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Cloudflare outage on December 5, 2025

blog.cloudflare.com

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Re: Cloudflare outage on December 5, 2025

#21

My understanding, paraphrased: "In order to gradually roll out one change, we had to globally push a different configuration change, which broke everything at once". But a more important takeaway: > This type of code error is prevented by languages with strong type systems

That's a bizarre takeaway for them to suggest, when they had exactly the same kind of bug with Rust like three weeks ago. (In both cases they had code implicitly expecting results to be available. When the results weren't available, they terminated processing of the request with an exception-like mechanism. And then they had the upstream services fail closed, despite the failing requests being to optional sidecars rather than on the critical query path.)

Re: Cloudflare outage on December 5, 2025

#22
post #3

> Customers that did not have the configuration above applied were not impacted. Customer traffic served by our China network was also not impacted. Interesting.

They kinda buried the lede there, 28% failure rate for 100% of customers isn't the same as 100% failure rate for 28% of customers

Re: Cloudflare outage on December 5, 2025

#24
Ironically, this time around the issue was in the proxy they're going to phase out (and replace with the Rust one).

I truly believe they're really going to make resilience their #1 priority now, and acknowledging the release process errors that they didn't acknowledge for a while (according to other HN comments) is the first step towards this.

HugOps. Although bad for reputation, I think these incidents will help them shape (and prioritize!) resilience efforts more than ever.

At the same time, I can't think of a company more transparent than CloudFlare when it comes to these kind of things. I also understand the urgency behind this change: CloudFlare acted (too) fast to mitigate the React vulnerability and this is the result.

Say what you want, but I'd prefer to trust CloudFlare who admits and act upon their fuckups, rather than trying to cover them up or downplaying them like some other major cloud providers.

@eastdakota: ignore the negative comments here, transparency is a very good strategy and this article shows a good plan to avoid further problems

Re: Cloudflare outage on December 5, 2025

#28
> This is a straightforward error in the code, which had existed undetected for many years. This type of code error is prevented by languages with strong type systems. In our replacement for this code in our new FL2 proxy, which is written in Rust, the error did not occur.

Cloudflare deployed code that was literally never tested, not even once, neither manually nor by unit test, otherwise the straightforward error would have been detected immediately, and their implied solution seems to be not testing their code when written, or even adding 100% code coverage after the fact, but rather relying on a programming language to bail them out and cover up their failure to test.

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