If you can't remember why onions are in there, take 'em out.

http://garry.posterous.com/if-you-cant-remember-why-onions-are-in-there

by franze • 15 years ago

151 59 15 years ago

garry.posterous.com

the_mat• 15 years ago

There's a dangerous flip side to this: In my experience just about all programmers want to remove things from code that they don't understand or see the reason for. Why is that weird check there? Who thought it was a good idea to allocate memory that way? Very often there ARE good reasons for those decisions, and they can stem from bug fixes or odd special cases that may not be obvious..

Moral: Be careful.

hvs3• 15 years ago

Right, which is why you don't just remove the onion because you feel like it. In that story, he found out why they used to put the onion in and determined it was no longer necessary.

Moral: if you don't understand code, don't change it, understand it.

gbog2• 15 years ago

> understand it.

This has been said in some replies in this tree, but sometime you can take the piece of code you don't understand as a black box, and bridge its behavior with new code, comparing both outputs during a few iterations, then remove old code.

jsdalton• 15 years ago

Cute litte story, but the moral the author takes away from it is actually wrong.

The factory didn't remove the onions from the recipe because no one could remember why they were there. They were removed because Levi asked why they were there, and when no one remembered, he investigated the original purpose of the onions and determined after that investigation that they were no longer needed.

I'm sure many of us have been bitten by this as developers. You see a few lines of codes or a feature and you have no idea why it's there, so you remove it. What happens? Random, seemingly unrelated application starts failing or angry customer calls wondering why some feature is no longer available. Whoops...

So my takeaway from this story was actually quite different from the author's. I took: "Before you remove the onions, make sure you understand why they were added in the first place."

loup-vaillant2• 15 years ago

If the priority is to not break anything, sure, don't fix what's not broken.

Now every piece of code which is there for no know reason remains a problem. If you want to keep the code base simple, better remove either the code or your confusion (add a comment, refactor, whatever).

hvs3• 15 years ago

You should never remove code that you don't understand. And when isn't it a priority to "not break anything?"

masklinn3• 15 years ago

> If the priority is to not break anything, sure, don't fix what's not broken.

The issue generally arises because things are broken, investigation leads to a piece of code which creates the breakage (everything is perfect before, things are broken after), nothing seems to use it (the project is naturally pretty much void of automated tests), you remove the code, it fixes the issue, and then you learn that prod has started failing hard.

masklinn3• 15 years ago

> I'm sure many of us have been bitten by this as developers. You see a few lines of codes or a feature and you have no idea why it's there, so you remove it. What happens? Random, seemingly unrelated application starts failing or angry customer calls wondering why some feature is no longer available. Whoops...

Yep. Tells me OP is not a developer, and has not read the article he linked. Because the title makes no sense at all.

mechanical_fish2• 15 years ago

Before you remove the onions, make sure you understand why they were added in the first place.

Unfortunately, while this is correct, it is nowhere near strong enough.

Just because you know the initial hypothesis that drove someone to throw the onions in, doesn't mean you know what the onions are actually doing. The onions are interacting with all the other ingredients. Onions are more complicated than you think.

Before you remove the onions you must understand what they are actually doing in your recipe, not merely what you think they are doing... or you must be prepared to find out. Because even very tiny systems are generally too complicated for you to fully understand, you usually have to settle for science: You must have good enough test coverage to detect any breakage as soon as possible after the onions go out, so that you may frantically throw the onions back in and then go back to the drawing board.

And the longer the onions have been in the recipe, the longer the recipe has evolved in the presence of onions. Take the onions out and all the other changes that have happened since the onions went in might have to be tweaked. Oh, the subtle things you could find.

Here is what can happen: You'll take out the onions, and then five years later your customers will complain that your company's red paint has started peeling, ten years ahead of the fifteen-year warranty period. Oh, no. You call an all-hands meeting of your QA team. They spend months doing expensive research, while your product engineers fly from city to city trying to pacify the increasingly irate customers. Eventually the scientists find that the paint can be fixed by mixing in some kind of protein or other. But why did the paint used to work? Oops, the onions had protein in them! Sure enough, if you throw in some special Essence Of Onion Protein compound the problem goes away. Great. Now all you have to do is issue a field recall of about six years worth of your product.

