How to deploy a feature with zero downtime in kubernetes

Question

Could you illustrate with an example How do i deploy a feature with zero downtime in kubernetes?

Answer 1

• By default Deployment in Kubernetes uses RollingUpdate as a strategy. 

• Let's say we have an example that creates a deployment in Kubernetes.

kubectl run nginx --image=nginx # creates a deployment
○ → kubectl get deploy
NAME    DESIRED  CURRENT UP-TO-DATE   AVAILABLE AGE
nginx   1  1 1            0 7s

• Now let’s assume we are going to update the nginx image

kubectl set image deployment nginx nginx=nginx:1.15 # updates the image

• Now when we check the replica sets

kubectl get replicasets # get replica sets

NAME               DESIRED CURRENT READY   AGE
nginx-65899c769f   0 0 0       7m
nginx-6c9655f5bb   1 1 1       13s

• From the above, we can notice that one more replica set was added and then the other replica set was brought down

kubectl rollout status deployment nginx 

# check the status of a deployment rollout

kubectl rollout history deployment nginx

# check the revisions in a deployment

○ → kubectl rollout history deployment nginx
deployment.extensions/nginx
REVISION  CHANGE-CAUSE
1         <none>
2         <none>