02-RollingUpdates-and-Rollback.md

Rolling Updates and Rollback

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In this section, we will take a look at rolling updates and rollback in a deployment

Rollout and Versioning in a Deployment

• When you first create a deployment it first create a rollout. A new rollout creates a new deployment revision (eg. v1)

• In the future, when the application is upgraded meaning when the container version is upgraded to a new one a new rollout is trigged and a new deploymnent revision is created named v2.

• This helps us keep track of the changes made to our deployment and enables us to rollback to a previous version of deployment if necessary.

  

Rollout commands

• You can see the status of the rollout by the below command

  $ kubectl rollout status deployment/myapp-deployment
  

• To see the history and revisions

  $ kubectl rollout history deployment/myapp-deployment
  

  

Deployment Strategies

• There are 2 types of deployment strategies

  1. Recreate
  2. RollingUpdate (Default Strategy)

  

kubectl apply

• To update a deployment, edit the deployment and make necessary changes and save it. Then run the below command.

  apiVersion: apps/v1
  kind: Deployment
  metadata:
   name: myapp-deployment
   labels:
    app: nginx
  spec:
   template:
     metadata:
       name: myap-pod
       labels:
         app: myapp
         type: front-end
     spec:
      containers:
      - name: nginx-container
        image: nginx:1.7.1
   replicas: 3
   selector:
    matchLabels:
      type: front-end       
  

  $ kubectl apply -f deployment-defination.yaml
  

• Alternate way to update a deployment say for example for updating an image.

  $ kubectl set image deplyoment/myapp-deployment nginx=nginx:1.9.1
  

  

Recreate vs RollingUpdate

Upgrades

Rollback

• To undo a change

  $ kubectl rollout undo deployment/myapp-deployment
  

kubectl create

• To create a deplyoment

  $ kubectl create deployment nginx --image=nginx
  

Summarize kubectl commands

$ kubectl create -f deployment-defination.yaml
$ kubectl get deployments
$ kubectl apply -f deployment-defination.yaml
$ kubectl set image deployment/myapp-deployment nginx=nginx:1.9.1
$ kubectl rollout status deployment/myapp-deployment
$ kubectl rollout history deployment/myapp-deployment
$ kubectl rollout undo deployment/myapp-deployment

K8s Reference Docs

• https://kubernetes.io/docs/concepts/workloads/controllers/deployment
• https://kubernetes.io/docs/tasks/run-application/run-stateless-application-deployment