• How to verify that an application is working as expected? One way is to use tooling such as busybox.
  • BusyBox –> Swiss Army Knife of Embedded Linux.
    • Binary that contains many UNIX tools such as awk, date, wget and whoami
    • Good tool for debugging and troubleshooting issues.
  • We will use a deployment yaml file to create the BusyBox pod.
  • This will only be deployed in the default namespace. It will run only 1 replica. 
    kubectl apply -f busybox.yml
  • Then run the following to check that the pod is running: kubectl get pods
    • If you don’t specify -n, kubectl will assume you want the default namespace.
  • Want to use BusyBox, for an HTTP GET request to the application. Need to know the IP address of the pods, in order to accomplish that.
  • Then we run: 
    kubectl get pods -n development -o wide
  • -o wide shows additional information about the pods, including their IP addresses inside the Kubernetes cluster.
  • Need to get inside the busybox pod, so we can use the wget tool to make an HTTP request.
  • Use the kubectl command, exec
  • busybox-74b7c48b46-wzhnt
  • To exec into the pod, we use: 
    kubectl exec -it busybox-74b7c48b46-wzhnt -- /bin/sh
  • -it means we want to access the pod and use an interactive terminal.
  • Then we need to specify the shell with:
    • In this case, the /bin/sh uses the Executable Shell, but we can use any Shell that we like.
  • If you run the wget command inside a container, you will receive the following: 
    Connecting to 10.244.0.7 (10.244.0.7:80)
wget: can't connect to remote host (10.244.0.7): Connection refused
/ #
  • Remember in the deployment.yml file, the pod was set up to use the port 3000.
  • wget 10.244.0.7:3000
  • You will then see pod info like so: 
    Connecting to 10.244.0.7:3000 (10.244.0.7:3000)
saving to 'index.html'
index.html           100% |******************************************************************************************************************************************************|   103  0:00:00 ETA
'index.html' saved
/ # cat index.html 
{"pod_name":"pod-info-deployment-7587d5cc86-lkccq","pod_namespace":"development","pod_ip":"10.244.0.7"}/ #
  • Now we have verified that the application is running.
  • How to check that an application is working and if the cluster is not connected to the Internet. Use BusyBox and then run the wget request.

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