Accidentally Load Bearing

https://www.jefftk.com/p/accidentally-load-bearing

by jamessun • 3 years ago

441 196 3 years ago

pickledish• 3 years ago

This (the unimportant stud becoming load bearing later on) makes sense, but in my experience it’s kind of a sign of lazy design. When making software at least, you know when you’re trying to use a decorative stud to hold up part of your house, and choosing to do it anyway instead of building some new better structure does make for a pretty sad dev team later on

This is to say —- I agree with the article, but much nicer is to work at a place where you don’t expect to make this particular discovery very often, hah

Qwertious• 3 years ago

s/lazy/lack of/

Hidden files in unix were a bug.

troupo• 3 years ago

And then .DS_Store in MacOS was basically a bug, too. A lack of understanding coupled with a lack of design.

herpdyderp• 3 years ago

you know when

More often than not I've seen this happen because they, in fact, do not know.

bgribble• 3 years ago

you know when you’re trying to use a decorative stud to hold up part of your house

"You" might know it in "your" creations, but in my career I am much more often working and reworking in other people's creations.

I think the point of the article is not that you should avoid using decorative studs as load-bearing elements, but that you should be aware that others may have done so before you came along.

This is an even more conservative position than the default Chesterton's Fence reading, which is itself dismissed by a lot of people as pedantically restrictive.

For me, the parent article resonates. I have definitely had ceilings come crashing down on my head when I removed a piece of "ornamental" trim (programmatically speaking)

jerf2• 3 years ago

"This is an even more conservative position than the default Chesterton's Fence reading, which is itself dismissed by a lot of people as pedantically restrictive."

In a normal, real-life context, I can see why someone would feel that way.

In a software engineering context I think it's just a further emphasis that you ought to understand what something is doing before fiddling with it, and both the original intent and what it is currently doing are interesting information. Many times I've removed dead code, only to learn that not only was it alive (which wouldn't have been that surprising, it's easy to miss some little thing), but that it is very alive and actually a critical component of the system through some aspect I didn't even know existed, which means I badly screwed up my analysis.

The differences between the physical world and the software world greatly amplify the value of the Chesterton's Fence metric. In the physical world we can all use our eyes and clearly see what is going on, and while maybe there's still a hidden reason for the fence that doesn't leap to mind, it's still a 3-dimensional physical problem in the end. Software is so much more interconnected and has so much less regard for physical dimensions that it is much easier to miss relationships at a casual glance. Fortunately if we try, it's actually easier to create a complete understanding of what a given piece of code does, but it is something we have to try at... the "default view" we tend to end up with of software leaves a lot more places for things to hide on us. We must systematically examine the situation with intention. If you don't have time, desire, or ability to do that, the Chesterton's Fence heuristic is more important.

We're also more prone to drown under Chesterton's fences if we're not careful, though. I've been in code bases where everyone is terrified to touch everything because it seems like everything depends on everything and the slightest change breaks everything. We have to be careful not to overuse the heuristic too. Software engineering is hard.

bjornasm• 3 years ago

When making software at least, you know when you’re trying to use a decorative stud to hold up part of your house

Do you? Sometimes quick-one-time fixes becomes the center of important software.

andrewaylett• 3 years ago

I've been happily running a service that's non-critical, only to discover when we have an outage (that should be a non-event) that another team has started relying on it for something business critical.

jefftk8• 3 years ago

This was famously a problem for Google's distributed lock service, Chubby. They handled it by intentionally having outages to flush out ways it might have started to bear loads it wasn't designed for: https://sre.google/sre-book/service-level-objectives/#xref_r...

cesaref2• 3 years ago

Well, let's say you are working on a well engineered and tested product, and you look at the code coverage, and there's a whole lump of functionality that has no coverage.

You could conclude that the code is unnecessary and remove it, or you could conclude that some test cases need to be added to exercise it. How do you decide which is correct?

The problem is usually that well thought and and designed software was build for a moving target, and invariably things have changed over time. It's not necessarily a sign of lazy design, it's where the real world intersects with the nice neat pretend world we design for :)

convolvatron2• 3 years ago

I'm deeply frustrated at the missing answer here. read the code. figure out what's it for. take out it and see what breaks. software is not a house, you can completely wreck it and set in back exactly the way it was in a second.

there is no excuse for not owning and knowing the software you are supposed to be in control of.

dylan604• 3 years ago

When making software at least, you know when you’re trying to use a decorative stud to hold up part of your house, and choosing to do it anyway instead

Whenever I find myself doing this, I at least leave a comment typically worded along the lines of "the dev is too lazy, not enough time to do it right, or just has no clue what to do, so here you go..."

dkarl• 3 years ago

in my experience it’s kind of a sign of lazy design

Is it always lazy in the bad way, though? In software there's no sharp distinction between "built to carry weight" and "built to tack drywall onto." Whether a system is robust or dangerously unscalable depends on the context. You can always do the thought experiment, "What if our sales team doubled in size and then sold and onboarded customers as fast as they could until we had 100% of the market," and maybe using your database as a message queue is fine for that.

