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Hello,
Our Kubernetes cluster is experiencing DNS resolution failures. CoreDNS logs show "i/o timeout" errors when attempting to reach 168.63.129.16:53.
This issue began approximately two days ago. Prior to this, DNS resolution was functioning correctly.
Interestingly, we have found that restarting the Kubernetes cluster temporarily resolves the issue, but it reappears after a period of time. This suggests a potential underlying network state issue or a service that degrades over time.
We have not configured any custom firewalls or DNS settings, with the exception of an external DNS record forwarding specificURL.com to the cluster.
Thank you for your help.
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Hi Severin Hersche,
Thank You for reaching out to Microsoft Q&A forum.
Can you please confirm where does the DNS resolution fail? Pod, Node or Both pods and nodes.
and also, can you please share CoreDNS logging error messages.
Verify once if the CoreDNS pods are running:
kubectl get pods -n kube-system
Check once whether the CoreDNS pods are overused:
kubectl top pods -n kube-system
If the information is helpful, please click on "Upvote"
If you have any queries, please do let us know by sharing in detail errors/logs, we will help you.
Thank you for your comment. As far as I understand it it is failing on both levels pod and node. Two coredns pods are up and runnung. But I had a restart on the coredns-autoscaler pod - not sure if this is relevant. There are a lot of errors please find one example:
[ERROR] plugin/errors: 2 global.handler.control.monitor.azure.com. A: read udp 10.244.1.78:46160->168.63.129.16:53: i/o timeout
[ERROR] plugin/errors: 2 global.handler.control.monitor.azure.com. A: read udp 10.244.1.78:54988->168.63.129.16:53: i/o timeout
This is the output of the kubectl top pods:
NAME CPU(cores) MEMORY(bytes)
coredns- 2m 38Mi
There is this error in the autoscaler pod logs - not sure if this is relevant:
E0310 08:14:37.627767 1 autoscaler_server.go:108] Error while getting cluster status: context deadline exceeded
E0310 08:14:47.627960 1 autoscaler_server.go:108] Error while getting cluster status: context deadline exceeded