JHipster-generated Kubernetes configuration

Preparation

You will need to push your image to a registry. If you have not done so, use the following commands to tag and push the images:

$ docker image tag testdeploy deveshtamhane/testdeploy
$ docker push deveshtamhane/testdeploy

Deployment

You can deploy all your apps by running the below bash command:

./kubectl-apply.sh

Exploring your services

## Scaling your deployments

You can scale your apps using

$ kubectl scale deployment --replicas

## zero-downtime deployments

The default way to update a running app in kubernetes, is to deploy a new image tag to your docker registry and then deploy it using

$ kubectl set image deployment/-app =

Using livenessProbes and readinessProbe allow you to tell Kubernetes about the state of your applications, in order to ensure availablity of your services. You will need minimum 2 replicas for every application deployment if you want to have zero-downtime deployed. This is because the rolling upgrade strategy first kills a running replica in order to place a new. Running only one replica, will cause a short downtime during upgrades.

## JHipster registry

The registry is deployed using a headless service in kubernetes, so the primary service has no IP address, and cannot get a node port. You can create a secondary service for any type, using:

$ kubectl expose service jhipster-registry --type=NodePort --name=exposed-registry

and explore the details using

$ kubectl get svc exposed-registry

For scaling the JHipster registry, use

$ kubectl scale statefulset jhipster-registry --replicas 3

## Troubleshooting

> my apps doesn't get pulled, because of 'imagePullBackof'

Check the registry your Kubernetes cluster is accessing. If you are using a private registry, you should add it to your namespace by `kubectl create secret docker-registry` (check the [docs](https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/) for more info)

> my applications get killed, before they can boot up

This can occur if your cluster has low resource (e.g. Minikube). Increase the `initialDelySeconds` value of livenessProbe of your deployments

> my applications are starting very slow, despite I have a cluster with many resources

The default setting are optimized for middle-scale clusters. You are free to increase the JAVA_OPTS environment variable, and resource requests and limits to improve the performance. Be careful!


> my SQL-based microservice is stuck during Liquibase initialization when running multiple replicas

Sometimes the database changelog lock gets corrupted. You will need to connect to the database using `kubectl exec -it` and remove all lines of liquibases `databasechangeloglock` table.