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Getaddrinfo does not resolve in some kubernetes pod on some hosts

ma flag

I have a pod where getaddrinfo cannot resolve the address to a Kubernetes Service in the same namespace but can connect to the service if I use the IP address instead. Using tcpdump, I can confirm that it does not send DNS queries to nodelocaldns or to coredns. Manually adding the address to /etc/hosts does not resolve the issue. The image of the pod is a derivative of https://github.com/jupyter/docker-stacks/tree/master/datascience-notebook and runs start-singleuser.sh as entry point.

If I create a pod on the same machine but only run sleep as entry point, everything works. This issue also occurs in some of the newer machines (installed around 2 years after the cluster was initially set up).

Any ideas how to fix or troubleshoot this extremely puzzling issue?

Jakub Siemaszko avatar
jp flag
What Kubernetes version are you using? How have you deployed it? Could you provide a .yaml file of your pod?
Wytrzymały Wiktor avatar
it flag
Hello @ChristianAlis. Any updates?
ma flag
It's running kubernetes 1.19 installed by kubespray 2.15.1. The cluster has been running for 3 years now so there might be changes that were not migrated properly although I used the defaults mostly. I tried running `start-singleuser.sh` on the working pod but the dns resolution didn't fail afterwards.
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