[loevborg]

I don't know about Golang but I swear I've seen this before as well - clients holding on to an old IP address without ever re-resolving the domain name. It makes me wary of using DNS for load balancing or blue-green deployments. I feel like I can't trust DNS clients.

[wink]

It's been 8-10 years but when I was serving tracking pixels we were astonished how long we still got requests from residential IPs for whole hostnames we had deprecated. That means I would not trust DNS caching anyway. I'm not talking days here, but months, with a TTL set to mere days.

[ignoramous]

Some reasons to connect to the same IP: TCP Fast Open, TLS session resumption, connection pools, residual censorship.

[fragmede]

The other reason: you have an open TCP socket that you're actively using. Unless you finish with that connection or it breaks, why would you re-resolve it when you're not running connect() a second time? The failure mode we noticed most when looking into why clients weren't following DNS changes isn't that they were long lived connections, like a server copying a large file or streaming logs. Which isn't unusual if you think about it, just not a short lived web browser or curl-esque connection.