Kubernetes Fluent Client for Node

The Kubernetes Fluent Client for Node is a fluent API for the Kubernetes JavaScript Client with some additional logic for Server Side Apply, Watch with retry/signal control, and Field Selectors. In addition to providing a human-friendly API, it also provides a simple way to create and manage resources in the cluster and integrate with K8s in a type-safe way.

To install the Kubernetes Fluent Client, run the following command:

npm install kubernetes-fluent-client

See below for some example uses of the library.

import { K8s, kind } from "kubernetes-fluent-client";

// Let's create a random namespace to work in
const namespace = "my-namespace" + Math.floor(Math.random() * 1000);

// This will be called after the resources are created in the cluster
async function demo() {
  // Now, we can use the fluent API to query for the resources we just created

  // You can use watch to monitor resources in the cluster and react to changes
  const watcher = K8s(kind.Pod).Watch((pod, phase) => {
    console.log(`Pod ${pod.metadata?.name} is ${phase}`);
  });

  // This will run until the process is terminated or the watch is aborted
  await watcher.start();

  // Let's abort the watch after 5 seconds
  setTimeout(watcher.close, 5 * 1000);

  // Passing the name to Get() will return a single resource
  const ns = await K8s(kind.Namespace).Get(namespace);
  console.log(ns);

  // This time we'll use the InNamespace() method to filter the results by namespace and name
  const cm = await K8s(kind.ConfigMap).InNamespace(namespace).Get("my-configmap");
  console.log(cm);

  // If we don't pass a name to Get(), we'll get a list of resources as KubernetesListObject
  // The matching resources will be in the items property
  const pods = await K8s(kind.Pod).InNamespace(namespace).Get();
  console.log(pods);

  // Now let's delete the resources we created, you can pass the name to Delete() or the resource itself
  await K8s(kind.Namespace).Delete(namespace);

  // Let's use the field selector to find all the running pods in the cluster
  const runningPods = await K8s(kind.Pod).WithField("status.phase", "Running").Get();
  runningPods.items.forEach(pod => {
    console.log(`${pod.metadata?.namespace}/${pod.metadata?.name} is running`);
  });

  // Get logs from a Deployment named "nginx" in the namespace
  const logs = await K8s(kind.Deployment).InNamespace(namespace).Logs("nginx");
  console.log(logs);
}

// Create a few resources to work with: Namespace, ConfigMap, and Pod
Promise.all([
  // Create the namespace
  K8s(kind.Namespace).Apply({
    metadata: {
      name: namespace,
    },
  }),

  // Create the ConfigMap in the namespace
  K8s(kind.ConfigMap).Apply({
    metadata: {
      name: "my-configmap",
      namespace,
    },
    data: {
      "my-key": "my-value",
    },
  }),

  // Create the Pod in the namespace
  K8s(kind.Pod).Apply({
    metadata: {
      name: "my-pod",
      namespace,
    },
    spec: {
      containers: [
        {
          name: "my-container",
          image: "nginx",
        },
      ],
    },
  }),
])
  .then(demo)
  .catch(err => {
    console.error(err);
  });

Generating TypeScript Definitions from CRDs

The Kubernetes Fluent Client can generate TypeScript definitions from Custom Resource Definitions (CRDs) using the generate command. This command will generate TypeScript interfaces for the CRDs in the cluster and save them to a file.

To generate TypeScript definitions from CRDs, run the following command:

kubernetes-fluent-client crd /path/to/input.yaml /path/to/output/folder

If you have a CRD in a file named crd.yaml and you want to generate TypeScript definitions in a folder named types, you can run the following command:

kubernetes-fluent-client crd crd.yaml types

This will generate TypeScript interfaces for the CRD in the crd.yaml file and save them to the types folder.

By default, the generated TypeScript interfaces will be post-processed to make them more user-friendly. If you want to disable this post-processing, you can use the --noPost flag:

kubernetes-fluent-client crd crd.yaml types --noPost

Community

To chat with other users & see some examples of the fluent client in active use, go to Kubernetes Slack and join #pepr channel.