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Helidon Example: quickstart-se

This example implements a simple Hello World REST service.

Prerequisites

  1. Maven 3.5 or newer
  2. Java SE 8 or newer
  3. Docker 17 or newer to build and run docker images
  4. Kubernetes minikube v0.24 or newer to deploy to Kubernetes (or access to a K8s 1.7.4 or newer cluster)
  5. Kubectl 1.7.4 or newer to deploy to Kubernetes

Verify prerequisites

java --version
mvn --version
docker --version
minikube version
kubectl version --short

Build

mvn package

Start the application

java -jar target/quickstart-se.jar

Exercise the application

# Get the default greeting
curl -X GET http://localhost:8080/greet
{"message":"Hello World!"}

# Get a greeting for Joe
curl -X GET http://localhost:8080/greet/Joe
{"message":"Hello Joe!"}

# Change the greeting using PUT
curl -X PUT http://localhost:8080/greet/greeting/Hola
{"gretting":"Hola"}

# Get a greeting for Jose, notice Hello is now Hola
curl -X GET http://localhost:8080/greet/Jose
{"message":"Hola Jose!"}

# Change greeting by POSTing JSON
curl -X POST -d '{"greeting" : "Howdy"}' http://localhost:8080/greet/greeting

# Change greeting by POSTing JSON to a slow handler
# Using asynchronous processing
curl -X POST -d '{"greeting" : "Hi"}' http://localhost:8080/greet/slowgreeting

Build the Docker Image

docker build -t quickstart-se target

Start the application with Docker

docker run --rm -p 8080:8080 quickstart-se:latest

Exercise the application as described above

Metrics

The application makes metrics available at the /metrics/ endpoint. You can get metrics in JSON and Prometheus format:

# Get Metrics in JSON format
curl -H 'Accept: application/json' -X GET http://localhost:8080/metrics/ | json_pp

# Get Metrics in Prometheus format
curl -H 'Accept: text/plain' -X GET http://localhost:8080/metrics/

To configure Prometheus to scrape metrics from the application add this to prometheus.yml under scrape_configs::

  - job_name: 'helidon'

    metrics_path: '/metrics/'
    # metrics_path defaults to '/metrics'
    # scheme defaults to 'http'.

    static_configs:
    - targets: ['localhost:8080']

Once Prometheus is runnining access the console (e.g. localhost:9090/graph) and click Graph. Enter application:accessctr then click Execute.

You should see the graph plotting the application's accessctr metric. Exercise the application some more using the curl commands that were described earlier. Click Execute again and you should see the counter increase.

Tracing

By default the application is configured to connect to zipkin at http://localhost:9411. This is configured in application.yaml.

Start the Zipkin docker container:

docker run -d -p 9411:9411 openzipkin/zipkin

Then exercise the application:

curl -X POST -d '{"greeting" : "Howdy"}' http://localhost:8080/greet/slowgreeting

To view traces go to http://localhost:9411/zipkin/

Click on "Find a Trace". Click on "Find Traces" and sort by newest. You should see a roughly 2 second trace.

Deploy the application to Kubernetes

kubectl cluster-info                # Verify which cluster
kubectl get pods                    # Verify connectivity to cluster
kubectl create -f target/app.yaml   # Deply application
kubectl get service quickstart-se  # Get service info