Kubernetes: ReplicaSets, thesarfo

A ReplicaSet ensures that a specific number of identical Pods are always running. It is an improved version of the older ReplicationController, supporting both equality- and set-based label selectors.

ReplicaSets provide high availability by running multiple instances (replicas) of an application. If one Pod fails, the ReplicaSet automatically creates a replacement. Each replica is created from the same Pod template but has a unique name and IP address, and may be scheduled on different worker nodes.

Example YAML manifest:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: frontend
  labels:
    app: guestbook
    tier: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: guestbook
  template:
    metadata:
      labels:
        app: guestbook
    spec:
      containers:
        - name: php-redis
          image: gcr.io/google_samples/gb-frontend:v3

To create the ReplicaSet:

kubectl create -f redis-rs.yaml

Common commands:

kubectl apply -f redis-rs.yaml
kubectl get replicasets
kubectl get rs
kubectl scale rs frontend --replicas=4
kubectl get rs frontend -o yaml
kubectl get rs frontend -o json
kubectl describe rs frontend
kubectl delete rs frontend