Slashdot Mirror
Lessons From Six Software Rewrite Stories (medium.com)
A new take on the age-old question: Should you rewrite your application from scratch, or is that "the single worst strategic mistake that any software company can make"? Turns out there are more than two options for dealing with a mature codebase. Herb Caudill: Almost two decades ago, Joel Spolsky excoriated Netscape for rewriting their codebase in his landmark essay Things You Should Never Do . He concluded that a functioning application should never, ever be rewritten from the ground up. His argument turned on two points: The crufty-looking parts of the application's codebase often embed hard-earned knowledge about corner cases and weird bugs. A rewrite is a lengthy undertaking that keeps you from improving on your existing product, during which time the competition is gaining on you.
For many, Joel's conclusion became an article of faith; I know it had a big effect on my thinking at the time. In the following years, I read a few contrarian takes arguing that, under certain circumstances, it made a lot of sense to rewrite from scratch. For example: Sometimes the legacy codebase really is messed up beyond repair, such that even simple changes require a cascade of changes to other parts of the code. The original technology choices might be preventing you from making necessary improvements. Or, the original technology might be obsolete, making it hard (or expensive) to recruit quality developers.
The correct answer, of course, is that it depends a lot on the circumstances. Yes, sometimes it makes more sense to gradually refactor your legacy code. And yes, sometimes it makes sense to throw it all out and start over. But those aren't the only choices. Let's take a quick look at six stories, and see what lessons we can draw.
For many, Joel's conclusion became an article of faith; I know it had a big effect on my thinking at the time. In the following years, I read a few contrarian takes arguing that, under certain circumstances, it made a lot of sense to rewrite from scratch. For example: Sometimes the legacy codebase really is messed up beyond repair, such that even simple changes require a cascade of changes to other parts of the code. The original technology choices might be preventing you from making necessary improvements. Or, the original technology might be obsolete, making it hard (or expensive) to recruit quality developers.
The correct answer, of course, is that it depends a lot on the circumstances. Yes, sometimes it makes more sense to gradually refactor your legacy code. And yes, sometimes it makes sense to throw it all out and start over. But those aren't the only choices. Let's take a quick look at six stories, and see what lessons we can draw.
Sometimes you have to completely rewrite everything from the beginning.
Other times, changing a few words here and there, or a paragraph or two is all that is needed.
We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
Nowhere in this article is any flaw in Joel's pronouncement to never rewrite found. The only of the six stories that was a rewrite of an existing product is Netscape and that was a disaster. The fact that Firefox came out years later doesn't make it any less of a disaster.
In the rest of the cases, no one is re-writing their existing product and letting the competition catch up. No, what they are doing it making a new product and moving users over if possible. That makes sense and that is what I learned from Joel's original article.
Making this seem like some kind of intriguing rethink of rewriting legacy code is false and click-baity.
The articles own facts don't support the article's conclusions.
"Netscape’s slide into irrelevance wasn’t entirely due to the rewrite—a court agreed that Microsoft had deliberately abused their monopoly. But the rewrite was certainly a contributing factor"
The graf accompanying this section shows Netscape's market share dropping from about 80% to 50% BEFORE the rewrite. Now that drop continues from 50% to near 0% during and after the rewrite, so the rewrite certainly did not save Netscape. But the slope of the decline barely changes pre- and post-rewrite. Basically, unless there's other evidence not presented, the best conclusion is the rewrite had no effect.
Also, "what finally ended the IE6 era wasn’t Firefox but Google Chrome."
Except your own graf shows IE market share dropping starting in late 2002 in mirror to the rising Mozilla/Firefox. Chrome doesn't even show as a factor until 2008. The articles own facts don't support the article's conclusions.
What really killed Netscape was releases a lousy product. 4.0 suuuuucked. (Folks on the web in '96/97 remember.) And IE at the time was releasing it's first good version, a better version. Fact is, at that time IE was better than Netscape.
What Netscape needed was a better product, and if it took a ground-up rewrite to get that better product, then a rewrite was necessary.
What we know now is the rewrite did not save Netscape. But we'll never know if there was some other course of action that could have saved the it. What we really should be doing is examining what was going on in '95/'96 to produce such a bad product and lose that market share in the first place, not at what rearrangements of the deck chairs was done as the ship went down.
If the person recommending the rewrite is the person who wrote the original code, they are usually right.
If the person recommending the rewrite understands the code and has years of experience with it, they are often right.
If the person recommending the rewrite is the new guy fresh out of uni, they are almost certainly wrong.
Disclaimer: I was once that new guy.
You forgot:
If their title is Manager, or Consultant, they are ALWAYS wrong.
First law of people: People are generally stupid.
His article hinges upon the assumption that Netscape was screwed over by the rewrite. In reality, they were almost certainly screwed on the business side to the extent no amount of technical effort could overcome their position.
To the extent they had technical woes, it may well have been the case they couldn't sort out how to make the improvements they wanted to make given their current design.
Now there are valid points, that 'old code' may look crusty but there is a good chance it is crusty for a reason and that sort of thinking should be ever present while making such a call, to try to understand *why* it is crusty before throwing it out. However sometimes it is for bad reasons:
-Written against a once-presumed 'winner' of the market that becomes defunct. Your shockwave website has to be rewritten because the supporting technology is toast, and you better be scrapping your flash website soon if not already.
-Maybe the runtime is still around, but *your* ability to find willing developers is difficult, so you have to switch languages/runtimes to align with the labor market
-The people doing it didn't know what they were doing and did it incorrectly. Optimally, this is the same team that recognizes they painted themselves into a corner so they know what to do next time.
-The code is full of workarounds for third party libraries that no longer apply. True this doesn't scream 'rewrite', but one of his points was that the ugliness of code is due to fixes for things long forgotten that still matter, but it's frequently the case they do still matter.
In short, like all opinions be informed and influenced, but no simple answer is ever 100% correct no matter what. Internalize the points and evaluate in your scenario.
XML is like violence. If it doesn't solve the problem, use more.