You will bring this story to your CEO and the shareholders, and they will ask why you didn't just pay for some onions? Or, if removing the onions was critically important, why you didn't run a small set of onion-free test batches on a parallel process line and then put those batches through lots of tests, both in the lab and in the field, before making the change?

I've worked as a semiconductor engineer, specifically in charge of diagnosing problems that arose in the field, so believe me when I tell you that I've seen "simple", "well understood" little tweaks in a semiconductor processing recipe cost companies millions of dollars and one hell of a lot of stress. I've also lost six months of my grad student career to one specific bad step in a recipe. Once you get a working recipe you do not change a thing without a specific plan to thoroughly measure and document the effect of that change. Find someone from Intel and ask them how this works: I've heard that you can't so much as touch a knob in Intel's fabs without a signed change order.

5hoom• 15 years ago

"the longer the onions have been in the recipe, the longer the recipe has evolved in the presence of onions."

That is just an excellent explanation of why removing stuff from a working system can be so dangerous. Thank you.

wladimir• 15 years ago

With very old code bases, you need to start removing things, otherwise it becomes unmaintainable. Sure, you need good testing and code coverage to make sure you did it properly, but that applies to any change.

It doesn't mean that the people implementing it 15 years ago were idiots, no, it all made sense at the time. But after years of maintenance some parts grew into an abomination (losing any touch with the high-level design), and other parts are not needed because the specific gadget it was supposed to support no longer exists.

If you don't refactor, you'll eventually have a landmine-ridden place where every change has impact on 10 different unrelated places. A company I worked at had this problem. They had to keep adding developers to handle bugfixes and feature requests, and it only became worse instead of better because they never made available time for refactoring.

"Removing code that you don't understand" is indeed wrong and shouldn't happen, but at least if you use SCM can always look back to understand why it was added. And then remove it anyway.

Believe me, that process makes sense for a factory but for source code you eventually end up with voodoo programming. The source is too complex for any human to understand, and it is impossible to teach new developers which didn't "grow into it".

hugh3• 15 years ago

Another classic story which illustrates your point: the "Magic/More Magic" switch.

http://catb.org/jargon/html/magic-story.html

Closer examination revealed that the switch had only one wire running to it! The other end of the wire did disappear into the maze of wires inside the computer, but it's a basic fact of electricity that a switch can't do anything unless there are two wires connected to it. This switch had a wire connected on one side and no wire on its other side.

It was clear that this switch was someone's idea of a silly joke. Convinced by our reasoning that the switch was inoperative, we flipped it. The computer instantly crashed.

CapitalistCartr• 15 years ago

The story sounds to me like a call to document thoroughly. To avoid the onions write down the reasoning with every step.

vilhelm_s• 15 years ago

"Don't ever take a fence down until you know why it was put up." --Robert Frost

othello• 15 years ago

This piece of advice is quite at odds with another classic piece:

http://www.joelonsoftware.com/articles/fog0000000069.html

Back to that two page function. Yes, I know, it's just a simple function to display a window, but it has grown little hairs and stuff on it and nobody knows why. Well, I'll tell you why: those are bug fixes. One of them fixes that bug that Nancy had when she tried to install the thing on a computer that didn't have Internet Explorer. Another one fixes that bug that occurs in low memory conditions. Another one fixes that bug that occurred when the file is on a floppy disk and the user yanks out the disk in the middle. That LoadLibrary call is ugly but it makes the code work on old versions of Windows 95.

hvs3• 15 years ago

That doesn't sound like it's at odds at all. The point of the article is that you should investigate why something was done in the past so that you don't keep repeating the same thing even when it isn't necessary anymore. All of the things in your quote are still required and shouldn't be removed.

masklinn3• 15 years ago

It's at odds with the title, and in line with the content of TFA. OP used a title which has no bearing in the article he linked.

seltzered_• 15 years ago

I like to say that these are the ugly nuances where code should be commented well.

polymatter2• 15 years ago

I'd be stronger and say, if your code is going to have any comments whatsoever, this is where the comments need to be.

bradleyland• 15 years ago

If you can't remember why onions are in there, you probably need better documentation.

