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Release Strategy with Deployment

A Deployment provides declarative updates for Pods and ReplicaSets.

You describe a desired state in a Deployment, and the Deployment Controller changes the actual state to the desired state at a controlled rate. You can define Deployments to create new ReplicaSets, or to remove existing Deployments and adopt all their resources with new Deployments.

Deployment provides three features,

  • Availability: Maintain the number of replicas for a type of service/app. Schedule/delete pods to meet the desired count.
  • Scalability: Updating the replica count, allows you to scale in and out, and its the responsibility of the deployment to provide with that scalability. You could scale manually or use horizontalPodAutoscaler to do it automatically.
  • Update Strategy: Define a release strategy and update the pods accordingly.
cd projects/operation/dev/
cp vote-rs.yaml vote-deploy.yaml

file: file: vote-deploy.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
 name: vote
spec:
 strategy:
   type: RollingUpdate
   rollingUpdate:
     maxSurge: 2
     maxUnavailable: 1
 revisionHistoryLimit: 4
 replicas: 12
 minReadySeconds: 20
 selector:
   matchLabels:
     role: vote
   matchExpressions:
     - {key: version, operator: In, values: [v1, v2, v3, v4, v5]}
 template:
   metadata:
     name: vote
     labels:
       app: python
       role: vote
       version: v1
   spec:
     containers:
       - name: app
         image: c4clouds/vote:v1
         resources:
           requests:
             memory: "64Mi"
             cpu: "50m"
           limits:
             memory: "128Mi"
             cpu: "250m"

To create Deployment execute the below command

kubectl apply -f vote-deploy.yaml

Rolling out a new version

Now, update the deployment spec to use a new version of the image.

file: vote-deploy.yaml

template:
  metadata:
    labels:
      version: v2   
  spec:
    containers:
      - name: app
        image: c4clouds/vote:v2
kubectl apply -f vote-deploy.yaml

kubectl rollout status deployment/vote

Breaking a Rollout

file: vote-deploy.yaml

spec:
  containers:
    - name: app
      image: c4clouds/vote:fake-version
kubectl apply -f vote-deploy.yaml

kubectl rollout status

Undo and Rollback

kubectl rollout history deploy/vote

kubectl rollout history deploy/vote --revision=xx

kubectl rollout undo deploy/vote --to-revision=2