LAB K102: Kubernetes Quick Dive
In this lab you are going to deploy the instavote application stack as described here in a kubernetes environment using kubectl commands. Later, you would learn how to do the same by writing declarive yaml syntax.
Purpose of this lab is to quickly get your app up and running and demonstrate kubernetes key features such as scheduling, high availability, scalability, load balancing, service discovery etc.
Deploying app with kubernetes
Launch vote application with kubernetes. (simiar to docker run command)
kubectl run vote --image=schoolofdevops/vote:v1
Since the above command is now deprecated, you could also use a alternate command such as
Following is an alternate. run it only if you have not used kubectl run above
kubectl create deployment vote --image=schoolofdevops/vote:v1
You could now validate that the instance of vote app is running by using the following commands,
kubectl get pods kubectl get deployments
Scale the vote app to run 4 instances.
kubectl scale deployment vote --replicas=4 kubectl get deployments,pods
kubectl get pods
The above command will list pods. Try to delete a few pods and observe how it affects the availability of your application.
kubectl delete pods vote-xxxx vote-yyyy kubectl get deploy,rs,pods
Publish the application (similar to using -P for port mapping)
kubectl expose deployment vote --type=NodePort --port 80 kubectl get svc
Connect to the app, refresh the page to see it load balancing. Also try to vote and observe what happens.
Deploying a new version
kubectl scale deployment vote --replicas=12 kubectl set image deployment vote vote=schoolofdevops/vote:v2
watch the rolling update in action
watch kubectl get deploy,rs,pods
Pre Test: Try to submit a vote from the frontend vote app. Does that work ?
Now lets launch rest of the apps.
kubectl create deployment redis --image=redis:alpine kubectl expose deployment redis --port 6379
optionally, you could launch rest of the services.
kubectl create deployment worker --image=schoolofdevops/worker kubectl create deployment db --image=postgres:9.4 kubectl expose deployment db --port 5432 kubectl create deployment result --image=schoolofdevops/vote-result kubectl expose deployment result --type=NodePort --port 80
- Try to submit a vote from the frontend vote app. Does that work ? If yes, try to deduce how it could connect to the backend applications such as redis.
- Access results ui application. When you submit vote, do the results change ?
Once you are done observing, you could delete it with the following commands,
kubectl delete deploy db redis vote worker result kubectl delete svc db redis result vote
When you deploy an application in kubernetes, you submit it to the api server/ cluster manager. Kubernetes automatically schedules it on a cluster, networks the pods, provides service discovery. In addition as you observed, your application is scalable, high available and is already running behind a load balancer.