Task 5 - Upgrade Deployment
Objective: Mastering Deployment Upgrades and Downgrades
Discover upgrade strategies and learn how to effectively upgrade or downgrade deployments
Upgrade the deployment
Upgrading a deployment in Kubernetes, particularly changing the version of the application your Pods are running, can be smoothly managed using Kubernetes’ built-in strategies to ensure minimal downtime and maintain stability. The most popular strategies for upgrading a deployment are:
- Rolling Update (Default Strategy)
How It Works: This strategy updates the Pods in a rolling fashion, gradually replacing old Pods with new ones. Kubernetes automatically manages this process, ensuring that a specified number of Pods are running at all times during the update. Advantages: Zero downtime, as the service remains available during the update. It allows for easy rollback in case the new version is faulty.
Blue/Green Deployment This strategy involves running two versions of the application simultaneously - the current (blue) and the new (green) versions. Once the new version is ready and tested, traffic is switched from the old version to the new version, either gradually or all at once.
Canary Deployment A small portion of the traffic is gradually shifted to the new version of the application. Based on feedback and metrics, the traffic is slowly increased to the new version until it handles all the traffic.
ReCreate Strategy The “Recreate” strategy is a deployment strategy in Kubernetes that is particularly useful for managing stateful applications during updates. Unlike the default “RollingUpdate” strategy, which updates Pods in a rolling fashion to ensure no downtime, the “Recreate” strategy works by terminating all the existing Pods before creating new ones with the updated configuration or image.
the use case for Recreate Strategy is for stateful application where it’s critical to avoid running multiple versions of the application simultaneously.
Performing a Rolling Update
Objectives Perform a rolling update using kubectl. Updating an application Users expect applications to be available all the time, and developers are expected to deploy new versions of them several times a day. In Kubernetes this is done with rolling updates. A rolling update allows a Deployment update to take place with zero downtime. It does this by incrementally replacing the current Pods with new ones. The new Pods are scheduled on Nodes with available resources, and Kubernetes waits for those new Pods to start before removing the old Pods.
In the previous module we scaled our application to run multiple instances. This is a requirement for performing updates without affecting application availability. By default, the maximum number of Pods that can be unavailable during the update and the maximum number of new Pods that can be created, is one. Both options can be configured to either numbers or percentages (of Pods). In Kubernetes, updates are versioned and any Deployment update can be reverted to a previous (stable) version.
Rolling updates overview
Similar to application Scaling, if a Deployment is exposed publicly, the Service will load-balance the traffic only to available Pods during the update. An available Pod is an instance that is available to the users of the application.
Rolling updates allow the following actions:
Promote an application from one environment to another (via container image updates) Rollback to previous versions Continuous Integration and Continuous Delivery of applications with zero downtime
If a Deployment is exposed publicly, the Service will load-balance the traffic only to available Pods during the update.
In the following interactive tutorial, we’ll update our application to a new version, and also perform a rollback.
Perform Rolling Update
Create deployment with image set to kubernetes-bootcamp:v1
kubectl create deployment kubernetes-bootcamp --image=gcr.io/google-samples/kubernetes-bootcamp:v1 --replicas=4 kubectl expose deployment kubernetes-bootcamp --target-port=8080 --port=80- Verify the deployment
kubectl get deploymentExpected outcome
NAME READY UP-TO-DATE AVAILABLE AGE kubernetes-bootcamp 4/4 4 4 23s- check the service
use curlpod from cluster-internal to check the service
kubectl run curlpod --image=appropriate/curl --restart=Never --rm -it -- curl http://kubernetes-bootcamp.default.svc.cluster.localexpected outcome showing v=1
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-5485cc6795-4m7p9 | v=1 pod "curlpod" deletedupgrade deployment
Upgrade the deployment with image set to kubernetes-bootcamp:v2
kubectl set image deployments/kubernetes-bootcamp kubernetes-bootcamp=jocatalin/kubernetes-bootcamp:v2
kubectl rollout status deployment/kubernetes-bootcampexpected outcome
deployment.apps/kubernetes-bootcamp image updated
Waiting for deployment spec update to be observed...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 3 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 3 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 old replicas are pending termination...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 old replicas are pending termination...
deployment "kubernetes-bootcamp" successfully rolled outyou can find above that create new replicas first then delete old replicas to avoid service disruption.
