软件的寿命：你希望多久能从头开始？[英] Lifespan of Software: How often do you expect to do start from scratch?

问题描述

I've heard people say that the average lifespan of software is about 3 years, but that seems shockingly low to me. I don't buy it.

After all, some of my clients have lumbering mainframes that have been around for 20 years, and they're so entrenched that they might live forever.

I personally tend to start talking about severe refactoring when the platform gets so old that it's bad for our skills (we are contractors) and otherwise inefficient to keep maintaining the project. I'm thinking about ASP Classic here. That can be a 5 to 8 year window, and it doesn't even need to be a rewrite.

Of course, I have also seen projects that incurred a lot of technical debt because someone caved to stakeholders too often or a dev didn't know how to plan for change. Or the project was started on a weak platform that didn't scale well. That radically reduces the lifespan.

Maybe those projects are the ones that tend to live 3 years. Or less.

One last thought: Some studies have proven that it's cheaper to maintain old code than to write new, and I believe it. Rewriting large systems is always way harder and more expensive than it looks.

Does all of this conspire to indicate that developers tend to re-write too early, and perhaps naively? I'm thinking yes, and I can see how that's an easy mistake to make.

What are your experiences here?

推荐答案

The team that I'm working on has been developing the same web application for 6 years, and there's no end in sight. In that time, it's gone from Classic ASP to ASP.NET 1.1 to ASP.NET 2.0, so various modules have undergone incremental rewrites, but never anything like a from-scratch rewrite. Every so often somebody will say how nice it would be if we could start over, but we have 60,000+ users: there's no way they're going to wait the 12 to 18 months it would take while their updated functionality or features sit on a shelf.

I've only had the chance to do a ground-up rewrite twice. In both cases, the reason we had time and buy-in to do so was because we had a rather small group of customers using an already stable version. When we went to them with the new product, they all agreed that it was better than the old system, but very few of them bought it because they were already happy with what they had. It was a lot of fun for the programmers, but ultimately it was a loss for the business.

So, from personal experience, the things that you get to start from scratch every 3 years are likely not used by many people. When you've got a widely used application or service, especially in a corporate environment, it's hard enough to get buy-in to do gradual upgrades, let alone rewrites.