Ask HN: How to tell someone you need to rewrite an entire project?

https://news.ycombinator.com/item?id=2455105

by dicarsio • 15 years ago

8 24 15 years ago

news.ycombinator.com

What should you do when you see a very bad codebase and feel that the best - and cost effective way to complete your tasks efficiently, is to rewrite the entire project and your boss is in a hurry and wants to create fixes?

profitbaron• 15 years ago

The way I would approach it is, to create a really simple table which, contains the pros of fixing the current code on one side and doing a rewrite on the other.

Then I would provide the benefits of doing both and then I'd present this to the person and say having, looked at our current code I believe that we should rewrite it because of X, Y and Z, in fact I'd even summarize this at the bottom of the table as well incase they want to take the table away and think about it.

dicarsio6• 15 years ago

I guess I'll try that. The code is poorly written and with possible bugs in it, so I can show a lot of problems to prove my point.

triviatise2• 15 years ago

Code that is working and in use is worth roughly 10x your imaginary code that doesnt exist. So unless you could prove to me that the savings or value is 10X the cost to rewrite I wouldnt do it.

Can you be more specific about why the code is bad? There are a limited set of architectural reasons for which I would support a complete rewrite. They typically correspond to non-functional requirements: 1) scale - the system architecture simply cannot support scaling 2) reliability - the system architecture is built in such a way that the system often fails 3) multi language - the system needs to be modified to support multiple languages 4) security - the system needs to be modified to support a more robust security access model etc (there are many items like this)

These things all touch every single bit of code and so could warrant a rewrite. Im skeptical of most other reasons. In most cases you can just modularize the most dangerous aspects and you will be fine.

rawsyntax• 15 years ago

I once did this. However it involved some in-depth analysis of problems with the existing code, and new ideas on how to solve the same problems. This came about because the existing code didn't really fit a feature they were trying to add on

nostrademons2• 15 years ago

Also, be very, very sure that a rewrite is the right thing to do. Probably 80-90% of the time, it isn't, and you'd be much better off with an incremental refactor.

One major way to tell: can you clearly specify what the revised version should be doing, in a way that doesn't involve "whatever the old version did"? Another litmus test: do you fully understand the old code and why it sucks the way that it does?

dicarsio6• 15 years ago

An incremental refactor is a possibility too, but almost everything must be refactored.

nostrademons2• 15 years ago

It's usually better to do things incrementally, even if the whole thing eventually needs to be rewritten and doing it incrementally takes twice as just rewriting from scratch.

16s2• 15 years ago

Quantify it. That's all most managers understand.

Customer X wants the product in 12 weeks or they're going with a competing product. Customer X may be spending 6 or 7 figures with us over the next 5 years in upfront costs and ongoing maintenance and support fees.

You may be saying, "It'll just take 6 months (24 weeks) to re-write this from scratch and do it right" (managers are used to hearing programmers say this sort of thing). For the most part, managers don't care about "doing it right" from a technical perspective, they only care about the bottom line. How is doing it right going to make more money (especially if we loose customer X in the process???)

Also, be careful when making this suggestion. Many programmers who suggest this are simply uncomfortable with other people's code. They can write stuff from scratch themselves, but can't maintain or extend code they've not written (that's always a bad sign). And to make matters worse, they always use the argument "stuff I did not write is horrible".

dicarsio6• 15 years ago

That's not the case, as there is another project in the same company with very good codebase made by one team, however, the one written by another team, sucks :-)

16s2• 15 years ago

Another risk... has a re-write been brought-up before and shot down? Did everyone agree (reluctantly) to make the best of it and continue with the code base? If that happened and you bring this up again, it may not end well. Management may see it as you undermining the project, not "being on board", etc.

So unless you feel really compelled to do this, and you can do a good, objective quantification (here is why a re-write will make us more money) as why it must be done, don't bring it up.

Also, telling mgt that a whole team in the company produces bad code may not be in your interest and it certainly won't make that team your friend going forward.

ludwigvan• 15 years ago

Send them this article: http://www.joelonsoftware.com/articles/fog0000000069.html

Then, send it to yourself.

rbanffy2• 15 years ago

There are legitimate reasons for a full rewrite.

