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Interns with toasters: how I taught people about load balancers

rachelbythebay.com

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Re: Interns with toasters: how I taught people about load balancers

#61

Post by mrmanner »

spydum wrote: post #49
Rainymood wrote: post #41

Earlier quoted context omitted.

So basically she's using HN audience as a marketing blog and people are eating it up?

Marketing? What pray tell is she selling? If this had been some post about lessons learned about a the latest whizbang JS framework people wouldn't have had a second thought. I've read plenty of her posts and have sympathized, as being a long time sysadmin and learning the exact same lessons. She indeed does have a story telling skill which is sorely needed: ops people tend to suck at effectively sharing knowledge -…

> I don't understand why there is criticism?

If I were to be cynical, I'd say it's because a woman writing on information technology. Or because someone is writing about information technology without it being strict and to the point and boring to everyone that doesn't have a geeky interest in that specific piece of technology. But most likely the former.

Re: Interns with toasters: how I taught people about load balancers

#62

Post by MaxGabriel »

snovv_crash wrote: post #39

This reminds me strongly of another system of distribution, which suffers from the same effect: differential gearboxes in cars. Since the torque to all the wheels is equal, if one wheel slips it very quickly takes all of the power of the engine, since power = rotational velocity * torque. Only if the speeds are similar is the allocation of power to the wheels similar. In cars, the solution is to make sure that the po…

If I remember the movie My avoiding Vinnie correctly, is this called Positraction? Marissa Tomei’s character says positraction prevents being “stuck in the mud”, where “one tire spins, the other tire does nuthin’”

Re: Interns with toasters: how I taught people about load balancers

#63

Post by mrmanner »

andrew_wc_brown wrote: post #32

Based on how verbose this article is I think maybe her original article was misunderstood because it was a chore to sort out the junk from the content just like this one. Too much flourishing, poor pacing

Just the right amount of flourishing for a lazy Sunday :)

Re: Interns with toasters: how I taught people about load balancers

#64

Post by notyourwork »

pulkitsh1234 wrote: post #23

Maybe some people dismissed her problem as 'impossible' because she didn't inform what kind of load balancing technique was the load balancer using? I suspect what happened is that they didn't understand the problem, and so resorted to ineffective means to steer the attention away from their own inadequacies. ^ This statement is kinda harsh.

I think it would be better phrased as suggesting they thought they understood but really didn’t understand the problem and therefore made a preemptive conclusion.

Re: Interns with toasters: how I taught people about load balancers

#65

Post by wging »

lazyant wrote: post #52

Great "teaching by showing" example but I don't get the initial technical scenario; you have sophisticated (ie, not RR / random) load balancers that keep track of queues in web servers, so they have to get some information back from them (when job was completed, from HTTP response for ex), but somehow don't react to 500 errors? seems like badly configured LBs. Still scenario can be used as teaching or interview quest…

Suppose that a machine succeeds fast, not fails fast. Say a machine's job is to run N things on its input, and the identities of these N things are picked up from configuration somewhere. One machine gets a corrupted config somehow, and has only 1 thing to run. The others are running 10 things. So one machine is (barring framework/networking/etc. overhead) 10x faster than the rest, and it thinks it's doing fine. Now even if your mind is stuck on HTTP, you have to think about the same problem but with 200 response codes. Still a non-issue?

And what if the responses are opaque to the LB? TCP-level load balancing, maybe? There are reasons you might choose that. Or maybe the protocol you use is not HTTP-based and you don't have a way to teach your LB about it.

Re: Interns with toasters: how I taught people about load balancers

#66

Post by jdietrich »

MaxGabriel wrote: post #62
snovv_crash wrote: post #39

This reminds me strongly of another system of distribution, which suffers from the same effect: differential gearboxes in cars. Since the torque to all the wheels is equal, if one wheel slips it very quickly takes all of the power of the engine, since power = rotational velocity * torque. Only if the speeds are similar is the allocation of power to the wheels similar. In cars, the solution is to make sure that the po…

If I remember the movie My avoiding Vinnie correctly, is this called Positraction? Marissa Tomei’s character says positraction prevents being “stuck in the mud”, where “one tire spins, the other tire does nuthin’”

Positraction was a brand name used by GM for some limited slip differential systems.

Re: Interns with toasters: how I taught people about load balancers

#67

Post by [deleted] »

foota wrote: post #26
grosjona wrote: post #22

That's why I like random load balancing. If each machine is powerful enough and can handle a few thousand users then the distribution averages out. Smart load balancers are only really necessary if you have inefficient servers that can't handle more than 100 connections per second and they're difficult to get right. If you toss a coin 10 times, you're much more likely to get >=80% heads than if you were to toss that…

This is true, but if you have a tighter tolerance on how much load each machine needs to be able to handle then you may be able to waste less resources.

[deleted]

Re: Interns with toasters: how I taught people about load balancers

#68

Post by rachelbythebay »

hightowk wrote: post #51

>and so on down the line until everyone had bread. At various points, a toaster would finish and would pop up. ... I'd notice that they were done and would run over to give them more toast. You'd give them more bread, not toast. Toast is already processed bread :).

Ah! Correct you are. Fixed. Thanks!

Re: Interns with toasters: how I taught people about load balancers

#69

Post by jdietrich »

BillinghamJ wrote: post #12
rajacombinator wrote: post #8

Earlier quoted context omitted.

What kind of college teaches about load balancers?

If they’re not teaching about the most basic principles of building scalable systems, what is the point of doing a degree, or hiring people who have done a degree?

Rightly or wrongly, universities are not vocational colleges. They exist to teach the theoretical principles of a field, not the practical skills of a particular job.

Re: Interns with toasters: how I taught people about load balancers

#70

Post by indigodaddy »

vasco wrote: post #4

And that's why you always set health checks on servers behind a load balancer that should take bad ones out as soon as possible. You then get another interesting problem, which is if the server is only spitting errors when serving requests, it'll then be marked healthy again and forever toggle between healthy and unhealthy. But that you can also solve.

If you are doing an L7 http health check, then you should be able to validate a specific URI's expected successful/healty response.
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