This example implements a simple Hello World REST service.
- Maven 3.5 or newer
- Java SE 8 or newer
- Docker 17 or newer to build and run docker images
- Kubernetes minikube v0.24 or newer to deploy to Kubernetes (or access to a K8s 1.7.4 or newer cluster)
- Kubectl 1.7.4 or newer to deploy to Kubernetes
Verify prerequisites
java --version
mvn --version
docker --version
minikube version
kubectl version --short
mvn package
java -jar target/quickstart-se.jar
# 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
docker build -t quickstart-se target
docker run --rm -p 8080:8080 quickstart-se:latest
Exercise the application as described above
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.
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.
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
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