If, for instance, you can change the platform and do the rewrite significantly faster than the original technology and implement changes faster, then the rewrite may be the may to go.

Imagine you have an app built on J2EE, with lots of logic on templates and no tests whatsoever. It's huge and maintaining it takes a huge effort. Every bug takes weeks to fix and generates wrong data that has to be corrected manually.

Imagine you can write an equivalent app in Ruby on Rails in two weeks, with tests.

Which way would you go?

jtheory4• 15 years ago

Your two "imagine" clauses are incompatible, though.

"Imagine you can write an equivalent app in Ruby on Rails in two weeks, with tests."

You've already said that the existing app has "lots of logic" and is huge. Every bug takes weeks to fix, which means the "lots of logic" is seriously twisted up and not easy to decipher.

If that's the case -- figuring out the logic to fix one bug takes weeks, then it's inconceivable that you'll untangle all of the logic in two weeks. That's before you write a single line of Ruby -- if you want an "equivalent" app, that means you have to know what the current one does, first.

This is the usually-fatal flaw in the "rewrite" argument. The existing app needs to be rewritten because no one can understand it anymore (is is both poorly-written and very large/complex). But because no one can understand it anymore, it will be extremely difficult to rewrite, unless you work as if you were creating a new, similar application.

This is also why refactoring works. You cut off a bit of the existing app, figure out just that bit, write tests for it, and then replace just that bit with new code.

You can even refactor an app into a completely different language, actually -- you have two apps running parallel, and gradually move over bits of functionality from one to the other. In the process you'll need to gradually enforce order (and separation of concerns...) on the original app, but you need to do that either way.

gersh• 15 years ago

It always depends on the circumstances. If people don't like the term rewrite, you can just call it re-factoring or adding unit testing. You are probably using something from the old codebase, right. If anyone asks why something that used to work is no longer there, you can explain that you found bugs, and so you temporarily took it out to add more testing.

Although, rewriting can be a lot of work. While there may be a temptation to rewrite everything overnight, it can be quite difficult to pull off. Although, I think devoting some time to a rewrite attempt may help you gauge the total time it will actually take. If it proves easy enough, you can go for it.

ams6110• 15 years ago

I wonder, and this is not an insult, how much experience you have as a developer. I know that for a good five years, maybe more, as a developer in corporate IT I frequently thought that I was dealing with a "very bad" codebase and rewriting seemed like an easier task than trying to understand the current system well enough to make the changes I needed to make.

I was wrong. Every time. Unless the system is quite small and single-purpose, you very likely don't understand the full scope of what it does, why it is written the way it is, which constituencies it serves, all of its interfaces, etc.

The few times I have been involved in rewrites they always took longer than expected, cost more than planned, and ended up with kludgy patches at the last minute as features of the old system that nobody talked about or knew existed suddenly became showstopper must-have requirements. In other words, they turned out like almost any other corporate IT project.

ibejoeb• 15 years ago

I'm just going to attempt to answer your question rather than question your motives.

This is the difference between software and most other forms of "construction." There are no material costs. There is no scrap to reclaim. Bits can't be reused like steel. Tearing down code is negative work. This is also goes toward the odd feeling we often have that software shares so many attributes the fine arts even though it shares so many attributes with engineering disciplines.

First: realize that the word rewrite, not the act, strikes fear into the hearts of people. Just don't say it.

Second: realize that the difference between a "fix" and "rewrite" is nil. Are you going to fix it without changing it? Not if the problem is really in the code. You don't edit out the plot hole in your novel or unpaint your landscape into a lounging nude.

Now, the answer: say you'll fix it. You're really talking about the same thing. You asserted that it would be cost-effective and efficient. To me, that implies that it will address the urgency.

It's almost always quick and easy to fix what you know is wrong. The part that makes it hard, slow, and expensive is rolling it out. For instance, it may have taken a week to design a better data model for your SaaS app vs. a month to try to find and mitigate a slow query, but now you have to figure out how to migrate all of your clients, and that's a bitch.

Ask HN: How to tell someone you need to rewrite an entire project?

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