DanielStraight2• 15 years ago

Yes!

To me, this is the real point of the story. If you are doing anything at all non-obvious, then eventually it will make no sense at all, so write down why you did it.

MichaelApproved• 15 years ago

The trouble is, many things are obvious when we're doing it. It becomes non-obvious months/years later. Document as much as possible.

edw519• 15 years ago

Reminds me of this old story:

A religious scholar was telling his wife about the interesting discussion in class one day.

"We were attributing the reason for removing the chicken's legs before cooking it for soup."

"Reb Schalcter said it was to follow the dietary laws laid out in Leviticus."

"Reb Abraham said it was to help us retain our compassion because an innocent animal had to suffer for our benefit."

"Reb Zalman said it was because the legs were most likely to be diseased."

"I said that it was to remind us that the world, like the chicken, is broken."

"What do you think?"

His wife responded, "So that it fits in the pot."

Vivtek• 15 years ago

I heard a similar one, about a woman who had learned from her mother always to cut the ends off the roast before putting it in the oven. One day, teaching her daughter about how to cook a roast, her daughter asked why, and she realized she didn't know - so she went to her mother.

Her mother said, "I always thought it was for the taste, but I learned it from your grandmother; we should ask."

So they asked the grandmother, who said, "Oh, when your father and I got married, all we had was a very small roasting pan, so I cut off the ends of the roast so it would fit."

mrsebastian2• 15 years ago

This is basically the origin of all religions, especially 'modern' monotheistic ones.

Good, sensible ideas (at the time!) get codified. Throw in a charismatic leader of some kind who (apparently) goes around trumpeting these smart ideas. Voila, religion.

Alex3917• 15 years ago

Any dead religion is by definition not a modern religion. If you look at religious movements started within the last 50 years in the U.S., there are few if any that fit that pattern.

mrsebastian2• 15 years ago

Dangit, I was up to 5 points! And then... splat.

GlennS• 15 years ago

But onions go with everything and are delicious

dodedo• 15 years ago

Feynman used the term "cargo cult science", and others later used the term "cargo cult programming" to describe this.

http://en.wikipedia.org/wiki/Cargo_cult

Several weeks ago on HN I came across this slideshow: http://www.slideshare.net/olvemaudal/deep-c which sparked some debate as to the merits of deep, complete understanding of one's environment. I believe that those who do not have a broad understanding invent their own miniature cargo cult to get by -- or perhaps it is that they are willing to cargo cult and therefore do not develop a deep understanding?

Whatever the case, it's incredibly common in the world of software.

kinofcain• 15 years ago

I think the moral of the story for programmers should be:

If you're putting something in your code that looks like a vegetable, please put a comment on it.

Ten months down the rode you won't remember why that silly looking hack is there and neither will anyone else. It might not be applicable anymore and it might be safe to remove, or it might be holding together something critical.

pbhjpbhj• 15 years ago

Of course the onion will show you if the temperature sensors are working correctly ...

xbryanx• 15 years ago

If you can't remember why the onions are in there you've written poor documentation.

nickolai• 15 years ago

This piece of advice does not apply to legacy systems. There is a lot of stuff in there that nobody knows how it works or why it is in there, yet attempting to throw it out has led to so many disasters in the past that no one dares to even think about removing it. Of course there is no budget or political will to investigate - money comes in just fine even with the onion in the varnish.

some_g• 15 years ago

Two paragraphs of agreement with an old pg article. Why is this getting upvoted?

rhplus• 15 years ago

There was a This American Life episode a little while back that had a counter example to this anecdote: sometimes there is something in your process that makes your product special but you don't even know it until it disappears.

