Debugging k8s cluster connectivity to an outside service

To debug running pods in kubernetes you can follow official guide - https://kubernetes.io/docs/tasks/debug/debug-application/debug-running-pod/ (opens in a new tab).
Following is just a small example in our local context. Let's assume you want to check if you can ping a service from the next-city-library pod.

1. Connect to proper Kubernetes cluster

   In our case, we will connect to tkg-innov-dev. You can follow our Login guide. To verify that you are correctly connected you can run

   kubectl config current-context

   The output should match tkg-innov-dev.

2. Check if your service is running in a pod.

   Run

   kubectl get pods --all-namespaces

   and find your desired pod and copy its name like: next-city-library-app-b868fcd5c-lj6tb.
   If you are running a reasonable *nix shell, you can do

   kubectl get pods --all-namespaces | grep "next-city-library"

   which should help with finding your POD.

3. Create a new debug pod with ubuntu

   Now we will create a new debug pod with ubuntu, and we will attach the container to the pod so we can easily debug it. Run following command to create a new debug POD, which will be a exact copy of your original container (you can read more information in the official docs)

   kubectl debug next-city-library-app-b868fcd5c-lj6to -it --namespace=bratislava-monorepo --image=ubuntu --share-processes --copy-to=next-city-library-app-debug

   Don't forget to update the proper pod and --copy-to to the name you want. Under --copy-to, you will find the running pod. This command will also attach you to newly created POD.

4. Install needed debugging utilities for ubuntu

   Before any installations run, you might need to run

   sudo apt update --yes

   For debugging, you will probably need some networking tools. You can install it with these commands:

   • ping: apt-get install iputils-ping
   • nslookup: apt-get install dnsutils
   • wget: apt install wget
   • curl: apt install curl

5. Clean Up

   After you are done with debugging, please clean up after yourself and delete the pods that you have created and no longer need. For example you can delete our debug pod with following command

   kubectl delete pod next-city-library-app-debug --namespace=bratislava-monorepo