Kubernetes Replication Controller
A replication controller (RC) in kubernetes is a supervisor for long-running pods. Kubernetes RC helps in launching and running number of pods with specified number of replicas to help in failure.
Example of ReplicationController
This example ReplicationController config runs four copies of the nginx web server with name replication.yaml
apiVersion: v1
kind: ReplicationController
metadata:
name: nginx
spec:
replicas: 4
selector:
app: nginx
template:
metadata:
name: nginx
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 80
Run the example job by downloading the example file and then run this below command:
kubectl apply -f replication.yaml
Check on the status of the ReplicationController using this below command:
kubectl describe replicationcontrollers/nginx
Name: nginx
Namespace: default
Selector: app=nginx
Labels: app=nginx
Annotations: <none>
Replicas: 4 current / 4 desired
Pods Status: 0 Running / 4 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: app=nginx
Containers:
nginx:
Image: nginx
Port: 80/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
Events:
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
--------- -------- ----- ---- ------------- ---- ------ -------
20s 20s 1 {replication-controller } Normal SuccessfulCreate Created pod: nginx-qrm3m
20s 20s 1 {replication-controller } Normal SuccessfulCreate Created pod: nginx-3ntk0
20s 20s 1 {replication-controller } Normal SuccessfulCreate Created pod: nginx-4ok8v
20s 20s 1 {replication-controller } Normal SuccessfulCreate Created pod: nginx-4ok8v