Kubernetes – Deployments

• Deployment is one of the most used object by DevOps engineers.
• Most of the DevOps work is involved around making deployments and making regular changes to the application code.
• Deployments are used for Upgrading apps/pod images, rollback, and performing these changes gracefully.
• A Deployment controller provides declarative updates for Pods and Replica sets.
• Deployment manages the replica sets to manage the number of pods.

Deployment Definition File – Sample 1

## Deploy 3 pods of name http-frontend, of image httpd on alpine 2.4
---
apiVersion: apps/v1

## Note the Kind type here
kind: Deployment
metadata:
  name: httpd-frontend
spec:
  selector:

    ## Note: ReplicaSets will not have the "matchLabels"
    matchLabels:
      name: httpd-frontend
  template:
    metadata:
      labels:
        name: httpd-frontend
    spec:
      containers:
      - image: httpd:2.4-alpine
        name: httpd-frontend
  replicas: 3

Deployment Definition File – Sample 2

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-nginx-server
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-servers
        image: nginx:latest
        resources:
          limits:
            memory: "128Mi"
            cpu: "500m"
        ports:
        - containerPort: 80