Cloudflare 這次閏秒炸掉：「How and why the leap second affected Cloudflare DNS」，影響範圍包括了 DNS query 與 HTTP request：
At peak approximately 0.2% of DNS queries to Cloudflare were affected and less than 1% of all HTTP requests to Cloudflare encountered an error.
主要的原因在於 Go 的 time.Now() 不保證遞增：
RRDNS is written in Go and uses Go’s time.Now() function to get the time. Unfortunately, this function does not guarantee monotonicity. Go currently doesn’t offer a monotonic time source (see issue 12914 for discussion).
修正的方式是針對時間回朔時處理：
In this patch we allowed RRDNS to forget about current upstream performance, and let it normalize again if time skipped backwards.
應該是因為 Cloudflare 這段程式還沒遇過 leap second 造成的...