If it results in a sad dev team, then that's a case where it was a mistake. It's hard to maintain, or it's an operational nightmare. That isn't the inevitable result of using a (software) decorative stud as a (software) load-bearing element, though. There are a lot of systems happily and invisibly doing jobs they weren't designed for, saving months of work building a "proper" solution.

im3w1l• 3 years ago

Let's say you code defensively. You add some handling invalid input to your function. Because the rest of your codebase never sends it invalid input it's dead code - not load bearing. Until at some point a bug is introduced and sends you invalid input which is then dutifully handled and recovered from. The branch has become load bearing.

hprotagonist• 3 years ago

reminds me of Hyrum’s law a bit.

kuchenbecker2• 3 years ago

It is Hyrums law. The observable feature of the board was that it could bear load despite that not being the intention, and the house started using this observable feature.

jefftk8• 3 years ago

> Hyrum’s law
It is Hyrums law.

No, it's "Hyrum's" not "Hyrums": https://www.hyrumslaw.com/

ochoseis• 3 years ago

One benefit software has over physical systems is that you can easily document it right inside the code with comments and types to make the intention clearer. This isn’t foolproof, especially in dynamic languages like Python, but helps a lot.

The analogy for the load bearing stud might be a hackathon project that never expected to see production. In reality, a lot of what we do is hack on something until it barely works, and move on to the next thing.

eschneider2• 3 years ago

That's easy to do, if it's _intentional_. I'm always amazed at how often I see systems rate limited by some seemingly "decorative" upstream component, that when removed, causes everything else to run amok. :/

MilStdJunkie• 3 years ago

Yuuuuuup. This precise set of problems is why Systems Engineering was adopted in Aerospace and Defense, because maintenance plans need to know what the "loads" are for each replaceable (spareable) unit or assembly.

Today's SE has wandered far, far afield from original goals, tragically enough, but that was the original conception. One of the reasons for today's relatively toothless SE departments is the rise of finance into maintenance planning. Inventory depreciation is a cruel mistress, and "what gets spared" is rarely a SE judgement these days, at least in my experience. This has predictable results, but is partially offset by the exceptionally high bar for aerospace maintenance staff, who are generally pretty damn badass compared to, say, a washing machine repairman. Finance, naturally, would like to knock that bar down a few pegs, too.

mcv• 3 years ago

I've definitely had this happen. With my own code, even. I build something complex, it's released to production, and a few months later I realise that something about it should be done in a different way, so I look at it, and other people have already built on top of the thing I wanted to change.

On the other hand, if you can't figure out what something is for, sometimes the easiest way to find out is to remove it and see what breaks. Maybe that's not such a great idea for that load-bearing stud, but in software it's easy to undo.

binarymax• 3 years ago

I feel like part of the story is missing. Did he remove the stud and learn the hard way?

jefftk8• 3 years ago

> How did you find out the closet partition stud was load bearing, in the end ?
I tried to cut it and it started to bind the saw. I stopped and thought, and then did not cut anymore until I had shored up the upstairs.

https://www.jefftk.com/p/accidentally-load-bearing#fb-231219...

h2odragon• 3 years ago

A smack with a hammer can tell you all sorts of things. If the board is rotten; some is likely to come off. If it's under tension it'll sing out with a resonance absent from a board carrying only its own weight.

In your circumstance, the board should have had some wiggle but prolly wouldn't have.

Ensorceled• 3 years ago

> I tried to cut it and it started to bind the saw. I stopped and thought, and then did not cut anymore until I had shored up the upstairs.

This is exactly I found out that a stud was now load bearing.

geocrasher• 3 years ago

This reminds me of end users who unknowingly exploit a bug in a piece of software and integrate it into their normal workflow. The result is that when the bug is fixed, their workflow is interrupted, causing complaints.

gerad• 3 years ago

https://xkcd.com/1172/

Karellen2• 3 years ago

More formally:

With a sufficient number of users of an API, it does not matter what you promise in the contract: all observable behaviors of your system will be depended on by somebody.

https://www.hyrumslaw.com/

OldGuyInTheClub• 3 years ago

Also the denouement to the Fawlty Towers "Builders" episode.

https://www.youtube.com/watch?v=jfBOIbjbLv0

(or, jump to https://youtu.be/jfBOIbjbLv0?t=1560)

dudeinjapan• 3 years ago

I’m a believer in making a “Single Responsibility: ___” comment at the top of each class.

marcosdumay3• 3 years ago

If your class name doesn't answer it, that comment won't either.

irisgrunn• 3 years ago

I had something similar. A couple of years ago I bought on old house. The previous owners did most of the work themselves from the 1960s on.

The zinc gutter had leaked for probably decades and it destroyed part of the roof structure. The roof was held up by the wooden paneling the used to cover it on the inside (70s). So the wooden paneling was actually load bearing

Actually I've found way more stuff in this house. For example at the end of the roof the tiles weren't wide enough and instead of buying extra roofing tiles, they decided to fill it with cement and pieces of ceramic flower pots.

dmbche2• 3 years ago

Degrees away from load bearing paint!

hef198983• 3 years ago

Or a poster!

bcrosby95• 3 years ago

I had a house that had really bad termite damage and the contractor called it "structural stucco".

hinkley10• 3 years ago

PSA: houses don't 'get termites'. They get water damage, and then the water damage gets termites.

Most problems with houses come back to managing water, air, or some other infiltration. But mostly it's water.

UncleEntity• 3 years ago

Yep, sounds like my garage.

