Posted on Nov 15, 2023 • Edited on Nov 22, 2023

Kubernetes Deployment

Deployment

A K8s Deployment is a declarative configuration in a .yaml or .json file to define the desired state of an containerized piece of code.

Create a basic deployment.yaml

kubectl create deploy your-deployment --image=your-image -oyaml --dry-run=client > deploy.yaml

Modify as needed, for example you can add livenessProbes
run kubectl apply -f=deploy.yaml
check run kubectl describe deploy

Deployment Configuration Status

kubectl get deployments
kubectl describe deployment yourdeploymentname

availableReplicas

indicates how many were configured by the ReplicaSet. This would be compared to the later value of #### readyReplicas
which would be used to determine if all replicas have been fully generated and without error. #### observedGeneration
shows how often the deployment has been updated. This information can be used to understand the rollout and rollback situation of the deployment.

Scaling and Rolling Updates

kubectl scale deploy/dev-web --replicas=4

Rolling Update

If you want to modify non-immutable values, you can change them in an editor.
This triggers a rolling update of the deployment. While the deployment would show an older age, a review of the Pods would show a recent update and older version of the web server application deployed.

kubectl edit deployment yourdeployment

containers: - image: geile-app:1.8 #<<---Change version number imagePullPolicy: IfNotPresent name: dev-geile-app

This will update gradually replacing old pods with new ones to ensure continuous availability of the service.
It is the default update method

strategy: type: RollingUpdate rollingUpdate: maxUnavailable: 1 maxSurge: 1

Canary Rollout

A new version of the application is deployed to a small percentage of the pods or replicas in the Kubernetes cluster. This can be achieved using a Deployment resource with specific strategies and configurations.

apiVersion: apps/v1 kind: Deployment metadata: name: your-app spec: replicas: 5 strategy: type: RollingUpdate rollingUpdate: maxSurge: 25% <--- incremental increase in the number of pods running the canary version. maxUnavailable: 0 template: metadata: labels: app: your-app spec: containers: - name: your-app image: your-registry/your-app:canary

Blue- Green Deployment

In a Blue-Green Deployment, two identical environments, typically referred to as "Blue" and "Green," are maintained: - one for the current production version (Blue) and

one for the new version being deployed (Green).

The deployment process involves switching the traffic from the Blue environment to the Green environment once the new version is considered ready for production.

# blue-deployment.yaml apiVersion: apps/v1 kind: Deployment metadata: name: blue-deployment spec: replicas: 3 selector: matchLabels: app: your-app color: blue template: metadata: labels: app: your-app color: blue spec: containers: - name: your-app image: registry/your-app:blue ports: - containerPort: 80 # green-deployment.yaml apiVersion: apps/v1 kind: Deployment metadata: name: green-deployment spec: replicas: 0 # Keeping replicas at 0 initially selector: matchLabels: app: your-app color: green template: metadata: labels: app: your-app color: green spec: containers: - name: your-app image: registry/your-app:green ports: - containerPort: 80 # service.yaml apiVersion: v1 kind: Service metadata: name: your-app-service spec: selector: app: your-app ports: - protocol: TCP port: 80 targetPort: 80

and then deploy the first
kubectl apply -f blue-deployment.yaml
once validated and deploy the other version
kubectl apply -f green-deployment.yaml