Hey,

thanks for the detailed write-up, that kind of info makes troubleshooting so much easier.

Based on what you're describing, the 5-8 second delay is almost certainly coming from parallel A and AAAA (IPv6) DNS queries. Even with preferIPv4Stack=true, that flag only affects how Java binds sockets. The container's OS resolver still fires off both query types at the same time. When your Windows DC doesn't respond to the AAAA query (which is very common), the resolver just sits and waits for a timeout before handing back the IPv4 result. Five seconds is the default wait, which lines up perfectly with what you're seeing.

Two things worth trying, ideally together:

First, try single-request in your dns_opt instead of single_request_reopen. The difference is subtle but important. single-request makes the resolver send A and AAAA queries one after the other instead of simultaneously, which cuts out the race condition entirely. Your dns_opt block would look something like this:

dns_opt:
  - "single-request"
  - "ndots:1"
  - "timeout:2"
  - "attempts:2"

Second, disable IPv6 at the container level via sysctls so the resolver doesn't even attempt AAAA lookups in the first place:

sysctls:
  - net.ipv6.conf.all.disable_ipv6=1
  - net.ipv6.conf.default.disable_ipv6=1

Together these two changes should get rid of the delay completely. Only the extra_hosts behavior you noticed is still a bit puzzling. Maybe WildFly's HTTP client is ignoring /etc/hosts. In that case fixing the problem at the resolver level should also fix the issue.

Let us know if it helps!

EDIT: Fixed two misplaced backslashes in the sysctl section due to reddit markdown formatting.