At first look it seem like someone backed into the garage door and mangled the hell out of it but on more careful inspection the roof is being barely held up by the tracks that the door runs in and is pretty near to giving up the ghost. Was just going to splice the ends of the rafters (like someone did on the other side who knows how many years ago...if it works, it works) and replace the garage door but now its looking like I'll need a whole new roof.

What really worries me is the dodgy wiring strung all across the basement which is a combination of newish wires, old cloth covered wires and liberal applications of electrical tape to splice it all together. Luckily none of the wires seem to be load bearing...

bombcar3• 3 years ago

Carefully reading the NEC indicates that loads of electrical tape is permitted way more often than you’d think it should …

hinkley10• 3 years ago

The thing I learned when we fixed our old house up for sale, is that in some municipalities you need a building permit to replace a floor that already exists with a new one. In our case water damage was from a claw foot tub drain, which I had fixed but years after the problem started, so it was in the middle of the floor. The contractor ripped it down to the joists and doubled them, which does not it turns out require a permit.

Sounds like your guy had a similar experience.

jedberg• 3 years ago

I had to do a garage roof a few years ago. The previous owner thought it would be a good idea to put a hole in the main crossbeam to attach the garage door opener. As soon as I bought the house I removed the garage door opener and put metal plates on both side of the hole bolted together.

My "fix" held for about 11 years, but apparently it very slowly weakened, creating a small divot on the roof. Which got bigger and bigger with each rain, but since I never go on the garage roof, I didn't notice.

Until during one heavy rain I got a surprise skylight!

So yeah, you probably want to fix that before you get a total collapse like I did.

hinkley10• 3 years ago

If you go back to the early 1900s, the cladding was installed on a diagonal, which helped greatly in preventing the building from racking. Now we rely on sheet rock and plywood to provide that protection in earthquakes and wind storms.

If you ever see a house stripped down to the sticks for a rebuild, you will hopefully notice a few braces added. Not to keep the walls from falling down, but to keep them square and true until the walls are rebuilt.

jefftk8• 3 years ago

For what it's worth, in the Boston area traditional sheathing is boards parallel to the ground, not diagonal.

(I've seen dozens of houses from ~1900-1920 in the process of full gut rebuilds, and none of them had diagonally installed sheathing.)

TheCapn6• 3 years ago

Huh. Finally a name for it.

I do a lot of support work for Control Systems. It isn't unheard to find a chunk of PLC code that treats some sort of physical equipment in a unique way that unintentionally creates problems. I like to parrot a line I heard elsewhere: "Every time Software is used to fix a [Electrical/Mechanical] problem, a Gremlin is born".

But often enough when I find a root cause of a bug, or some sort of programmed limitation, the client wants removed. I always refuse until I can find out why that code exists. Nobody puts code in there for no reason, so I need to know why we have a timer, or an override in the first place. Often the answer is the problem it was solving no longer exists, and that's excellent, but for all the times where that code was put there to prevent something from happening and the client had a bunch of staff turnover, the original purpose is lost. Without documentation telling me why it was done that way I'm very cautious to immediately undo someone else's work.

I suppose the other aspect is knowing that I trust my coworkers. They don't (typically) do something for no good reason. If it is in there, it is there for a purpose and I must trust my coworkers to have done their due diligence in the first place. If that trust breaks down then everything becomes more difficult to make decisions on.

smallpipe• 3 years ago

I suppose the other aspect is knowing that I trust my coworkers. They don't (typically) do something for no good reason

This so much. Depending on the git blame, I'll either remove it blindly or actually think about it way more.

letitbeirie2• 3 years ago

The most haunting comment line I've ever seen was buried deep in an Allen Bradley PLC:

I don't know why this rung is needed but delete it and see what happens for yourself

Did not fuck around; did not find out.

mauvehaus• 3 years ago

Context for those who haven't worked in the field: A PLC is a programmable logic controller. They are typically programmed with ladder logic which grew out of discrete relay based control systems.

Generally they're controlling industrial equipment of some sort, and making changes without a thorough understanding of what's happening now and how your change will affect the equipment and process is frowned upon.

https://en.wikipedia.org/wiki/Ladder_logic

sumtechguy• 3 years ago

but now its like the number of licks to the center of tootsie pop the world may never know!

praptak2• 3 years ago

This has the "more magic" anecdote feel to it.

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

weaksauce2• 3 years ago

do you remember what the instruction was?

Karellen2• 3 years ago

But often enough when I find a root cause of a bug, or some sort of programmed limitation, the client wants removed. I always refuse until I can find out why that code exists. Nobody puts code in there for no reason, so I need to know why we have a timer, or an override in the first place.

Isn't that just the regular Chesterton's Fence argument though?

The one the article is specifically written to point out is not enough by itself, because you need to know what else has been built with the assumption that that code is there?

TheCapn6• 3 years ago

All my comment is adding a software anecdote to the story. It really is just regular Chesterton's Fence, a term I've never heard until now but dealt with for the last several years.

You're not wrong, but in the context of a PLC controlling a motor or gate it is far more segregated than the code you're probably thinking of. Having a timer override on a single gate's position limit sensor would have no effect on a separate sensor/gate/motor.

If the gate's function block had specific code built into it that affected all gates then what you're talking about would be more applicable.

cortesoft• 3 years ago

This sounds more like the original Chesterton’s fence than what the article is describing. The article is about understanding something’s actual current purpose, rather than just the intended purpose.

