How to add dns entry in a remote machine based on the assigned hostname and worker node ip in kubernetes - kubernetes

Question

I have a kubernetes cluster which has two worker nodes. Each worker node will have one pod. I have configured in helm chart, the hostname of those pods will be pod-0.test.com and pod-1.test.com. I have pointed the coredns to forward any DNS requests that matches ".com" domain to a remote machine where unbound is running which will take of actual DNS resolution.
.com:53 {
errors
cache 30
forward . <remote machine IP>
}
Let's take worker-0 node IP is 10.x.y.z and worker-1 node IP is 10.a.b.c and Let's say, pod-0.test.com sits in worker-0 and pod-1.test.com sits in worker-1. I have DNS entries configured in unbound of remote machine which will resolve as below:
pod-0.test.com -> 10.x.y.z
pod-1.test.com -> 10.a.b.c
When I uninstall pods and reinstall it, there are chances where pod-0.test.com will sit in worker-1 and pod-1.test.com will sit in worker-0. So if the pods gets swapped between worker nodes, I need to again change the unbound configuration and restart unbound. I will come to know which pod sits in which worker node only after pod gets installed but I need to have proper DNS entries in the remote machine configured in prior to this otherwise pods will gets restart when the pod hostname is resolved to wrong IP.
So what I am looking for is to overcome this issue somehow by automating to have proper DNS entries configured according to the worker node IP where the pod sits in. Is there any way to achieve this? Or Is there a possibility that pod or coredns will itself add proper DNS entry in the remote machine (which is configured in forward directive of coredns) before it is coming up like pre-install step? I need to have this pod hostname to worker node IP resolution should happen properly in both remote machine as well as inside the pods.
It would be really helpful if someone has an approach to handle this issue. Thanks in advance!

Answer 1

there is a work around for this issue you can use node selectors for deploying your pods on the same node. If you don’t want to do it in this way, if you are implementing this via a pipeline you can add a few steps to your pipeline for making the entries the flow goes as below.
Trigger CI/CD pipeline → Pod getting deployed → execute kubectl command for getting pods on each node → ssh into the remote machine give sudo privileges if required & change the required config files.
Use the below command to get details of pods running on a particular node
kubectl get pods --all-namespaces -o wide --field-selector spec.nodeName=<node>

Answer 2

Have you tried using Node Affinity. You can schedule a given pod always to the same Node using node labels. Simply you can use kubernetes.io/hostname label key to select the Node as below:
First Pod
apiVersion: v1
kind: Pod
metadata:
name: pod-0
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: kubernetes.io/hostname
operator: In
values:
- worker1
hostname: pod-0.test.com
containers:
...
...
Second Pod
apiVersion: v1
kind: Pod
metadata:
name: pod-1
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: kubernetes.io/hostname
operator: In
values:
- worker2
hostname: pod-1.test.com
containers:
...
...