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OpenShift Example

This example builds a Java application using Swarm that generates a fixed number of random integers. This example shows that a simple WildFly Swarm application can be deployed and configured in many different ways without having to change the actual application code:

  • It can be run as a standalone Java application using System Properties to be configured
  • It can be run in a Docker container using environment variables to be configured
  • It can be run in OpenShift application using Config Map to be configured

In this readme, we will describe the application and explain all the steps to:

  • build and run it
  • create a Docker image and run it in a container
  • push the image on the OpenShift registry
  • create an OpenShift application to deploy it
  • add a Config Map to configure the application


We will use Minishift) to deploy a local OpenShift container.

$ minishift start
  • Configure your shell to use docker and oc commands provided by Minishift
$ eval $(minishift docker-env)
$ eval $(minishift oc-env)
  • To check that Minishift is properly installed and configured, let's create a new project named 'numbers-project' that we will use later to deploy the Java application
$ oc login
// By default, the user credentials are `developer` : `developer`
$ oc new-project numbers

Description of the application

The Java application use WildFly Swarm to provide a single Web Service that returns a list of random positive integers (in a text/plain response, one integer per line).

The application accepts 2 configuration properties:

  • num.size - the number of integers to generate for each call to the Web Service
  • num.max - the maximum value for the generated integers.

These 2 properties are configured using the Eclipse MicroProfile Config API in the NumbersGenerator endpoint:

@ConfigProperty(name = "num.size", defaultValue = "3")
int numSize;

@ConfigProperty(name = "num.max", defaultValue = "" + Integer.MAX_VALUE)
int numMax;

According to their default values, each call to the application will return 3 integers that range between 0 and the maximum Integer value supported by Java.

Since the properties are using the Eclipse MicroProfile Config API, we can provide other values specific to our deployment stategy. We change them using System properties or environment variables for development and testing.

We also want to be able to configure them using OpenShift/Kubernetes Config Map.

To do so, we add a new type of ConfigSource to the application by customizing the MicroprofileFraction used by Swarm in the Main class:

swarm.fraction(new MicroProfileConfigFraction()
        .configSource("numbers-dir-config-source", (cs) -> {

When the application is started, it scans the /etc/config/numbers-app/ directory (if it exists) and reads each file to generate a property (with the file name as the key and the file content as the value).

In our case, we can create a file named num.size with 5 as its content to configure the application to return 5 integers instead of 3.

Build the application

$ mvn clean package

Run the standalone Java application

Let's run the application as a standalone UberJar and use a System property to configure it to return integers between 0 and 10:

$ java -Dnum.max=10 -jar target/microprofile-config-openshift-example-1.0-SNAPSHOT-swarm.jar

Create a Docker image

Let's now create a Docker image from the application using the simple Dockerfile:

FROM jboss/base-jdk:8

ADD target/microprofile-config-openshift-example-1.0-SNAPSHOT-swarm.jar /opt/wildfly-swarm.jar

ENTRYPOINT ["java", "-jar", "/opt/wildfly-swarm.jar"]

The Docker image is build by running the command:

$ docker build -t numbers/numbers-app .

Run the Docker image

Once we have minishift up and running, we can run the application in Docker:

$ docker run -e "num.size=2" -p 8080:8080 numbers/numbers-app

Note that we pass the enviroment variable num.size=2 to Docker to configure the application to return 2 integers (instead of 3).

We can check that the application is available from Docker (on my computer, the DOCKER_HOST value corresponds to the address that I'm using for the rest of the documentation):


Push the Docker image to the OpenShift Image registry

Next step is to push this Docker image to the OpenShift Image registry to be able to use it with OpenShift.

$ docker login -u developer -p $(oc whoami -t) $(minishift openshift registry)
$ docker tag numbers/numbers-app $(minishift openshift registry)/numbers/numbers-app
$ docker push $(minishift openshift registry)/numbers/numbers-app

The namespace is very important as it must match the name of the OpenShift project (numbers in this case).

Deploy the application on OpenShift

Now that the Docker image is in the OpenShift Image registry, we can add it to our OpenShift project.

  • Go to the OpenShift Web Console numbers project overview
  • Clik on Add to Project and select Deploy Image
  • Select the Image Stream Tag from the Docker image we just pushed to the registry
    • Namespace: numbers
    • Image Stream: numbers-app
    • tag: latest
  • Click on Create to deploy the application
  • Go back to the numbers project overview to see the deployment configuration of the number-app.

Create a route to the application

In order to access the application from outside OpenShift, we must create a route for it.


We have not provided any different values for the application configuration, so it is returning 3 integers between 0 and Integer.MAX_VALUE.

Create a Config Map

We will now create a Config Map to configure our application.


Note that the application now returns 5 integers instead of 3.

Update the Config Map

We can now update the config map to change the maximum value of the generated integers.

We can follow the same steps than before to add the num.max configuration or edit directly the YAML file corresponding to the Config Map:

  • On the right end corner, in the Actions button, choose Edit YAML
  • Add a new property under data: num.max: '100'
    apiVersion: v1
    kind: ConfigMap
      name: numbers-config
      namespace: numbers
      num.size: '5'
      num.max: '100'

The application is now configured to return 5 integers between 0 and 100.