What the article is describing reminds me of the XKCD comic workflow: https://xkcd.com/1172/

A system exists external to the creators original purpose, and can take on purposes that were never intended but naturally evolve. It isn’t enough to say “well that is not in the spec”, because that doesn’t change reality.

causi2• 3 years ago

I'll never do PLC work again. Forget undocumented code, most of the time there's no schematics for the hardware you're working on because it was custom-built thirty years ago.

TheCapn6• 3 years ago

My company is generally good about that. We have lots of overlapping documentation that answers questions like that in different ways. From Electrical schemas to QA docs, picture archives of panels and wiring, ticketing systems, spreadsheets over I/O, etc. etc.

I hate PLC work for other reasons. I'm starting to look at going back to more traditional software role. I'm a bit tired of the road work and find the compensation for the amount asked of you to be drastically underwhelming. This meme is very much relevant:

https://i.redd.it/rawo5uki1v9b1.jpg

bamfly• 3 years ago

This is why I comment a "why" for any line of code that's not incredibly obvious. And 100% of the time when it's due to interaction with something outside the codebase, whether that's an OS, filesystem, database, HTTP endpoint, hardware, whatever, if it's not some straightforward call to some API or library.

Sleep due to rate limiting from another service? COMMENT. Who's requiring it, the limits if I know exactly what they are at the time (and noting that I do not and this is just an educated guess that seems to work, if not), what the system behavior might look like if it's exceeded (if I know). Using a database for something trivial the filesystem could plausibly do, but in-fact cannot for very good reasons (say, your only ergonomic way to access the FS the way that you need to, in that environment, results in resource exhaustion via runaway syscalls under load)? Comment. Workaround for a bug in some widely-used library that Ubuntu inexplicably refuses to fix in their LTS release? Comment. That kind of thing.

I have written so very many "yes, I know this sucks, but here's why..." comments.

I also do it when I write code that I know won't do well at larger scale, but can't be bothered to make it more scalable just then, and it doesn't need to be under current expectations (which, 99% of the time, ends up being fine indefinitely). But that may be more about protecting my ego. :-) "Yes, I know this is reading the whole file into memory, but since this is just a batch-job program with an infrequent and predictable invocation and this file is expected to be smallish... whatever. If you're running out of memory, maybe start debugging here. If you're turning this into something invoked on-demand, maybe rewrite this." At least they know I knew it'd break, LOL.

MrBuddyCasino2• 3 years ago

You're doing the lords work. I often get pushback on doing this with some variation of "comments bad, code should be self-documenting". This is unwise, because there are "what code does" and "why code does" comments, but this turns out to be to nuanced to battle the meme.

csours3• 3 years ago

There was some inscrutable code that had sleep 10 [seconds] in the middle.

It took several hours to figure it out, but the sleep was there in case a file had not finished downloading

overnight53493• 3 years ago

Hah, I did one of these just last week. There's some sort of silicon bug or incorrect documentation that causes this lithium battery charger to read the charge current at half of what it should be. This could cause the battery to literally explode, so I left a big comment with lots of warnings explaining why I'm sending "incorrect" config values to the charge controller.

It's absolutely imperative that the next guy knows what the fuck I'm doing by tampering with safety limits.

gav• 3 years ago

I like to make sure the "why" is documented, but it's hard to get people to care about that.

I remember a former client tracking me down to ask about a bug that they had struggled to fix for months. There was a comment that I'd left 10 years earlier saying that while the logic was confusing, there was a good reason it was like that. Another developer had come along and commented out the line of code, leaving a comment saying that it was confusing!

mike_hock• 3 years ago

The last part is also useful. Tells the next person where to look when they do run into scaling issues, and also tells them that there wasn't some other reason to do it.

jasfi• 3 years ago

I like to write frequent comments, so that I can just scan the comments (only) of a function to know how and why it does what it does.

jrs2352• 3 years ago

I like to add the date the why comment was added and the date the comment was last reviewed/veified as still true/neccesary (which will rarely differ because they are seldomly reviewed/re-verified).

COMMENT WRITTEN: 2023-03-21

COMMENT LAST REVIEWED/VERIFIED AS STILL TRUE: 2023-05-04

WHY THIS CODE: This sucks but ...

ke88y3• 3 years ago

I do a lot of support work for Control Systems. It isn't unheard to find a chunk of PLC code that treats some sort of physical equipment in a unique way that unintentionally creates problems. I like to parrot a line I heard elsewhere: "Every time Software to fix a [Electrical/Mechanical] problem, a Gremlin is born".

At least some of this is cultural. EEs and MEs have historically viewed software less seriously than electrical and mechanical systems. As a result, engineering cultures dominated by EEs/MEs tend to produce shit code. Inexcusably incompetent software engineering remains common among ostensibly Professional Engineers.

hef198983• 3 years ago

On the other hand there was Juicero...

TheCapn6• 3 years ago

You're not wrong. It shows in the state of PLC/HMI Development tools. Even simple things like Revision Control is decades behind in some cases.

I've basically found my niche in the industry as a Software Engineer though I can't say I see myself staying in the industry much longer. The amount of time's I've gotten my hands on code published by my EE coworkers only to rewrite it to work 10x faster at half the size with less bugs? Yikes. HMI/PLC work is almost like working in C++ at times, there's so many potential pitfalls for people that don't really understand the entire system, but the mentality by EE/ME types in the industry is to treat the software as a second class citizen.

