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Post Mortem: A single whitespace character

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Re: Post Mortem: A single whitespace character

#71

Post by hyperpape »

jrochkind1 wrote: post #7

This very example -- requests were technically illegal all the time without devs realizing, but something in the stack changed to start rejecting them -- demonstrates the fallacy of the "be liberal in what you accept, strict in what you issue" principal. If all the web servers involved had been strict in rejecting the illegal request from the start, they would have noticed the bug in development before deploying to f…

I recall reading that Postel's law did not mean "accept input that flagrantly ignores the standard", but merely wherever the standard might be read differently, accept all conceivable interpretations of the standard. Unfortunately, I can't remember for sure where I read this, or how authoritative it was.

Postel's original formulation is not written in an essay, but an RFC, and does not elaborate on what he meant: https://tools.ietf.org/html/rfc761

Here's one discussion that suggests this interpretation, without precisely ascribing it to Postel: http://cacm.acm.org/magazines/2011/8/114933-the-robustness-p...

Re: Post Mortem: A single whitespace character

#73

Post by rubiquity »

pilif wrote: post #50

Likely "Cowboy" is a transparent proxy added by your mobile service provider. I had a similar thing happening a year ago when the mobile provider used by most of our barcode scanners decided to add a transparent proxy into the loop (without telling anybody). The solution for this problem: Use SSL. I mean: There are already many good reasons to use SSL, but whenever you need to send any kind of mission critical data o…

Cowboy is the name of an Erlang web server and Heroku uses Erlang for their routing. I imagine the reason Cowboy is showing up is due to Heroku's routing layer.

Re: Post Mortem: A single whitespace character

#74

Post by hlieberman »

cleanCodeAtWork wrote: post #63

Are there any languages out there that handle scale and many connections like Erlang does, but with an easier to swallow syntax?

Erlang. The syntax really isn't that bad, once you get over the initial shock. In all honesty, grasping that the variables are immutable and how you need to change your thinking is much more difficult than the syntax itself.

Re: Post Mortem: A single whitespace character

#76

Post by krakensden »

Danieru wrote: post #28

That series of strcat's caught my eye as bad practice. Fine in this case since the destination string is short but horrible in general. Every single one of those calls needs to iterate over the entire existing string to find the string size. The code could be much cleaner with a small macro hiding the incrementation and the casts.

Yeah- implicit concatenation + snprintf seems like the way to go. Although you'd have to calculate a length, I suspect avoiding that is the primary virtue of this approach.

Re: Post Mortem: A single whitespace character

#77

Post by srtjstjsj »

lostcolony wrote: post #31
akerl_ wrote: post #19

Earlier quoted context omitted.

This doesn't demonstrate a fallacy in "be liberal in what you accept" any more than closed source software demonstrates fallacies in Linus's Law. The problem wasn't liberal acceptance, it was that liberal acceptance ended when Cowboy was added to the mix. Strict acceptance would have shown the error earlier, but continued liberal acceptance would have allowed continued functionality.

You mean so long as everyone standardizes around a non-standard, rather than the actual specifications of the standard, it'll work? I think I prefer just adhering to the standard in the first place.

That's what "strict in what you issue" means

Re: Post Mortem: A single whitespace character

#78

Post by srtjstjsj »

mikeash wrote: post #65
Danieru wrote: post #28

That series of strcat's caught my eye as bad practice. Fine in this case since the destination string is short but horrible in general. Every single one of those calls needs to iterate over the entire existing string to find the string size. The code could be much cleaner with a small macro hiding the incrementation and the casts.

A sufficiently smart compiler could optimize a string of strcat calls to remove the redundant length finding. I have no idea if real compilers actually would....

Java does, for the "+" operator.

Re: Post Mortem: A single whitespace character

#79

Post by kstrauser »

If this were my team, I would be unsettled by the fact that we never caught it in testing. Did no one write tests to exercise this part of the app - the one where we're handcrafting HTTP requests?

Objectively, you need to write more tests. At the minimum, this bug should have a regression test so that it can never accidentally happen again (say when a dev merges an old branch in for whatever reason).

Re: Post Mortem: A single whitespace character

#80

Post by angersock »

goleksiak wrote: post #69
pilif wrote: post #50

Likely "Cowboy" is a transparent proxy added by your mobile service provider. I had a similar thing happening a year ago when the mobile provider used by most of our barcode scanners decided to add a transparent proxy into the loop (without telling anybody). The solution for this problem: Use SSL. I mean: There are already many good reasons to use SSL, but whenever you need to send any kind of mission critical data o…

We would really like to use HTTPS but it's not supported by the Arduino chipset as I understand it. Though I'm not the hardware guy here at eatabit...

Why don't you guys just use a Beaglebone Black ($50), M2M cape (http://www.yantrr.com/products/m2m-cape-for-beaglebone), and a thermal printer (https://www.sparkfun.com/products/10438). BOM for that, plus project enclosure, is like $200. That's also just after a bit of quick googling...there's bound to be a much cheaper solution.

What's your price point for hardware?

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