In the aftermath of this leap second, Cloudflare experienced an outage and blogged about it. It seems the root cause was code that expected a monotonically ascending value for seconds, but the additional second was handled (by the Go library used) by letting time go backwards one second, which led to negative durations for some events, which finally were not handled gracefully.

I think this would not have been a problem for Cloudflare if they too had stretched the duration of a second, at least for their machines running RRDNS. Of course, this is literally Monday quarterbacking as I wasn't part of the decision process there. Also, knowing and understanding how time and durations are used within your code is not an easy thing if you don't explicitly analyze your code for the usage of both.

In reply to Re^4: Leap second coming up. Check your date handling code (Cloudflare DNS outage) by Corion
in thread Leap second coming up. Check your date handling code by 1nickt

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