This example shows how to create a small OSGi based application and deploy it to kubernetes.
Install
- jdk 1.8
- maven >= 3.5
- docker
Checkout the source
git clone git@github.com:cschneider/osgi-example-kubernetes.git
Start eclipse and import from top level directory as existing maven projects.
mvn clean install
java -jar starter/target/app.jar
http://localhost:8080/hello
This should return Hello World and is served by a JAX-RS service.
http://localhost:8080/systemready
Returns the ready state of the system. At the start this might return YELLOW but after a very short while it should return GREEN.
http://localhost:8080/system/console
Allows access to the felix webconsole to look into all details of the system.
You need access to a kubernetes cluster. To achieve this either install minikube or get a kubernetes cluster from a cloud provider.
For my tests I installed the kubernetes service on Azure. This only needs a few clicks. The default settings work fine.
This does a maven build plus docker container creation and docker push.
export DOCKER_USERNAME=<your user>
export DOCKER_PASSWORD=<your password>
sh build.sh
Deploy to your kubernetes Cluster
sh deploy.sh
This installs the docker container as a deployment with one instance and a service with a load balancer for access.
kubectl get pods
It should display output like below. We should have one pod installed that contains our OSGi app.
NAME READY STATUS RESTARTS AGE
example-systemready-6b7985c88f-tcfmh 1/1 Running 0 10h
kubectl get services
Here we should see a service that makes our example available on an external ip with a load balancer.
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
example-systemready LoadBalancer 10.0.207.16 104.211.55.231 80:30215/TCP 22h
Now test the steps from "access the deployment" above with your external IP instead of localhost and with port 80.
You can use this command to get the external IP:
kubectl get svc example-systemready -o json | jq -r .status.loadBalancer.ingress[0].ip
Change some code.
Then do
sh build.sh
kubectl delete pod -l run=example-systemready
This builds and deploys the new docker image and then deletes all existing pods. This will cause kubernetes to spawn a new pod which loads the new image.
Our example is deployed in kubernetes with a liveness check. If this check fails then kubernetes will restart the pod.
To see current pods run this in a shell. It will wait and display changes.
kubectl get pods -o wide -w
Now let's report not alive:
curl -X POST http://ext-ip/control/notalive
After a few seconds we should see the number of restarts increase in the shell where we check for the pods. Alternatively you can use the kubernetes dashboard and look into the running pod. It will show failed readiness and liveness checks and report that the instance will be killed and restarted.
Our example is deployed in kubernetes with a liveness check. If this check fails then kubernetes will restart the pod.
To see current pods run this in a shell. It will wait and display changes.
kubectl get pods -o wide -w
Focus on the ready column. It should report "1/1".
Now let's report not ready for 60 seconds:
curl -X POST http://ext-ip/control/notready
Then quickly check the ready probe:
http://ext-ip/systemready
It will now report RED. Keep an eye on the pod list above. It should update with "0/1" in the ready column. Once kubernetes consideres the pod as not ready it will take it out of the load balancer. So when we check the ready state above again it will not respond.
After the 60 seconds it should go back to "1/1". The ready state in our probe will return to GREEN.
Scale the deployment to 2 intances and check how the cluster now behaves.
kubectl scale deployments/example-systemready --replicas=2