openkruise.io/docs/cli-tool/kustomize-schema-generator.md

title
Kustomize Schema Generator

kruise-api provides tools for openkruise to generate kustomize schema files that support openkruise CRD, and provides the current available OpenAPI schema.

Schema Generator

When using kustomize to manage applications, in order to use strategic merge patches (SMPs) to process environment variables or any array type fields in resource definitions when using openkruise resources, the OpenAPI schema of openkruise CRD needs to contain the specified patch strategy. Schema Generator supports the function of quickly generating kustomize schema files based on the resource definition of openkruise. The specific way of generating kustomize schema files can be viewed in README.md.

Schema Usage

How to specify the schema file

kruise-api provides available OpenAPI schema files, you can use the latest version or specify the version of the OpenAPI schema file, just add the configuration block in kustomization.yaml like:

Use the latest version

openapi:
  path: https://raw.githubusercontent.com/openkruise/kruise-api/master/schema/openkruise_all_k8s_kustomize_schema.json

Use the specified version

openapi:
  path: https://raw.githubusercontent.com/openkruise/kruise-api/raw/<tag>/schema/openkruise_all_k8s_kustomize_schema.json

Or you can download kruise-api to the local, and specify the local file path in the configuration block:

openapi:
  path: <kruise-api-local-path>/schema/openkruise_all_k8s_kustomize_schema.json

Example

Take sidecarset as an example to introduce how to use kustomize OpenAPI schema to support the merge strategy of openkruise CRD in kustomize.

A complete definition of sidecarset is as follows:

apiVersion: apps.kruise.io/v1alpha1
kind: SidecarSet
metadata:
  name: test-sidecarset
spec:
  selector:
    matchLabels:
      app: nginx
  updateStrategy:
    type: RollingUpdate
    maxUnavailable: 1
  containers:
    - name: sidecar1
      image: centos:6.7
      command: ["sleep", "999d"]
      volumeMounts:
        - name: log-volume1
          mountPath: /var/log
    - name: sidecar2
      image: centos:6.8
      command: ["sleep", "999d"] 
      volumeMounts:
        - name: log-volume2
          mountPath: /var/log
  volumes: 
    - name: log-volume1
      emptyDir: {}
    - name: log-volume2
      emptyDir: {}

This sidecarset currently has two containers, sidecar1 and sidecar2, which mount two volumes named log-volume1 and log-volume2 respectively. Now If you want to add a new container sidecar3, mount a new volume named log-volume3, delete the sidecar1 container with corresponding volume, and then make some simple modifications to other fields. Then you can write the kustomization.yaml file with the merge strategy as follows:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- sidecarset.yaml

openapi:
  path: https://raw.githubusercontent.com/openkruise/kruise-api/master/schema/openkruise_all_k8s_kustomize_schema.json

patchesStrategicMerge:
- |-
  apiVersion: apps.kruise.io/v1alpha1
  kind: SidecarSet
  metadata:
    name: test-sidecarset
  spec:
    containers:
      - name: sidecar1
        $patch: delete
      - name: sidecar2
        volumeMounts:
          - name: log-volume3
            mountPath: /var/log3
      - name: sidecar3
        image: centos:6.9
        command: ["sleep", "102d"]
        volumeMounts:
          - name: log-volume3
            mountPath: /var/log
    volumes:
      - name: log-volume1
        $patch: delete
      - name: log-volume3
        emptyDir: {}  

The main thing added here is the openapi field and the path to the custom OpenAPI schema file. At this time, kustomize will determine the merge strategy of different fields according to the x-kubernetes-patch-* key in the OpenAPI schema file when patching. After executing the command kustomize build ., you can get the following results:

apiVersion: apps.kruise.io/v1alpha1
kind: SidecarSet
metadata:
  name: test-sidecarset
spec:
  containers:
  - command:
    - sleep
    - 999d
    image: centos:6.8
    name: sidecar2
    volumeMounts:
    - mountPath: /var/log3
      name: log-volume3
    - mountPath: /var/log
      name: log-volume2
  - command:
    - sleep
    - 102d
    image: centos:6.9
    name: sidecar3
    volumeMounts:
    - mountPath: /var/log
      name: log-volume3
  selector:
    matchLabels:
      app: nginx
  updateStrategy:
    maxUnavailable: 1
    type: RollingUpdate
  volumes:
  - emptyDir: {}
    name: log-volume3
  - emptyDir: {}
    name: log-volume2

You can refer to here for other common usage examples of openkruise crd merge strategy.