rekustomize (Technical Preview / Aplha)

rekustomize lets you generate kustomize manifests. With rekustomize you can:

• Export resource manifests from live cluster using supported formats:
  • kustomize components (example)
  • helm charts (example)
• Filter exported resources or attributes based on customizable rules (example)
• Deduplicate manifests to ensure DRY principle
• Re-format existing manifests to follow customizable styles and to optimize duplicated manifests
• Convert existing manifests between formats, e.g. from helm chart to kustomize components

Deduplication of resources and attributes

rekustomize truly shines when it's used to generate manifests for multiple clusters at once. It will group correlad resources together and will also efficiently handle multiple versions of the same resource.

Helm template

This template shows how rekustomize can handle multiple versions of the same resource:

spec:
  {{- if index .Values.global "simple-app/Deployment/simple-app.spec.replicas" }}
  replicas: {{ index .Values.global "simple-app/Deployment/simple-app.spec.replicas" }}
  {{- end }} # simple-app/Deployment/simple-app.spec.replicas
  template:
    spec:
      containers:
      - image: {{ index .Values.global "simple-app/Deployment/simple-app.spec.template.spec.containers.[name=simple-app].image" }}
        name: simple-app

values.yaml defines presets to group values from different resources:

preset_values:
  prod:
    simple-app/ConfigMap/simple-app-env.data.ENV_VAR2: prod-value
    simple-app/Deployment/simple-app.spec.replicas: 5
  prod_test:
    simple-app/Deployment/simple-app.spec.template.spec.containers.[name=simple-app].image: example.com/simple-app:v1.2.345
  test:
    simple-app/ConfigMap/simple-app-env.data.ENV_VAR2: test-value
    simple-app/Deployment/simple-app.spec.replicas: 3

The generated presets are then assigned to each corresponding cluster:

• test-cluster-a:

  valuesInline:
    presets:
    - prod_test
    - test

• prod-cluster-b:

  valuesInline:
    presets:
    - prod
    - prod_test

Values, that are unique to a cluster are also supported:

• prod-cluster-a:

  valuesInline:
    global:
      simple-app/ConfigMap/simple-app-env.data.ENV_VAR3: prod-cluster-a-value

Kustomize components

If you use kustomize components format, similar overrides will be generated as strategic-merge patches:

• components/prod:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: simple-app
  namespace: simple-app
spec:
  replicas: 5

• components/test:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: simple-app
  namespace: simple-app
spec:
  replicas: 3

• components/prod_test

apiVersion: apps/v1
kind: Deployment
metadata:
  name: simple-app
  namespace: simple-app
spec:
  template:
    spec:
      containers:
      - name: simple-app
        image: example.com/simple-app:v1.2.345

rekustomization.yaml

To start using rekustomize, create a new folder with a rekustomization.yaml file where you can configure rekustomize behavior. Here's a breakdown of the helm chart example:

Cluster selector

By default rekustomize will use clusters defined in your KUBECONFIG file. You can select clusters using shell-like patterns:

clusters:
- names: dev-* # shell-like pattern
  tags: dev
- names: test-cluster-a,test-cluster-* # comma-separated list
  tags: test
- names: # yaml list
  - prod-cluster-a
  - prod-cluster-*
  tags: prod

In the future versions rekustomize will be able to use cluster metadata/labels from external sources, such as ClusterAPI, k0rdent, ArgoCD or Flux.

Resource selector

By default, rekustomize will generate manifests for all resources from all namespaces, excluding a pre-defined list of dynamic resources, like pods or events. You can customize that behavior in the export section:

export:
- namespaces: simple-app
  labelSelectors: ['!generated-by']
  apiResources:
    exclude: jobs.batch
- apiResources: namespaces
  names: simple-app

Resource attribute cleanup

If your live cluster resources contain attributes that you don't want to be included in the generated manifests, you can use SkipFilter to remove such unwanted attributes or values. The following example will remove any 'example.com/generated' annotations and 'dev.example.com/info' annotations with the value of 'flaky-tests':

filters:
- kind: SkipFilter
  fields:
  - metadata.annotations.example\.com/generated
  - metadata.annotations.dev\.example\.com/info[=flaky-tests]

Resource filters

You can also use SkipFilter to exclude entire resources from the generated manifests - to further refine resource selection:

filters:
- kind: SkipFilter
  resources:
  - kind: CronJob
    name: infra-canary

Chart metadata

This section defines metadata for the generated chart:

helmChart:
  name: simple-app
  version: v1.0

If no helmChart is specified, rekustomize will generate manifests in kustomize components format