Comment by seren | Hacker News Reader

Comment by seren | Hacker News Reader

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In my open office next door, people have been refactoring a cpp98 monolith into more interdependent components to be able to have a better test suite, better CI integration, better deployment story. That sounds about right.

Well, the issue is that they have done it a bit sneakily, they removed all the legacy code they haven't understood. So the code is much more elegant, it has been moved to cpp11 or 14, it ticks every good practice. There is only one slight issue : it does not work. It somewhat work, but is not reliable and fails regularly in unexpected ways. And they've started 5 years ago, and haven't been delivering any business value since then.

At the beginning, it was okay because they had some leeway but now they are blocking the release of new products, and our market share is in free fall.

Heads have started to roll.

To be fair, a few years down the line, their team will likely be more productive and efficient, but I am still not sure that the cost of the rewrite was justified. Still the article is very on point on the risk of not paying your technical debt.

> they removed all the legacy code they haven't understood.

This is exactly why rewrites or huge refactors typically fail. The new programmer sees code and doesn't understand why the code is there and thinks the last programmer was an idiot and deletes said code. Unknown to the new programmer is that code handles some weird edge case.

A rewrite should spend 80% of the time understanding the old code and 20% writing the new. But, that's no fun for most programmers who just want to code in the latest shiny so the new code ends up broken.

Which is why it is sometimes crucial to add comments to your code. I know certain code basically documents itself, but that depends on the person who reads it. In my eyes it is precisely edge cases that might or might not be known that profit from decent explainatory comments.

As a avid writer of comments I am convinced they also help myself, to form thoughts and remember them later, so at times I will write the comments before writing an actual function.

If that is to bold, commenting while the thing is still in your head makes sense anyways — saves you time later and helps everybody else who will look at your code.

I agree. I also use git blame and track down when and why code was added. But this is tedious work that I find many people don't like to do for some reason. Me, I like the investigative work of tracking something down.

I also personally believe in, and this isn't just for code, but for any project you'll pass to another, a connected read.me file explaining the high-level reasonings and other thoughts, including a personal changelog and roadmap, and some instructions for use and editing.

And please write proper commit messages!

A short summary, preferably including a hint at which subsystem is impacted by the change. Then explain in detail the context of the change: root cause of a bug and the gist of the solution, use case(s) behind a new feature and how it can be used, ...

Yes, often there's a bug/project tracking tool being used and the commit message contains a reference to the relevant entry there. But from experience I know these tools tend to change: old one gets decommissioned, data gets migrated, what was once the primary identifier is now a mere field or comment in the new system, access rights get messed up, ... Trying to understand the history then turns into an archeological expedition through various eras long gone... unless the commit messages are sufficiently self-containing.

The issue seems to be that that tracking tool does not have its data backed up in the version control system?

This seems like it could be mitigated with an integration that watches the issue tracker for updates and then commits those updates to a docs folder on the appropriate branch of the appropriate repo.

This would have saved quite a bit of headache at my last job actually.

Or just use a version control system with issue tracker support, like Fossil ?

Switching an existing project to a new VCS loses history or at minimum causes a new layer of "identifiers in the old system don't match the new one", no?

In general, I've found value in figuring out how to improve existing systems where feasible rather than trying to migrate to a new system, since the existing system probably has advantages the new one won't. At minimum, people are already familiar with the existing system.

Of course - but I'm not sure why you assumed that I would suggest that, instead of using a different VCS for a new project.

Ah. I've spent a lot more time working on projects I inherited rather than ones where I made the initial technical decisions - if you're starting a new project, you should use the most capable tools available.

https://en.wikipedia.org/wiki/Wikipedia:Chesterton%27s_fence

"Chesterton's fence is the principle that reforms should not be made until the reasoning behind the existing state of affairs is understood. The quotation is from G. K. Chesterton's 1929 book The Thing, in the chapter entitled "The Drift from Domesticity":

In the matter of reforming things, as distinct from deforming them, there is one plain and simple principle; a principle which will probably be called a paradox. There exists in such a case a certain institution or law; let us say, for the sake of simplicity, a fence or gate erected across a road. The more modern type of reformer goes gaily up to it and says, "I don't see the use of this; let us clear it away." To which the more intelligent type of reformer will do well to answer: "If you don't see the use of it, I certainly won't let you clear it away. Go away and think. Then, when you can come back and tell me that you do see the use of it, I may allow you to destroy it."

I've taken part in a "rewrite" like what you describe. It was not the classic "Write a whole new system in parallel, then migrate everyone over." It was the Ship of Theseus executed in software, slowly, over the course of a couple years.

The lights stayed on the whole time. We retained the ability to switch back to the old system by setting a feature flag until everyone (including the business users) was confident that the new system was working as well as - preferably better than - the old one.

Throwing out code we didn't understand was simply unthinkable, because we weren't allowed to have that 6 months of time fantasizing that everything would be great before launch day - whatever you were working on now would be expected to go into production within a week or two, without upsetting the rest of the business in the process.

No, it wasn't very fun. But it was satisfying work. I think it was my boss's boss who observed that making all the team members happy won't make a project successful, but everyone's ultimately happy to see a project successfully executed.

Deleting all code you don't understand is also stretching the term "refactoring" a bit beyond its usual meaning :-)

Deleting legacy code you don't understand is the best way to remove fixes for bugs you didn't know you had.

I learned from Microsoft that rewrites are hard! (they tried it with word) and I think somewhere is the story how it went.. They rolled back later on and kept modernizing piece by piece now.

That, I think is the right way.

To play the devil's advocate: it might not be a one size fits all solution.

When you're at Microsoft and can just walk up to the bar researchers and programmers in the world, maybe. When you're at some corporation where you have to spend half a day on the phone to get your computer unlocked by the desktop support and request to change a config on a web server becomes a ten foot long email chain about whose fault it is that we need this change, I don't think people have any motivation to modernize piece by piece.

Then there is the issue that you'll have to explain why part of the application is in .NET core and part is in dot net framework 3.5...

> ...and I think somewhere is the story how it went...

Maybe this? https://blogs.msdn.microsoft.com/rick_schaut/2004/02/26/mac-...

Couldn't find any other reference, nice reading!

The legacy code should have been running in parrallel with the new code , atleast until it reaches feature parity ( or reduced features - with other features removed as they have not been used)

Definitely it is a text book example of things to not do, but what is painful is that they started with good intentions. (People with good intentions are the most dangerous one though)

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