Quarkus - Kubernetes Client

Quarkus includes the kubernetes-client extension which enables the use of the Fabric8 Kubernetes Client in native mode while also making it easier to work with.

Having a Kubernetes Client extension in Quarkus is very useful in order to unlock the power of Kubernetes Operators. Kubernetes Operators are quickly emerging as a new class of Cloud Native applications. These applications essentially watch the Kubernetes API and react to changes on various resources and can be used to manage the lifecycle of all kinds of complex systems like databases, messaging systems and much much more. Being able to write such operators in Java with a the very low footprint that native images provide is a great match.

Configuration

Once you have your Quarkus project configured you can add the kubernetes-client extension to your project by running the following command in your project base directory.

mvn quarkus:add-extension -Dextensions="kubernetes-client"

This will add the following to your pom.xml:

    <dependency>
        <groupId>io.quarkus</groupId>
        <artifactId>quarkus-kubernetes-client</artifactId>
    </dependency>

Testing

To make testing against a mock Kubernetes API extremely simple, Quarkus provides the KubernetesMockServerTestResource which automatically launches a mock of the Kubernetes API server and sets the proper environment variables needed so that the Kubernetes Client configures itself to use said mock. Tests can inject the mock and set it up in any way necessary for the particular testing using the @MockServer annotation.

Here is an example of such test:

@QuarkusTestResource(KubernetesMockServerTestResource.class)
@QuarkusTest
public class KubernetesClientTest {

    @MockServer
    private KubernetesMockServer mockServer;

    @Test
    public void before() {
        final Pod pod1 = new PodBuilder().withNewMetadata().withName("pod1").withNamespace("test").and().build();
        final Pod pod2 = new PodBuilder().withNewMetadata().withName("pod2").withNamespace("test").and().build();

        mockServer.expect().get().withPath("/api/v1/namespaces/test/pods")
                .andReturn(200,
                        new PodListBuilder().withNewMetadata().withResourceVersion("1").endMetadata().withItems(pod1, pod2)
                                .build())
                .always();
    }

    @Test
    public void testInteractionWithAPIServer() {
        RestAssured.when().get("/pod/test").then()
                .body("size()", is(2));
    }

}

Note that to take advantage of these features, the quarkus-test-kubernetes-client dependency needs to be added, for example like so:

    <dependency>
        <groupId>io.quarkus</groupId>
        <artifactId>quarkus-test-kubernetes-client</artifactId>
        <scope>test</scope>
    </dependency>