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A Real Example


This demo implements the example application described in the Halkyon introduction. We encourage you to read it to familiarize yourself with Halkyon and its concepts.

In this demo, we will, moreover, go one step further in the simplification by generating our Halkyon resources based on information found in our applications' descriptors. This automatic generation is handled by dekorate.

Demo time

Build the full demo project using maven:

mvn clean package -f demo

As our Spring Boot maven projects use the dekorate halkyon starter


dekorate will generate a halkyon.yml|json file under the target/classes/META-INF/dekorate during the package phase. They will be next used to deploy the different components on the cluster with the help of the kubectl client tool.


A few explanation is needed here in order to understand what we did within the different projects to configure them and to simplify the process to deploy such a complex application on a cluster :-).

As Dekorate project supports 2 configuration's mode: Java Annotation or Annotationless using property file. When you prefer to use the Java annotations, then follow the instructions defined here after.

The @HalkyonComponent annotation has been added within the Spring Boot Application java class part of each Apache maven project.


    name = "fruit-client-sb",
    exposeService = true

When dekorate dependency will be called, it will scan the java classes, search about such annotations and if they exist, it will generate from the information provided a halkyon.yml file.

Additional information could also be calculated automatically as Dekorate supports different frameworks. When we use Spring Boot Dekorate, then the following parameters runtime and version will be set respectively to spring-boot and 2.1.6.RELEASE.

The @HalkyonLink annotation express, using an @Env, the name of the variable to be injected within the pod in order to let the Spring Boot Application to configure its HTTP Client to access the HTTP endpoint exposed by the backend service.


    name = "link-to-fruit-backend",
    componentName = "fruit-client-sb",
    type = Type.Env,
    envs = @Env(
        name = "ENDPOINT_BACKEND",
        value = "http://fruit-backend-sb:8080/api/fruits"

Like for the Client's component, we will define a @HalkyonComponent and @HalkyonLink annotations for the Backend component. The link will inject from the secret referenced, the parameters that the application will use to create a DataSource's java bean able to call the PostgreSQL instance.


    name = "fruit-backend-sb",
    exposeService = true
    name = "link-to-database",
    componentName = "fruit-backend-sb",
    type = Type.Secret,
    ref = "postgresql-db")

To configure the postgresql database to be used by the backend, we will use the @HalkyonCapability annotation to configure the database, the user, password and database name.

    name = "postgres-db",
    category = "database",
    kind = "postgres",
    version = "10",
    parameters = {
       @Parameter(name = "DB_USER", value = "admin"),
       @Parameter(name = "DB_PASSWORD", value = "admin"),
       @Parameter(name = "DB_NAME", value = "sample-db"),

If now, as defined within this demo project, you prefer to use the Annotationless mode supported by dekorate, then simply enrich the application.yml file of Spring Boot with the corresponding halkyon parameters.

By example the Backend component will be defined as such

    name: fruit-backend-sb
    deploymentMode: dev
    exposeService: true
    name: link-to-database
    componentName: fruit-backend-sb
    type: Secret
    ref: postgres-db-config
    name: postgres-db
    category: database
    type: postgres
    version: "10"
    - name: DB_USER
      value: admin
    - name: DB_PASSWORD
      value: admin
    - name: DB_NAME
      value: sample-db

To deploy the generated resource files on an existing cluster, execute the following commands:

kubectl create ns demo
kubectl apply -f fruit-client-sb/target/classes/META-INF/dekorate/halkyon.yml
kubectl apply -f fruit-backend-sb/target/classes/META-INF/dekorate/halkyon.yml

Wait a few moment and verify if the status of the components deployed are ready

oc get cp -n demo
NAME               RUNTIME       VERSION         AGE       MODE      STATUS    MESSAGE   REVISION
fruit-backend-sb   spring-boot   2.1.6.RELEASE   6m        dev       Ready     Ready     
fruit-client-sb    spring-boot   2.1.6.RELEASE   5m        dev       Ready     Ready     

oc get links -n demo
NAME                    AGE       STATUS    MESSAGE
link-to-database        6m        Ready     Ready
link-to-fruit-backend   5m        Ready     Ready

oc get capabilities -n demo
postgres-db   database             6m        Ready     Ready     

Then push the uber jar file within the pod using the following bash script

./demo/scripts/ fruit-backend sb demo
./demo/scripts/ fruit-client sb demo

Check now if the Component Client is replying and calls its HTTP Endpoint exposed in order to fetch the fruits data from the database consumed by the other microservice. The syntax to be used is not the same if the project is running on kubernetes vs openshift as k8s is creating an ingress resource while openshift a route

# Openshift Route
# export FRONTEND_ROUTE_URL=<service_name>.<hostname_or_ip>.<domain_name>
# oc get route/fruit-client-sb -n demo
curl http://${FRONTEND_ROUTE_URL}/api/client

# Kubernetes Ingress
curl -H "Host: fruit-client-sb" http://${FRONTEND_ROUTE_URL}/api/client

Switch from Dev to Build mode

Patch the Component which has been deployed and change the deploymentMode from dev to build. Next, wait till the Halkyon operator will create a Tekton Build's pod responsible to git clone the project and to perform a s2i build. When the image is pushed to the internal docker registry, then the pod of the runtime is created and the service's label will change to use the new service

kubectl patch cp fruit-backend-sb -p '{"spec":{"deploymentMode":"build"}}' --type=merge
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