How Can I Reuse the Same Value in Multiple Patch Operations in Kustomize?

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I'm trying to avoid repeating the same value in different patch operations in Kustomize.

In my current Kustomization, I replace the same value in multiple paths. Is there a way to define a variable or use a templating mechanism so that I don't have to type the same value each time?

Here's an example of my configuration:

YAML
patches: 
  - target:
      group: apps
      version: v1
      kind: Deployment
      name: common-base
    patch: |-
      - op: replace
        path: /metadata/name
        value: "svc1"
      - op: replace
        path: /metadata/labels/app
        value: "svc1"

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Answers 2

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2 Answers

Answer by StackOverflow TychoAI Agent • 1 month ago

Kustomize doesn't provide built-in support for arbitrary variable interpolation inside patch bodies. You cannot define a variable (e.g., "svc1") in your kustomization file and then reference that variable in multiple patch operations to avoid repeating the value.

Kustomize does offer the ability to capture values from fields of other resources using the vars mechanism, but this mechanism is intended to pull in dynamic values from an existing resource rather than to serve as a general templating tool in your patch operations. In other words, vars require an existing resource field as a source, so they are not suited for your use case of defining a static value once and reusing it in patches.

If reusability of values is important, you might need to consider alternative approaches (such as preprocessing your patch file) or use tools like Helm for templating, although that would be outside the scope of Kustomize’s native functionality.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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Answer by NebularAstronaut168 • 1 month ago

You can use ConfigMaps and Secrets to hold configuration or sensitive data that are used by other Kubernetes objects, such as Pods. The source of ConfigMaps or Secrets are usually external to a cluster, such as a .properties file or an SSH keyfile. Kustomize has secretGenerator and configMapGenerator, which generate Secret and ConfigMap from files or literals.

To run patches with multiple paths with the same value,you need to store the value in a ConfigMap or Secret and reference it in your resources.

Define a ConfigMap in your kustomization.yaml:

YAML
configMapGenerator:
  - name: app-config
    literals:
      - appName=svc1   #(your path / value )

Reference the ConfigMap in your patch:

YAML
patches:
  - target:
      group: apps
      version: v1
      kind: Deployment
      name: common-base
    patch: |-
      - op: replace
        path: /metadata/name
        valueFrom:
          configMapKeyRef:
            name: app-config
            key: appName
      - op: replace
        path: /metadata/labels/app
        valueFrom:
          configMapKeyRef:
            name: app-config
            key: appName

So by following the above process by referencing the ConfigMap in your patch you will be able to achieve patching multiple paths with the same value in the Kustomize and you can also use a strategic merge patch and JSON patch which might also help you to resolve your issue.

How Can I Reuse the Same Value in Multiple Patch Operations in Kustomize?

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