixes and occasionally new features.

The business looks soberly at each new feature and decides whether it needs to be in the old system or whether the client can wait for the new system. In many cases, the client can’t wait, so the change goes in both. The green-field team has to do double-duty, trying to replace a system that is constantly changing.

As the months go by it becomes clearer that they are not going to be able to replace the old system, the system you’re maintaining. The pressure increases. They work days, nights, and week-ends. In many cases, the rest of the organization discovers that the work you are doing is critical and that you are tending the investment that everyone will have to reply on in the future.

The grass isn’t really much greener in the green-field development.

~