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Kubernetes client

This page details Kubernetes client.

Dependency

<dependency>
  <groupId>io.yupiik.fusion</groupId>
  <artifactId>fusion-kubernetes-client</artifactId>
  <version>${fusion.version}</version>
</dependency>

Usage

The KubernetesClient implements java.net.http.HttpClient. It is typically used from an operator or a cloud native application to call the Kubernetes API using a plain and very light HTTP client from the JVM.

TIP

you can combine it with the enhanced HTTP client configuring it in the KubernetesClientConfiguration. It is recommended to do it using setClientWrapper on the configuration and pass the automatically created client to ExtendedHttpClientConfiguration.setDelegate to avoid having to handle the SSLContext yourself.

 
final var conf = new KubernetesClientConfiguration()
    .setClientWrapper(client -> new ExtendedHttpClient(new ExtendedHttpClientConfiguration()
        .setDelegate(client)));
final var k8s = new KubernetesClient(conf);

// now call any API you need:
final var response = k8s.send(
        HttpRequest.newBuilder()
                .GET()
                .uri(URI.create(
                    "https://kubernetes.api/api/v1/namespaces/" + k8s.namespace().orElse("default") + "/configmaps?" +
                            "includeUninitialized=false&" +
                            "limit=1000&" +
                            "timeoutSeconds=600")
                .header("Accept", "application/json")
                .build(),
        HttpResponse.BodyHandlers.ofString(StandardCharsets.UTF_8));
// handle the response
IMPORTANT

as you can see, there is no need to pass the token to the request, it is done under the hood by the KubernetesClient. The other important note is that https://kubernetes.api is automatically replaced by the conf.getMaster() value. This enables your code to stay more straightforward in general but if you pass them, the client will handle it properly too.

Configuration

KubernetesClientConfiguration reads the master URL from the KUBERNETES_SERVICE_HOST/KUBERNETES_SERVICE_PORT environment variables when running in cluster and supports:

  • token path or evaluator (/var/run/secrets/kubernetes.io/serviceaccount/token),

  • client/server certificates and private key,

  • skipTls,

  • a kubeconfig for out-of-cluster usage,

  • a client customizer/wrapper to decorate the underlying HttpClient.

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