K8s-Rollout-Rollback.md

LAB: K8s Rollout - Rollback

This scenario shows:

• how to roll out deployments with 2 different strategy: recreate and rollingUpdate,
• how to save/record deployments' revision while rolling out with "--record" (e.g. changing image):
  • imperative: "kubectl set image deployment rcdeployment nginx=httpd --record",
  • declerative, edit file: "kubectl edit deployment rolldeployment --record",
• how to rollback (rollout undo) the desired deployment revisions:
  • "kubectl rollout undo deployment rolldeployment --to-revision=2",
• how to pause/resume rollout:
  • pause: "kubectl rollout pause deployment rolldeployment",
  • resume: "kubectl rollout resume deployment rolldeployment",
• how to see the status of rollout deployment:
  • "kubectl rollout status deployment rolldeployment -w".

Steps

• Run minikube (in this scenario, K8s runs on WSL2- Ubuntu 20.04) ("minikube start")

• Create Yaml file (recreate-deployment.yaml) in your directory and copy the below definition into the file:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: rcdeployment
  labels:
    team: development
spec:
  replicas: 5                        # create 5 replicas
  selector:
    matchLabels:                     # labelselector of deployment: selects pods which have "app:recreate" labels
      app: recreate
  strategy:                          # deployment roll up strategy: recreate => Delete all pods firstly and create Pods from scratch.
    type: Recreate
  template:
    metadata:
      labels:                        # labels the pod with "app:recreate" 
        app: recreate
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

• Create Yaml file (rolling-deployment.yaml) in your directory and copy the below definition into the file:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: rolldeployment
  labels:
    team: development
spec:
  replicas: 10                     
  selector:
    matchLabels:                     # labelselector of deployment: selects pods which have "app:rolling" labels
      app: rolling
  strategy:
    type: RollingUpdate              # deployment roll up strategy: rollingUpdate => Pods are updated step by step, all pods are not deleted at the same time.
    rollingUpdate:                   
      maxUnavailable: 2              # shows the max number of deleted containers => total:10 container; if maxUnava:2, min:8 containers run in that time period
      maxSurge: 2                    # shows that the max number of containers    => total:10 container; if maxSurge:2, max:12 containers run in a time
  template:
    metadata:
      labels:                        # labels the pod with "app:rolling"
        app: rolling
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

• Run deployment:

• Watching pods' status (on linux: "watch kubectl get pods", on win: "kubectl get pods -w")

• Watching replica set's status (on linux: "watch kubectl get rs", on win: "kubectl get rs -w")

• Update image version ("kubectl set image deployment rcdeployment nginx=httpd"), after new replicaset and pods are created, old ones are deleted.

• With "recreate" strategy, pods are terminated:

• New pods are creating:

• New replicaset created:

• Delete this deployment:

• Run deployment (rolling-deployment.yaml):

• Watching pods' status (on linux: "watch kubectl get pods", on win: "kubectl get pods -w")

• Watching replica set's status (on linux: "watch kubectl get rs", on win: "kubectl get rs -w")

• Run: "kubectl edit deployment rolldeployment --record", it opens vim editor on linux to edit
• Find image definition, press "i" for insert mode, change to "httpd" instead of "nginx", press "ESC", press ":wq" to save and exit

• New pods are creating with new version:

• New replicaset created:

• Run new deployment version:

• New pods are creating with new version:

• New replicaset created:

• To show history of the deployments (important: --record should be used to add old deployment versions in the history list):

• To show/describe the selected revision:

• Rollback to the revision=1 (with undo: "kubectl rollout undo deployment rolldeployment --to-revision=1"):

• Pod status:

• Replicaset revision=1:

• It is possible to return from revision=1 to revision=2 (with undo: "kubectl rollout undo deployment rolldeployment --to-revision=2"):

• It is also to pause rollout:

• While rollback to the revision=3 from revision=2, it was paused:

• Resume the pause of rollout of deployment:

• Now deployment's revision is 3:

• It is also possible to see the logs of rollout with:

  • "kubectl rollout status deployment rolldeployment -w"

• Delete deployment: