Deployment

Contents

Runs a set of identical pods. It offers scalability, self-healing and rolling updates.
A Deployment automatically creates a ReplicaSet, which then creates a Pod. There is no need to manage ReplicaSets and Pods separately, the Deployment will manage them on our behalf.

Deployment creation

Configuration File

apiVersion: apps/v1
kind: Deployment
metadata:
  name: client-deployment
spec:
  replicas: 3
  selectors:
    matchLabels:
      component: web
  template:
    metadata:
      labels:
        component: web
    spec:
      volumes:
        - name: client-storage
          persistentVolumeClaim:
            claimName: my-volume-claim
      containers:
        - name: client
          image: foo/bar
          ports:
            containerPort: 3000
          volumeMounts:
           - name: client-storage
             mountPath: /foo/bar/baz
          env:
           - name: MY_INTERNAL_HOST
             value: my-cluster-ip-name
           - name: MY_PORT
             value: '1234'
           - name: PASSWORD
             valueFrom:
               secretKeyRef:
                 name: my-secret
                 key: my-key

Kubectl

kubectl create deployment mynginx --image=nginx:1.15-alpine
kubectl create deployment foo --image foo --dry-run=client -o yaml

Rollout

To follow what's going on on rolling update
kubectl rollout status deploy my-deploy

history

kubectl rollout history deploy my-deploy
kubectl rollout history deploy my-deploy --revision=1

undo

kubectl rollout undo deployment my-deploy --to-revision=1

kubectl commands

kubectl scale deploy mynginx --replicas=3

Force pods to re-pull an image without changing the image tag

#33664

Tag built images with a real version number, and specify this version number in the Deployment file

Use an imperative command to update the image version the deployment should use
docker build -t <docker-id>/<image-id>:<version> .
docker push <docker-id>/<image-id>:<version>

kubectl set image <object_type>/<object_name> <container_name> = <new_image_to_use>

kubectl set image deployment/my-deployment my-container=foo/bar:baz-version
kubectl set image deployment mynginx nginx=nginx:1.16-alpine