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The 32-Bit Dog Ate 16 Million Kids' CS Homework (code.org)
"Any student progress from 9:19 to 10:33 a.m. on Friday was not saved..." explained the embarrassed CTO of the educational non-profit Code.org, "and unfortunately cannot be recovered."
Slashdot reader theodp writes:
Code.org CTO Jeremy Stone gave the kids an impromptu lesson on the powers of two with his explanation of why The Cloud ate their homework. "The way we store student coding activity is in a table that until today had a 32-bit index... The database table could only store 4 billion rows of coding activity information [and] we didn't realize we were running up to the limit, and the table got full. We have now made a new student activity table that is storing progress by students. With the new table, we are switching to a 64-bit index which will hold up to 18 quintillion rows of information.
The issue also took the site offline, temporarily making the work of 16 million K-12 students who have used the nonprofit's Code Studio disappear. "On the plus side, this new table will be able to store student coding information for millions of years," explains the site's CTO. But besides Friday's missing saves, "On the down side, until we've moved everything over to the new table, some students' code from before today may temporarily not appear, so please be patient with us as we fix it."
The issue also took the site offline, temporarily making the work of 16 million K-12 students who have used the nonprofit's Code Studio disappear. "On the plus side, this new table will be able to store student coding information for millions of years," explains the site's CTO. But besides Friday's missing saves, "On the down side, until we've moved everything over to the new table, some students' code from before today may temporarily not appear, so please be patient with us as we fix it."
Seriously, was not a single developer or architect from Code.org around when Slashdot overflowed its 24-bit index? I know it has been a few years now, but I'm sure there are folks here who remember threading breaking and all other sorts of problems when it happened. Remember: https://slashdot.org/story/06/11/09/1534204/slashdot-posting-bug-infuriates-haggard-admins
Granted, that was Slashdot, and while annoying, it was hardly the end of the world This problem with Code.org clearly reinforces "cloud bad" to people who are already fearful of putting their data in the cloud.
I am guessing that Code.org didn't bother tracking things like how to close to various limits they were getting, but I bet that they are now. In any event, when this happened to Slashdot 10+ years ago, I suppose you could argue that we weren't as advanced. In 2016-2017 there is no excuse for such a critical architectural flaw. To me, it completely undermines my confidence in their entire platform. What other time bombs are ticking under the surface there?
For a lot of things, 32 bit is overkill, but you don't see people storing 24 bit numbers. This is a fundamental problem with premature optimization. You should always use the largest precise integer available unless you have a compelling, evidence-based reason not to. The onus should be on the 32bit users to demonstrate their choice is better.