Running applications in containers is easy. Running applications in Kubernetes is, once you know how the system works, relatively easily.
Managing applications is always hard regardless of where and how you run them.
This repo contains a few examples of code, containers and kubernetes artifacts to help to understand the concepts behind kubernetes.
- Ping: a simple http endpoint. You can see the difference of names, labels and selectors, and how they work.
- PingPodRedis: a simple http endpoint that reads & writes to a Redis database. Both containers are in a Pod. State is not maintained.
- Ping-redis: a simple http endpoint that reads & writes to a Redis database. It runs on different Pods using an internal service. State is not maintained either.
Useful Commands
Get cluster info:
kubectl cluster-info
Get pods
kubectl get pods
Get services
kubectl get services
Describe a service: handy when you want to get the public dns
kubectl describe service pingredis
Scaling up & down
kubectl scale --replicas=3 rc pingredis
Check your pods are created
kubectl get pods
Delete one of them to see how a new one is created
kubectl delete pod pingredis-XXXXX
Debugging
kubectl get events
You can get the logs of your containers easily too. If your pod runs more than one container kubectl logs POD_NAME CONTAINER
kubectl logs redis-XXXXX
There are ways of interacting directly with your containers. For example, you can exec a command in your container. Like when doing a docker exec...
kubectl exec redis-XXXXX -- redis-cli get ping
Or you can do port forwarding between your host and your container
kubectl port-forward -p redis-XXXXX 6380:6379