Audio here[1] at 34:30. A brief summary found here[2]:

"Jim Bodman, Chairman of Vienna Sausage Co. in Chicago tells the story of how the company built a brand new, state-of-the-art facility in 1970, replacing their old factory, which was actually a warren of buildings on Chicago's south side that was built up by gradually buying up buildings over the course of 70 years, until the factory complex occupied an entire city block. Once they moved into their fancy new digs, however, they faced a problem: the hot dogs weren't coming out the same. They didn't have the same distinctive red color or desired snap. They couldn't figure out what was wrong, since the ingredients, spices, cooking time, everything was the same.

After a year and a half, they still haven't figured it out...until one night, when some guys from the plant are out at a bar, reminiscing over drinks about the old days in the former plant. They start talking about Irving, a fixture at the old plant who knew everyone, whose job was to take the uncooked sausages to the smokehouse. But, given the "Rube Goldberg" layout of the old factory, it took Irving half an hour on a circuitous route to get from A to B. And they realized: Irving & his trip was the missing secret ingredient."

[1] http://www.thisamericanlife.org/radio-archives/episode/241/2... (audio at 34:30)

[2] http://theatreeastnyc.blogspot.com/2011/10/how-sausage-er-th...

pg• 15 years ago

The advice I took from Levi's story is: consider the possibility that things you take for granted as necessary actually aren't. They could be mistakes, or artifacts of limitations that have since disappeared.

(It's particularly useful for startups to notice the latter, incidentally. A lot of existing businesses turn out to be artifacts of limitations that have since disappeared. E.g. hotels are to some extent a hack to get around the fact that it used to be impossible to search all the available space in the city you wanted to visit. If you built a whole building full of bedrooms, you could afford to pay to advertise it and to pay someone to work full time taking reservations.)

eru• 15 years ago

There are also economies of scale in stuff like cleaning. And some people want quality control.

byrneseyeview• 15 years ago

GK Chesterton tells a similar, but sort of contradictory, story:

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."

In most technology fields, it seems like Onion Theory works: we can gradually get rid of the hacks we used to get round limitations. But when you're dealing with people and institutions, Fence Theory dominates: human interactions have lots of complicated nth-order effects.

Onion Theory and Fence Theory are deeply similar. In both cases, the point is: be aware of practices that don't make sense. Either they illustrate long-ago hacks and compromises, or they tell you something important but non-obvious about the nature of what you're doing.

malkia• 15 years ago

Hopefully someone would remember why circumcision is done always by certain people following certain traditions, religious rules...

contextfree• 15 years ago

What if you can't remember why you decided to adopt "If you can't remember why onions are in there, take 'em out" as one of your personal guiding maxims?

amandalim89• 15 years ago

So true. The hardest part is taking away features from your own product. We need to learn to let go of non-crucial features. built. launch fast. iterate faster.

ThaddeusQuay2• 15 years ago

http://youtube.com/watch?v=KZeiSKnhOBc (5 Monkeys)

steve8918• 15 years ago

Funny story, the 3rd job I had was at this large telecommunications company. I was doing consulting, but one of the jobs I had to do was make sure that these very important reports were generated. They had to be printed out and sent over the interoffice mail.

I figured, why not generate the reports programmatically and stick them on an intranet website (this was 1999 so "intranets" were becoming a buzzword). I asked my boss, he said okay go contact the people who need the report and see if they are okay with that.

I called the person A that normally got the reports, and they said "Oh, I don't need them, I pass them off to B". So then I called B and they said they passed it to C. This went on for about 5 people, and then it turned out that no one needed the reports. It was just something that was ingrained into the process, but no one actually needed.

The funny thing is that because no one had ownership, I could neither change the process, nor get the reports from being printed in the first place. Truly Office Space-esque

zachrose• 15 years ago

Can anyone explain in more detail how this relates to Arc and Lisp?

If you can't remember why onions are in there, take 'em out.

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