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Deployment

Upgrade your apps (pod images).

Rollbacks if something goes wrong.

A deployment controller provides declarative updates for Pods and ReplicaSets (Deployment creates ReplicaSet to manage number of PODS).

You describe a desired state in a Deployment, and the Deployment Controller changes the actual state to the desired state at a controlled rate.

Update Image Tag

example tags:

  • nginx:1.0
  • nginx:2.0
  • nginx:3.0

With deployments you can upgrade from old image tag e.g: nginx:1.0 to nginx:3.0.

If something goes wrong then the image will roll back to old version nginx:1.0.

Hands On

vim nginx-deployment.yaml 

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80

Run the deployment 

kubectl apply -y nginx-deployment.yaml

kubectl get deployments

# example output:
# NAME               READY   UP-TO-DATE   AVAILABLE   AGE
# nginx-deployment   0/3     0            0           1s


kubectl get deploy

kubectl get rs

kubectl get pod

kubectl describe pod <pod-name>

Updating a deployment

kubectl set image deployment.v1.apps/nginx-deployment nginx=nginx:1.16.1

check if new version was changed: 

kubectl describe pod <pod-name>

search for image:

confirm that the version is set to 1.16.1

Rollback to a Previous Revision

check if there is old revision

kubectl get rs

output: 

NAME                       DESIRED
nginx-deployment-11111111  0 <-- previous revision
nginx-deployment-11111111  3


kubectl rollout undo deployment/nginx-deployment

kubectl get rs

output: 

NAME                       DESIRED
nginx-deployment-11111111  0 
nginx-deployment-11111111  3 <-- previous revision


kubectl get pod
kubectl describe pod <pod-name> | grep Image

check revision rollout history 

kubectl rollout history deployment/nginx-deployment

rollout to revision number 

kubectl rollout undo deployment/nginx-deployment --to-revision=2

Delete Deployment

kubectl get deploy

kubectl delete deploy <name>

Remember

imperetive is for learning, testing purpose.

But in production do it through definition files.

Link to Kubernetes deployment - official docs