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Details of the Cloudflare outage on July 2, 2019

(blog.cloudflare.com)
698 points jgrahamc | 2 comments | 12 Jul 19 15:46 UTC | HN request time: 0s | source
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aalleavitch ◴[12 Jul 19 18:26 UTC] No.20423095[source]▶
I’d like to imagine that as long as we live, poorly written regular expressions will continue to be the cause of breaking issues.
replies(2): >>20423929 #>>20424108 #
lmkg ◴[12 Jul 19 19:59 UTC] No.20423929[source]▶
StackOverflow also had an outage a few years ago that was caused by exponential blow-up of a backtracking regular expression.

https://stackstatus.net/post/147710624694/outage-postmortem-...

replies(1): >>20424559 #
1. isaacg ◴[12 Jul 19 21:12 UTC] No.20424559[source]▶
That blow up is quadratic, not exponential: "This is not classic catastrophic backtracking (talk on backtracking) (performance is O(n²), not exponential, in length), but it was enough."
replies(1): >>20427198 #
2. perlgeek ◴[13 Jul 19 09:05 UTC] No.20427198[source]▶
Some years ago I tried to create an exponential time regex in Perl, and only managed a quadratic time one after a bit of experimenting.

But, as you said, quadratic is often already fatal on realistic data.