domain could not be resolved (110: Operation timed out)

[zffocussss]

Hi team:
I am running openresty as a pod in k8s,but when some http requests are sent by lua-resty-http module,there are so many dns issues.
I use tcpdump to catch the network traffic between my openresty pods and coredns pods which is responsible for dns resolution.
the process is ok in my view.
can some one help me about it?

nginx version: openresty/1.21.4.1
lua-resty-http version: 0.17.1-0
k8s version: 1.26 Alibaba Cloud k8s service

error logs

• The exact version of the related software, including but not limited to the OpenResty version
  (if any), the NGINX core version, the ngx_lua module version(via openresty -V or nginx -V),
  and your operating system version(via uname -a).

nginx version: openresty/1.21.4.1
built by gcc 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
built with OpenSSL 1.1.1t 7 Feb 2023

[lijunlong]

If the problem happens again, you can try to resolve the domain with dig in the openresty pod.
you can use netstat to check the fd of the DNS query socket. And then use strace to see if there are response.