Even the clients treat their IT/OT systems that way. A production mill has super strict service intervals with very defined procedures to make sure there is NO downtime to production. But get the very same management team to build a redundant SCADA server? Or even have them schedule regular reboots? God no.

liminalsunset2• 3 years ago

I think one of the reasons I've seen this happen is because typically, EE and ME programs in university teach very little CS "enough to be dangerous", and the few coding projects you are required to do are often taught in a way that downplays the importance of the software. Software is often seen as simply a translation or manifestation of a classical mathematical model or control system ( or even directly generated by Matlab/Simulink).

Software, being less familiar, is not viewed as a fundamental architectural component because there often isn't sufficient understanding of the structure or nuance involved in building it. In my experiences software or firmware engineers tend to be isolated from the people who designed the physical systems, and a lot of meaning is lost between the two teams because the software side does not understand the limitations and principles of the hardware and the hardware team does not understand the capabilities and limitations of the software.

peteradio• 3 years ago

"Every time Software to fix a [Electrical/Mechanical] problem, a Gremlin is born".

I think I get the gist, but that sentence is missing some words.

TheCapn6• 3 years ago

oooboy is it. That's what I get for not proofreading.

hinkley10• 3 years ago

Nobody puts code in there for no reason, so I need to know why we have a timer, or an override in the first place.

I would like to think that if I sent out an email about git hygiene that you would support me against the people who don’t understand why I get grumpy at them for commits that are fifty times as long as the commit message, and mix four concerns two of which aren’t mentioned at all.

Git history is useless until you need it, and then it’s priceless.

I can’t always tell what I meant by a block of code I wrote two years ago, let alone what you meant by one you wrote five years ago.

scubbo4• 3 years ago

commits that are fifty times as long as the commit message

One of my proudest commits had a 1:30 commit:message length ratio. The change may have only been ~3 lines, but boy was there a lot of knowledge represented there!

throw9away6• 3 years ago

Sometimes you have to remove the chunk and see what breaks because the person that put it in is long gone and documentation is missing

xen2xen1• 3 years ago

cough 737 Max cough

alex-robbins• 3 years ago

"Every time Software is used to fix a [Electrical/Mechanical] problem, a Gremlin is born"

I'm definitely going to use this, and I think there's a more general statement: "Every time software is used to fix a problem in a lower layer (which may also be software), a gremlin is born."

glonq• 3 years ago

"Every time Software is used to fix a [Electrical/Mechanical] problem, a Gremlin is born"

Early in my career, I was confused by seemingly-crazy questions in the Hacker Test (https://www-users.york.ac.uk/~ss44/joke/hacker.htm) like...

0133 Ever fix a hardware problem in software?
0134 ... Vice versa?

But after spending years developing embedded systems, I don't even blink at such questions. Yes, of course I have committed such necessarily evils!

HeyLaughingBoy• 3 years ago

"Every time Software is used to fix a [Electrical/Mechanical] problem, a Gremlin is born".

Just did one of those this morning. Hmmm.

Izkata2• 3 years ago

"Every time Software is used to fix a [Electrical/Mechanical] problem, a Gremlin is born"

Gizmo caca.

(...I just watched both Gremlins movies last weekend...)

dacox• 3 years ago

The unspoken thing here is that PLC code often(usually?) isn't exactly written in text, or in a format readable by anything other than the PLC programming software.

After a year long foray into the world of PLC, I felt like I was programming in the dark ages.

I'm assuming its a bit better at very big plants/operations, but still.

kvmet• 3 years ago

I work with control systems and have a similar mantra: "You can't overcome physics with software." It's super common to have someone ask if a mechanical/human/electrical/process issue can be fixed with software because people believe that programming time is free. Sometimes it's not even that it's impossible to do in software, but adding unnecessary complexity almost always backfires and you'll wind up fixing it the right way anyway in the end.

woleium• 3 years ago

Chesterton's Fence is a principle that says change should not be made until the reasoning behind the current state of affairs is understood. It says the rash move, upon coming across a fence, would be to tear it down without understanding why it was put up.

csours3• 3 years ago

See also "Swiss Cheese Accident Model" and Melted Cheese Accident Model. Also see also Stockton Rush's statements on safety. He said that most accidents are caused by operator error, so making the sub strong enough wouldn't affect safety.

marcosdumay3• 3 years ago

What is that molten cheese accident model? Are you trying to describe deviance normalization?

csours3• 3 years ago

Molten cheese means that something that was intended to increase safety became a hazard during an incident.

Think of how the SCRAM at Pripyat/Chernobyl caused the reactor to go supercritical because of the graphite tips. The control rods should have reduced reactivity in the reactor, but the first section of the rod increased reactivity.

Or how a hard hat dropped from a height may cause injury.

rkagerer• 3 years ago

Part of writing and maintaining good code is maintaining useful documentation (such as comments) expressing clear rationale and intent. Simple stuff can be elegantly implicit, and modern languages are getting better at capturing more of this in syntax and eliminating common footguns. But more complex systems tend to benefit from explicit explanation or even external design documents (like diagrams). A fix that doesn't keep those current isn't a completed fix.

