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Jsonpatch (RFC 6902)

A jsonpatch is a json file or json file content that includes the desired changes to apply to a kubernetes resource

A jsonpatch can do almost everything a patchStrategicMerge can do, but with a briefer syntax

Using a file (path)

ingress_patch.json

[
  {"op": "replace",
   "path": "/spec/rules/0/host",
   "value": "foo.bar.io"},

  {"op": "replace",
   "path": "/spec/rules/0/http/paths/0/backend/servicePort",
   "value": 80},

  {"op": "add",
   "path": "/spec/rules/0/http/paths/1",
   "value": { "path": "/healthz", "backend": {"servicePort":7700} }}
]

kustomization.yaml

patches:
- path: ingress_patch.json
  target:
    group: networking.k8s.io
    version: v1beta1
    kind: Ingress
    name: my-ingress

Using inline patch

If we want to use the inline option in a json6902 patch, we must provide it this way.

"op" can be "add", "replace", or "remove".

patches:
  - patch: |-
      - op: replace
        path: /spec/template/spec/containers/0/image
        value: nginx:1.21.0

Special characters

The ~ character is used as an escape character

~0

In Kustomize, "~0" typically refers to a special path indicating the current directory where the kustomization.yaml file is located. This is a shorthand for referencing files within the same directory as the Kustomization configuration. It's commonly used for defining paths to base Kubernetes manifests or patches that Kustomize will use to customize and deploy resources

~0 represents a ~ character itself.

~1

In Kustomize, "~1" represents a backslash, which is used to escape characters in a string. When used in a path, it means to include a forward slash ("/"). So, "~1" translates to "/" in Kustomize paths.

patches:
  - patch: |-
      - op: add
        path: /metadata/labels/app.kubernetes.io~1version
        value: 1.21.0

https://github.com/kubernetes-sigs/kustomize/issues/1256 https://github.com/kubernetes-sigs/kustomize/issues/907

Notes

In the standard JSON merge patch, JSON objects are always merged but lists are always replaced

  • jsonpatch.com

https://jsonpatch.com/

  • JavaScript Object Notation (JSON) Patch RFC 6902

https://datatracker.ietf.org/doc/html/rfc6902

JSON6902