Kubernetes is one of the most widely used container orchestration tool at present.
In the earlier post, I have explained how to deploy your spring boot application on Kubernetes cluster.
In this post, we will see how we can instruct Kubernetes to start a rolling update so that we can release a new version of our application without any downtime.
$ kubectl set image deployments/hostping hostping=pulgupta/hostping:latest
Lets breakdown this command. For more details on each construct of this command please see this post
- deployment/hostping: This is the name of our deployment
- pulgupta/hostping:latest: This is the new image which we want to use for our application
There is a lot of stuff going on behind the scene when we execute this command. Let us see what will Kubernetes do when this command is issued.
- It will fetch the latest tag of the image pulgupta/hostping
- It will start a new pod for the new image
- Once a new pod is available it will stop an old pod so that the total number of pods are equal to the number specified in the replica set
- Kubernetes will repeat this process until we have replaced all the old pods with the new pods.
- This all is done in a step by step process and hence we will have zero downtime for our application during this complete upgrade.
Pulkit Gupta 