- check the service
check the service use curlpod
kubectl run curlpod --image=appropriate/curl --restart=Never --rm -it -- curl http://kubernetes-bootcamp.default.svc.cluster.localexpected outcome showing v=2
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-7c6644499c-lsxm9 | v=2- rollback to old version
To rollback to orignal version, simple change the container image
kubectl set image deployments/kubernetes-bootcamp kubernetes-bootcamp=gcr.io/google-samples/kubernetes-bootcamp:v1
kubectl rollout status deployment/kubernetes-bootcampexpected outcome
kubectl rollout status deployment/kubernetes-bootcamp
deployment.apps/kubernetes-bootcamp image updated
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 0 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 0 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 3 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 3 out of 4 new replicas have been updated...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "kubernetes-bootcamp" rollout to finish: 1 old replicas are pending termination...
deployment "kubernetes-bootcamp" successfully rolled out- check the service use curlpod
kubectl run curlpod --image=appropriate/curl --restart=Never --rm -it -- curl http://kubernetes-bootcamp.default.svc.cluster.localexpected outcome showing v=1
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-5485cc6795-gvw6l | v=1
pod "curlpod" deletedRestart the deployment
- Restarting a deployment using kubectl rollout restart deployment
can be necessary or beneficial for Refreshing the Application, Troubleshooting etc in a Kubernetes environment. - check existing deployment
kubectl get pod -o wide -l app=kubernetes-bootcampexpected output
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES kubernetes-bootcamp-5485cc6795-brnv6 1/1 Running 0 4m54s 10.244.152.110 node-worker <none> <none> kubernetes-bootcamp-5485cc6795-hqkd9 1/1 Running 0 4m54s 10.244.152.109 node-worker <none> <none> kubernetes-bootcamp-5485cc6795-qb2jh 1/1 Running 0 4m55s 10.244.152.108 node-worker <none> <none> kubernetes-bootcamp-5485cc6795-zgcrd 1/1 Running 0 4m55s 10.244.152.107 node-worker <none> <none>- restart the deployment
Restart the deployment with default rolling update.
kubectl rollout restart deployment kubernetes-bootcamp- Verify the deployment
kubectl rollout status deployment kubernetes-bootcampexpected output
deployment "kubernetes-bootcamp" successfully rolled out- Verify the deployment after restart
kubectl get pod -o wide -l app=kubernetes-bootcampexpected output
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES kubernetes-bootcamp-d9f576d69-2q27m 1/1 Running 0 110s 10.244.152.113 node-worker <none> <none> kubernetes-bootcamp-d9f576d69-dwwc2 1/1 Running 0 110s 10.244.152.112 node-worker <none> <none> kubernetes-bootcamp-d9f576d69-hhqqm 1/1 Running 0 108s 10.244.152.114 node-worker <none> <none> kubernetes-bootcamp-d9f576d69-w5tpc 1/1 Running 0 108s 10.244.152.115 node-worker <none> <none>Notice that the Pod’s IP address has changed, and the deployment’s Pod template hash has also been updated to new prefix (d9f576d69). This indicates that all resources have been recreated following the kubectl rollout restart command.
clean up
kubectl delete svc kubernetes-bootcamp
kubectl delete deployment kubernetes-bootcampReview and Questions
- Use
kubectl runto create a POD with juice-shop image and add a label owner=dev - Use
kubectl create deploymentto create a deployment for juice-shop with replicas=2 and image=bkimminich/juice-shop:v15.0.0 - scale out juice-shop deployment from 2 replicas to 6 replicas
- use rolling upgrade to upgrade your juice-shop deployment to use version v16.0.0.
- Use
kubectlto find the specifcation for imagePullPolicy which is need for create a deployment. and set the juice-shop deployment container imagePullPolicy to use “IfNotPresent”.