Scale with Custom Resource #

This document walks you through how to scale custom Kubernetes resources using kwokctl scale.

The kwokctl scale command supports scaling custom resource types beyond the built-in node and pod types. Any resource can be scaled by defining a KwokctlResource configuration that provides a name, default parameters, and a Go template for the resource manifest.

Create a Cluster #

kwokctl create cluster

Create Nodes #

kwokctl scale node --replicas 2

Define a Deployment Resource #

Create a KwokctlResource manifest that acts as the template for Deployments. Save the following content as deployment-resource.yaml:

apiVersion: config.kwok.x-k8s.io/v1alpha1
kind: KwokctlResource
metadata:
  name: deployment
parameters:
  replicas: 1
  containers:
  - name: container-0
    image: busybox
template: |-
  apiVersion: apps/v1
  kind: Deployment
  metadata:
    name: {{ Name }}
    namespace: {{ or Namespace "default" }}
  spec:
    replicas: {{ .replicas }}
    selector:
      matchLabels:
        app: {{ Name }}
    template:
      metadata:
        labels:
          app: {{ Name }}
      spec:
        containers:
        {{ range $index, $container := .containers }}
        - name: {{ $container.name }}
          image: {{ $container.image }}
        {{ end }}  

The template field uses Go template syntax. The built-in functions Name, Namespace, and Index are available, where Name is the generated resource name, Namespace is the value of the --namespace flag (falling back to "default"), and Index is the zero-based replica index.

Scale Deployments #

Use --config to load the resource definition and --replicas to set the number of Deployments to create:

kwokctl scale deployment --replicas 5 --config ./deployment-resource.yaml

Use --param to override default template parameters at runtime. For example, set each Deployment to have 3 replicas:

kwokctl scale deployment --replicas 5 --param '.replicas=3' --config ./deployment-resource.yaml

Persist the Resource Definition #

Instead of passing --config every time, you can append the KwokctlResource to the default configuration file (~/.kwok/kwok.yaml) so that kwokctl scale deployment works without any extra flags:

cat deployment-resource.yaml >> ~/.kwok/kwok.yaml
kwokctl scale deployment --replicas 5 --param '.replicas=3'

Scale Deployments into a Specific Namespace #

Create the target namespace first, then pass it with --namespace:

kubectl create namespace my-namespace
kwokctl scale deployment --replicas 5 --namespace my-namespace --param '.replicas=3' --config ./deployment-resource.yaml

Verify #

kubectl get deployments -A

kubectl get pods -A

The output should show deployment-000000 through deployment-000004 (five deployments), each with the pods spawned by the Kubernetes Deployment controller:

NAMESPACE   NAME                READY   UP-TO-DATE   AVAILABLE   AGE
default     deployment-000000   3/3     3            3           5s
default     deployment-000001   3/3     3            3           5s
default     deployment-000002   3/3     3            3           5s
default     deployment-000003   3/3     3            3           5s
default     deployment-000004   3/3     3            3           5s

Delete the Cluster #

kwokctl delete cluster