When I come in on a consulting basis I often have to help developers unwind the unintended effects of years of patches before we can safely make seemingly-simple changes. It's analysis-intensive, and like an archaeologist any artifacts I can dig up that you've left behind providing clues to what was in your head at the time can be helpful. In some cases where a set of functions is super critical we've made it part of the culture every time altered code is checked in to perform a walkthrough analysis to uncover any fresh unintended side-effects, ensure adherence to design requirements and discover and spotlight non-obvious relationships. The key is to turn the unintended or non-obvious into explicit. Sounds painful but in practice due to the high risk attached to getting that portion of code wrong the developers actually love that time for this is worked into the project schedules - it helps them build confidence the alteration is correct and safe.

I wish it were easier to impress the importance of this on inexperienced developers without them having to go through the hell of maintaining code in an environment where it was lacking.

It's a skill and art to keep the appropriate level of conciseness to avoid the documentation (no matter which form it takes) becoming too verbose or unwieldy to be helpful.

latchkey• 3 years ago

document the why, not the what.

this is also why tests are so important. if you want to remove something, you have to think twice... once for the original code and once to fix the broken tests.

regularfry• 3 years ago

That has saved me more times than I care to count. "Oh, that's why that code was there. I see."

Izkata2• 3 years ago

and like an archaeologist any artifacts I can dig up that you've left behind providing clues to what was in your head at the time can be helpful.

This is why I'm against squashing commits in git, that our other development teams don't understand: you're going through extra effort to make it more difficult in the future.

dmbche2• 3 years ago

The term load bearing always bring to my mind the breakdown of how the towers failed during 911 - especially how the plane cutting a lot of vertical steel beams redistributed the weight of the building onto other beams that were not rated to hold most of the buildings weight (while being heated) - they buckle and fail.

Guess I'm thinking of being very aware of how the structure reacts to failure, and not necessarily the strenght of all individual parts.

themillerdave• 3 years ago

I always refer to this as "Load-bearing wallpaper" - in so much that folks who see it, wouldn't think twice about tearing it down - it's wallpaper, right? Well, turns out it was load-bearing wallpaper and the house came down as a result.

cratermoon• 3 years ago

This could be considered a variant of Hyrum's Law: "With a sufficient number of users of an API, it does not matter what you promise in the contract: all observable behaviors of your system will be depended on by somebody". At some point the stud was became a structural member, because other changes made it so. Now the second floor depends on it, and removing it would compromise the structural integrity of the second floor.

dclowd9901• 3 years ago

This is precisely the reason so many developers have come to love functional programming and side-effect-free designs. If that stud _can't_ affect anything outside of its original intended purpose, it can more easily be understood for its purpose and maintained or removed more easily.

wellpast• 3 years ago

What I've learned from decades of software development: ANY and every component or capability you build into your system, incidentally or explicitly, will immediately (ie tomorrow) become "Accidentally Load Bearing".

Dependencies flow in and onto new components like water. This is a fundamental law.

Even secret interfaces, etc that you think no one could find or touch will be found and fondled and depended upon.

This is why the correct view is that all software is a liability and we should write as little of it as possible, just the minimal that is needed to get the dollars and nothing more.

hinkley10• 3 years ago

I’ve been using, “that was a load bearing poster” for years. Usually right after a P1 and right before an RCA.

Simon_O_Rourke• 3 years ago

Good Gawd! A stud holding up a second floor by itself... time to have that domicile condemned and the inhabitants moved out asap!

Cerium• 3 years ago

The only option is to do a complete rebuild. The load bearing stud indicates that the foundation design was inadequate for current needs.

jefftk8• 3 years ago

The closet partition stud was bearing enough load to matter, but it wasn't holding up the whole second floor by itself.

I put in a new beam to replace the load bearing wall the preivous-previous owners had removed, with posts down to the basement: https://www.jefftk.com/p/bathroom-construction-framing

7402• 3 years ago

I used to work with a physics postdoc who would sometime leave a sign on an equipment setup that read, "Do not touch. There are hidden dangers."

The lab was full of smart people who were used to looking at things and making their own well-reasoned conclusions about whether it was OK to change something. This was a warning not to be too hasty about doing that!

w10-1• 3 years ago

This article and every other comment seems to miss the real issue: the lack of testing.

Software differs from all other means of production in that we can in fact test any change we make before realizing it in the world.

With good tests, I don't care what the intent was, or whether this feature has grown new uses or or new users. I "fix" it and run the tests, and they indicate whether the fix is good.

With good tests, there's no need for software archeology, the grizzled old veteran who knows every crack, the new wunderkind who can model complex systems in her brain, the comprehensive requirements documentation, or the tentative deploy systems that force user sub-populations to act as lab rats.

Indeed, with good tests, I could randomly change the system and stop when I get improvements (exactly how Google reports AI "developed" improvements to sorting).

And yet, test developers are paid half or less, test departments are relatively small, QA is put on a fixed and limited schedule, and no tech hero ever rose up through QA. Because it's derivative and reactive?

mucle6• 3 years ago

Chesterton's Test

jefftk8• 3 years ago

With good tests, I don't care what the intent was, or whether this feature has grown new uses or or new users. I "fix" it and run the tests, and they indicate whether the fix is good.

Except when the tests verify what the code was designed to do, but other systems have grown dependencies on what the code actually does.

Or when you're removing unused code and its associated tests, but it turns out the code is still used.

