Hello World Helidon

This example is a Helidon-based service that returns a “Hello World” response when invoked. The application configuration uses the default, microprofile properties file.

Before you begin

Install Verrazzano by following the installation instructions.

NOTE: The Hello World Helidon example application deployment files are contained in the Verrazzano project located at <VERRAZZANO_HOME>/examples/hello-helidon, where <VERRAZZANO_HOME> is the root of the Verrazzano project.

Deploy the application

  1. To run the application in a namespace other than default namespace, create a namespace for the application and add a label identifying the namespace as managed by Verrazzano.

    $ kubectl create namespace hello-helidon
    $ kubectl label namespace hello-helidon verrazzano-managed=true istio-injection=enabled
  2. To deploy the application, apply the hello-helidon OAM resources.

    $ kubectl apply -f https://raw.githubusercontent.com/verrazzano/verrazzano/v1.4.8/examples/hello-helidon/hello-helidon-comp.yaml -n hello-helidon
    $ kubectl apply -f https://raw.githubusercontent.com/verrazzano/verrazzano/v1.4.8/examples/hello-helidon/hello-helidon-app.yaml -n hello-helidon
  3. Wait for the application to be ready.

    $ kubectl wait \
       --for=condition=Ready pods \
       --all \
       -n hello-helidon \

Explore the application

The Hello World Helidon microservices application implements a REST API endpoint, /greet, which returns a message {"message":"Hello World!"} when invoked.

NOTE: The following instructions assume that you are using a Kubernetes environment such as OKE. Other environments or deployments may require alternative mechanisms for retrieving addresses, ports, and such.

Follow these steps to test the endpoints.

  1. Get the generated host name for the application.

    $ HOST=$(kubectl get gateways.networking.istio.io hello-helidon-hello-helidon-gw \
         -n hello-helidon \
         -o jsonpath='{.spec.servers[0].hosts[0]}')
    $ echo $HOST
    # Sample output
  2. Get the EXTERNAL_IP address of the istio-ingressgateway service.

    $ ADDRESS=$(kubectl get service \
         -n istio-system istio-ingressgateway \
         -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
    $ echo $ADDRESS
    # Sample output
  3. Access the application.

    • Using the command line

      $ curl -sk \
         -X GET \
         https://${HOST}/greet \
         --resolve ${HOST}:443:${ADDRESS}
      # Expected response output
      {"message":"Hello World!"}

      If you are using nip.io, then you do not need to include --resolve.

    • Local testing with a browser

      Temporarily, modify the /etc/hosts file (on Mac or Linux) or c:\Windows\System32\Drivers\etc\hosts file (on Windows 10), to add an entry mapping the host name to the ingress gateway’s EXTERNAL-IP address. For example: hello-helidon.example.com

      Then you can access the application in a browser at https://<host>/greet.

      • If you are using nip.io, then you can access the application in a browser using the HOST variable (for example, https://${HOST}/greet).
      • If you are going through a proxy, then you may need to add *.nip.io to the NO_PROXY list.
    • Using your own DNS name

      Point your own DNS name to the ingress gateway’s EXTERNAL-IP address.

      • In this case, you would need to edit the hello-helidon-app.yaml file to use the appropriate value under the hosts section (such as yourhost.your.domain), before deploying the hello-helidon application.
      • Then, you can use a browser to access the application at https://<yourhost.your.domain>/greet.
  4. A variety of endpoints associated with the deployed application are available to further explore the logs, metrics, and such. You can access them according to the directions here.

Verify the deployed application

  1. Verify that the application configuration, domain, and ingress trait all exist.

    $ kubectl get ApplicationConfiguration -n hello-helidon
    $ kubectl get IngressTrait -n hello-helidon
  2. Verify that the hello-helidon service pods are successfully created and transition to the READY state. Note that this may take a few minutes and that you may see some of the services terminate and restart.

     $ kubectl get pods -n hello-helidon
     # Sample output
     NAME                                      READY   STATUS    RESTARTS   AGE
     hello-helidon-workload-676d97c7d4-wkrj2   2/2     Running   0          5m39s

Undeploy the application

  1. To undeploy the application, delete the Hello World Helidon OAM resources.

    $ kubectl delete -f https://raw.githubusercontent.com/verrazzano/verrazzano/v1.4.8/examples/hello-helidon/hello-helidon-app.yaml -n hello-helidon
    $ kubectl delete -f https://raw.githubusercontent.com/verrazzano/verrazzano/v1.4.8/examples/hello-helidon/hello-helidon-comp.yaml -n hello-helidon
  2. Delete the namespace hello-helidon after the application pod is terminated.

    $ kubectl delete namespace hello-helidon