Fabric8 Kubernetes Java Client

In my last article we learned how we can use the official Kubernetes Java Client to operate on a Kubernetes cluster.

In this article we are going to learn how we can use the most popular Kubernetes Client for Java.

Installation

For using fabric8’s Kubernetes client with Bazel, we need to have the maven repository configured in the workspace and the kubernetes-client artifact:

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load('@bazel_tools//tools/build_defs/repo:http.bzl', 'http_archive')

RULES_JVM_EXTERNAL_TAG = '4.1'
RULES_JVM_EXTERNAL_SHA = 'f36441aa876c4f6427bfb2d1f2d723b48e9d930b62662bf723ddfb8fc80f0140'

http_archive(
  name = 'rules_jvm_external',
  strip_prefix = 'rules_jvm_external-%s' % RULES_JVM_EXTERNAL_TAG,
  sha256 = RULES_JVM_EXTERNAL_SHA,
  url = 'https://github.com/bazelbuild/rules_jvm_external/archive/%s.zip' % RULES_JVM_EXTERNAL_TAG,
)

load('@rules_jvm_external//:defs.bzl', 'maven_install')

maven_install(
  artifacts = [
    'io.fabric8:kubernetes-client:6.1.1',
  ],
  repositories = [
    'https://repo1.maven.org/maven2',
  ],
)

We also need to add the kubernetes client packages as dependencies:

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java_binary(
  name = 'demo',
  srcs = glob(['*.java']),
  main_class = 'demo.PodLister',
  deps = [
    '@maven//:io_fabric8_kubernetes_client',
    '@maven//:io_fabric8_kubernetes_client_api'
  ],
)

Example usage

In my Kubernetes client post we learned how to list all pods, let’s see how we can do the same thing with fabric8:

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package demo;

import io.fabric8.kubernetes.client.KubernetesClient;
import io.fabric8.kubernetes.client.KubernetesClientBuilder;

public class PodLister {
  public static void main(String[] args) {
    try (KubernetesClient client = new KubernetesClientBuilder().build()) {
      client.pods().inNamespace("default").list().getItems().forEach(
        pod -> System.out.println(pod.getMetadata().getName())
      );
    } catch (Exception ex) {
      ex.printStackTrace();
    }
  }

If we compare it with the official Kubernetes Client, Frabric8’s API is much easier to follow. In the official client we had a method with a long list of arguments that are hard to read:

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api.listPodForAllNamespaces(null, null, null, null, null, null, null, null, null, null);

While here, it’s easier to understand what’s happening without having to look at the documentation:

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client.pods().inNamespace("default").list()

A full example can be found at Fabric8 Kubernetes Java Client demo

Conclusion

Fabric8’s Kubernetes Client provides an easier to read API compared to the official Kubernetes Java Client.

In this article I showed a very simple usage, but I’m planning on building a controller where we will use a lot more features.