Or when your change fails tests, but only because the tests are brittle so you fix the test to match the new situation. Except it turns out something had grown a dependency on the old behavior.

Tests are great, and for sufficiently self contained systems they can be all you need. In larger systems, though, sometimes you also need telemetry and/or staged rollouts.

conor-• 3 years ago

Except when the tests verify what the code was designed to do, but other systems have grown dependencies on what the code actually does.

Assuming you mean systems in terms of actually separate systems communicating via some type of messaging, isn't that where strong enforcement of a contract comes into play so that downstream doesn't have to care about what the code actually does as long as it produces a correct message?

Or when your change fails tests, but only because the tests are brittle so you fix the test to match the new situation. Except it turns out something had grown a dependency on the old behavior.

I think this supports GPs point about tests being second-class and not receiving the same level of upkeep or care that the application code receives and one can argue that you should try to prevent being in a position where tests become so brittle you end up with transient dependencies on behavior that was not clear.

fardo• 3 years ago

the lack of testing

Having worked on very long-running projects, testing or well-funded QA doesn’t tend to save you from organizational issues.

What typically seems to happen is tests rot, as tests often seem to have a shelf life. Eventually some subset of the tests start to die - usually because of some combination of dependency issues, API expectations changes, security updates, account and credential expirations, machine endpoint and state updates, and so on - and because the results from the test no longer indicate correctness of the program, and the marginal business value of fixing one individual broken test is typically very low, they often either get shut off entirely, or are “forced to pass” even if they ought to be an error.

Repeat for a decade or two and there quickly start being “the tests we actually trust”, and “the tests we’re too busy to actually fix or clean up.”

Which tests are the good ones and bad ones quickly become tribal knowledge that gets lost with job and role changes, and at some point, the mass of “tests that are lying that they’re working” and “tests we no longer care to figure out if they’re telling the truth that they’re failing” itself becomes accidentally load-bearing.

joe_the_user• 3 years ago

And yet, test developers are paid half or less, test departments are relatively small...

Huh? Your first part seemed to be repeating TDD optimism but then you switch test departments. Just make your claims consistent, I'd suggest you instead talk about tests being written by the programmers, kept with the code and automatically run with the build process.

However, I don't think even TDD done right can replace good design and good practices. Notably, even very simple specifications can't be replaced by tests; if f(S) just specified to spit out a string concatenated with itself, there's not obvious test treating f as a black box that verifies that f is correct. Formal specifications matter, etc. You can spot check this but if the situation is one magic wrong value screws you in some way, then your test won't show this.

there's no need for software archeology, the grizzled old veteran who knows every crack, the new wunderkind who can model complex systems in her brain, the comprehensive requirements documentation, or the tentative deploy systems that force user sub-populations to act as lab rats.

Wow, sure, all that stuff can be parodied but it's all a response to software being hard. And software is hard, sorry.

hinkley10• 3 years ago

Probably the most shocking revelation I've had in my time as a developer has been that testers are never paid the correct salary (some too high, most too low), and that if you have someone who is good at testing and is becoming proficient at coding, their smartest move is not to become a FT developer, but to skip right over developing and go into security consulting. Instead of making 75% more money by switching careers, you can make 150% more.

Software needs people with the suspicious minds of good testers, but security people make more money for the same skillset.

perrygeo• 3 years ago

test developers? test departments? QA teams? It's worth mentioning that the vast majority of software orgs don't have the luxury of such distinctions, i.e. software teams are generally directly responsible for the quality of their own work and can't punt problems across the org chart.

makeitdouble• 3 years ago

To extend on jefftk's point, the tests have a specific scope (what the code is responsible for), which probably doesn't cover what it is now expected to do after months/years of getting used.

Your code was supposed to calculate the VAT for a list of purchases, but progressively becomes a way to also force update the VAT cache for each product category and will be called in originally unexpected contexts.

BTW this is the same for comments: they'll cover the original intent and side effects, but not what the method/class is used for or actually does way down the line. In a perfect world these comments are updated as the world around them changes, but in practice that's seldom done except if the internal code changes as well.

avgcorrection• 3 years ago

HN has such love for that early 20th century writer. So many seemed to have discovered The Fence at about the same time.

ajuc• 3 years ago

This is why comments in the code aren't that useful, and why commit messages are essential.

orbital-decay• 3 years ago

Related concept from software engineering is "accidentally quadratic", which can manifest itself in the most unexpected places when two unrelated things collide.

Both generalize to various forms of causal and failure analysis in systems design.

lambda• 3 years ago

My favorite "accidentally load bearing" artifact that I've found was a misconfigured sudo that would easily allow arbitrary code execution as root (it allowed passwordless sudo for a find command, which could be used with -exec), which a number of important support scripts for the product had been written to use. Load bearing privilege escalation!

squokko• 3 years ago

I've seen this SO many times. "We'll spin up this server that renders thumbnails of images for the UI."... months pass... "Hey why don't we use the thumbnail server to create low-res images for our marketing emails".... months pass... "The UI doesn't show thumbnails anymore so we can tear out the thumbnail server"

gumby• 3 years ago

Evolution does this all the time, which is one of the myriad reasons biology is so hard.

Really good, brief post.

oftenwrong• 3 years ago

The worst part is that it's typically harder to repair the "accidentally load bearing" change than it was to create it in the first place.

