您是否会因在 CNAME 或 A rec 中输入错误而意外造成大量停机？

Question

Let's say I need to change the CNAME for my subdomain test.mysite.com. I want it to go to a load balancer endpoint 'aws-my-endpoint.com'.

But in creating the CNAME, I type it wrong. eg 'aw-my-endpoint.com'

Since it's possible that a client can cache DNS for up to 48hrs (despite what the TTL setting is), could this cause test.mysite.com to be down for 48hours? Even though I immediately fix the CNAME after noticing the typo?

Answer 1

Yes. I've seen with ELB to ALB transitions where clients still hit the ELB, sometimes for days. Most traffic however, usually take a few minutes to port over.

But with a non-existent target (like a typo in your case), there's a chance it would be faster since clients typically wouldn't cache a failed response. The resolvers may cache but they'd respect the TTL specified on the record. There's more on this behavior on this thread