In the previous chapter, we explored some of the core concepts for application updates using the old rolling-update method. Starting with version 1.2, Kubernetes added the Deployment construct, which improves on the basic mechanisms of rolling-update and Replication Controllers. As the name suggests, it gives us a finer control of the code deployment itself. Deployments allow us to pause and resume application rollouts. Additionally, it keeps a history of past deployments and allows the user to easily rollback to previous versions.
In the following, listing 5-1, we can see that the definition is very similar to a Replication Controller. The main difference is that we now have an ability to make changes and updates to the deployment objects and let Kubernetes manage updating the underlying pods and replicas for us:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: node-js-deploy
labels:
name: node-js-deploy
spec:
replicas: 1
template:
metadata:
...