So let’s get started!!
What is Replication Controller?
Replication Controller make sure that at least n number of pods are running in our Kubernetes cluster, where n is the number of of replicas we define.
So Replication Controller maintains the desired number of Pods always.
Link between RC and Pod
How does RCA knows which Pod to manage? – It happens via a keyword label and selectors.
In the RC we define selectors which basically points to the label defined in Pod.
So let’s write manifest.yml
Create a file replicationController.yml
apiVersion: v1 kind: ReplicationController metadata: name: rcontroller-nginx spec: replicas: 3 selector: app: my-nginx-app template: metadata: name: nginx-pod labels: app: my-nginx-app spec: containers: - name: nginx-container image: nginx
Now deploy the above RC using
kubectl apply -f replicationController.yml
let’s check our pods using
kubectl get pods to verify the same!!
Now let’s say we want to scale our pods from 3 to 5
kubectl scale rc rcontroller-nginx --replicas 5
Verify the pods using kubectl get pods.
Let’s delete one pod and check if any new pods get created.
kubectl delete pod <podname>
You might be seeing one new Pod being created and it’s been 7 seconds it’s up.
This all how you can get started with Replication Controller, do post queries in comment section if you have one.!!!!