JohnMakin2• 3 years ago

I have seen too often overly complicated systems where one small change creates these situations that go unnoticed for far too long and then something breaks in a mystifying and spectacular way. The reaction, generally, is then a fear to make any change to the system at all, regardless of how benign, even if it can't possibly mess something up - because of fear of the "unknown."

IME, having robust alerting and monitoring tools, good rollback plans and procedures/automation should eliminate this fear entirely. If I was afraid to touch anything for fear of breaking it, I'd likely never get anything done.

ninkendo• 3 years ago

having robust alerting and monitoring tools, good rollback plans and procedures/automation should eliminate this fear entirely.

Sure, but that all sounds like stuff that happens after you deploy/release… you really need to catch things sooner than that. Don’t make the user into the one who has to find the breakage, please. No matter how fast you roll back. Test your software thoroughly!

JohnMakin2• 3 years ago

Nothing I said implies the user has to find it. With rolling deployments and blue/green strategies, bad changes don't even have the potential to go live.

dventimihasura6• 3 years ago

I could easily tell why it was there: it was part of a partition for a closet.
Except that over time it had become accidentally load bearing
through other (ill conceived) changes to the structure this stud was now helping hold up the second floor of the house

Evidently, you couldn't easily tell why it was there. Moreover, I'm not persuaded that it accidentally became load bearing. It seems quite plausible that it deliberately became load bearing, for reasons which are ill conceived to you but not to the people who had them.

lmm5• 3 years ago

Evidently, you couldn't easily tell why it was there.

No, they could tell why it was there. It's just that knowing why it was there in the first place doesn't tell you what it's doing now.

dventimihasura6• 3 years ago

"Why it was there" is something that matters to people, plural. Knowing why it was for some people doesn't rule out the possibility that you don't know why it was there for other people.

dventimihasura6• 3 years ago

It is extremely probable that we have overlooked some whole aspect of the question

https://www.reddit.com/r/ProgrammerHumor/comments/q9x1d2/ask...

hinkley10• 3 years ago

Figuring out something's designed purpose can be helpful in evaluating changes, but a risk is that it puts you in a frame of mind where what matters is the role the original builders intended.

One of the biggest challenges I find in refactoring/rearchitecting is getting people to separate why something was done from whether it still needs to exist.

Too many times someone has insisted that a weird piece of code needs to exist because we never would have shipped without it. They treat every piece of the structure as intrinsic, and can't conceive of any part of it being scaffolding, which can now be removed to replace with something more elegant and just as functional.

When you put a doorway through a loadbearing wall, contractors and smart people place a temporary jack to brace the wall until a lintel can be substituted for the missing vertical members. Some developers behave as if the jack is now a permanent fixture, and I have many theories why but don't know which ones are the real reasons.

praptak2• 3 years ago

Let the system go long enough and everything becomes accidentally load bearing. See also "implementation becomes the specification" - people will come to rely on every single undocumented implementation detail regardless of what the official spec says.

That's why it is a good practice to have DiRT or similar exercises. Break things on purpose so that people don't rely on them when they shouldn't.

joshka• 3 years ago

This is a concept I've run into a lot when making changes to complex computer systems. It's useful to look back through the change history, read original design documents, and understand why a component was built the way it was. But you also need to look closely at how the component integrates into the system today, where it can easily have taken on additional roles.

We're probably at a stage where doing this in an automated fashion might be reasonable. The context for why something works a particular way (say in some github repo) is the commit message and change detail, the PR, related issues, related chats in <chat tool of choice>, and then things temporally related to those. Feeding an LLM with the context and generating ADRs for an entire project automatically could be a feasible approach.

Waterluvian• 3 years ago

On the topic of load bearing studs. Is there some way to test for that? How to tell non-destructively how much compression one is under?

duck• 3 years ago

We remodeled our kitchen several years ago. In the old kitchen there was a large beam running across one end, added during some other remodel before we owned the house to add a second floor, but since we wanted to expand on the kitchen this really needed to go. Upon tearing into the ceiling, it was found this beam was ~2 feet to the right of where it should of been to support the wall above. They fixed it and moved the beam into the wall upstairs and it all worked out, but when I asked about the original location the builder basically said: "you had one person that wanted to do the right thing, and one person that didn't care, and quality always ends up with the lowest setting".

iancmceachern• 3 years ago

In mechanical engineering we call this the load path. You want to be sure 1- you know the load path 2- the load path doesn't go where you don't want it to and 3- everything in the load path is strong enough.

A good example of a famous failure if this:

https://en.m.wikipedia.org/wiki/Hyatt_Regency_walkway_collap...

nighthawk454• 3 years ago

Right, so the trick is not to fall into the false-dichotomy trap. Chesterson's Fence tells if you if you don't understand it's purpose, it's probably not safe to remove. That does not imply that if you do understand it's purpose you can now do whatever you want. Chesterson's Fence doesn't tell you anything about when it's safe to remove, only one category of situations where it probably isn't. But that could be an easy misconception.

wduquette• 3 years ago

I think the article interprets Chesterton's Fence too strictly. Chesterton's point was simply that you shouldn't destroy something before making sure that it no longer serves any purpose. The fence was simply an illustration.

Or, to put it another way, figure out what the consequences are before you decide whether you're willing to intend them or not.

Accidentally Load Bearing

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