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Add example for transformer configurations: crd
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‎examples/README.md

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* [remote target](remoteBuild.md) - Building a kustomization from a github URL
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* [json patch](jsonpatch.md) - Apply a json patch in a kustomization
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* [transformer configs](transformerconfigs/README.md) - Customize transformer configurations
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‎examples/transformerconfigs/README.md

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# Transformer Configurations
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Kustomize computes the resources by applying a series of transformers:
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- namespace transformer
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- prefix transformer
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- label transformer
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- annotation transformer
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- name reference transformer
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- variable reference transformer
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Each transformer takes a list of resources and modifies certain fields. The modification is based on the transformer's rule.
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The fields to update is represented by fieldSpec. Take prefix transformer as an example. It will add the prefix to `.metadata.name`
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field in each resources (except CustomResourceDefinition). Here `.metadata.name` is included by the prefix transformer configurations.
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Kustomize has a default set of configurations. They can be saved to local directory through `kustomize config save -d`. kusotmize allows modifying those configuration files and using them in `kustomize build` through `-t`. This tutorial shows how to customize those configurations to
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- [support a crd type](crd/README.md)
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- exclude some label selectors from commonLabels
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- add extra fields for variable substitution
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- add extra fields for name reference

‎examples/transformerconfigs/crd/README.md

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## Transformer Configurations - CRD
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This tutorial shows how to add transformer configurations to support a CRD type.
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### Get Default Config
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Get the default transformer configurations by
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<!-- @saveConfig @test -->
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```
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kustomize config save -d ~/.kustomize/config
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```
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The default configurations are save in directory `~/.kustomize/config` as several files
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> ```
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> commonannotations.yaml commonlabels.yaml nameprefix.yaml namereference.yaml namespace.yaml varreference.yaml
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> ```
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### Add Config for a CRD
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All transformers will be involved for a CRD type. The default configurations already include some common fieldSpec for all types:
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- nameprefix is added to `.metadata.name`
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- namespace is added to `.metadata.namespace`
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- labels is added to `.metadata.labels`
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- annotations is added to `.metadata.annotations`
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Thus those fieldSpec don't need to be added to support a CRD type.
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Consider a CRD type `MyKind` with fields
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- `.spec.secretRef.name` reference a Secret
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- `.spec.beeRef.name` reference an instance of CRD `Bee`
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- `.spec.containers.commands` as the list of container commands
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- `.spec.selectors` as the label selectors
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Add following file to configure the transformers for the above fields
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<!-- @addConfig @test -->
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```
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cat > ~/.kustomize/config/mykind.yaml << EOF
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commonLabels:
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- path: spec/selectors
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create: true
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kind: MyKind
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nameReference:
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- kind: Bee
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fieldSpecs:
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- path: spec/beeRef/name
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kind: MyKind
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- kind: Secret
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fieldSpecs:
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- path: spec/secretRef/name
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kind: MyKind
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varReference:
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- path: spec/containers/commands
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kind: MyKind
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EOF
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```
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### Apply config
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Create a kustomization with a `MyKind` instance.
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<!-- @createKustomization @test -->
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```
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DEMO_HOME=$(mktemp -d)
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cat > $DEMO_HOME/kustomization.yaml << EOF
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resources:
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- resources.yaml
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namePrefix: test-
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EOF
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cat > $DEMO_HOME/resources.yaml << EOF
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apiVersion: v1
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kind: Secret
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metadata:
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name: crdsecret
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data:
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PATH: YmJiYmJiYmIK
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---
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apiVersion: v1beta1
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kind: Bee
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metadata:
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name: bee
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spec:
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action: fly
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---
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apiVersion: jingfang.example.com/v1beta1
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kind: MyKind
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metadata:
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name: mykind
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spec:
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secretRef:
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name: crdsecret
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beeRef:
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name: bee
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EOF
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```
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Run `kustomize build` with customized transformer configurations and verify that
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the namereference is correctly resolved.
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<!-- @build @test -->
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```
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test 2 == \
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$(kustomize build $DEMO_HOME -t ~/.kustomize/config | grep -A 1 ".*Ref" | grep "test-" | wc -l); \
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echo $?
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```
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To understand this better, compare the output using default transformer configurations.
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<!-- @compareOutput -->
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```
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diff \
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<(kustomize build $DEMO_HOME) \
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<(kustomize build $DEMO_HOME -t ~/.kustomize/config ) |\
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more
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```
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The difference output should look something like
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> ```
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> 14c14
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> < name: bee
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> ---
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> > name: test-bee
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> 16c16
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> < name: crdsecret
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> ---
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> > name: test-crdsecret
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> ```
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‎examples/transformerconfigs/crd/kustomization.yaml

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resources:
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- resources.yaml
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namePrefix: test-

‎examples/transformerconfigs/crd/resources.yaml

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apiVersion: v1
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kind: Secret
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metadata:
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name: crdsecret
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data:
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PATH: YmJiYmJiYmIK
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---
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apiVersion: v1beta1
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kind: Bee
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metadata:
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name: bee
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spec:
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action: fly
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---
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apiVersion: jingfang.example.com/v1beta1
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kind: MyKind
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metadata:
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name: mykind
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spec:
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secretRef:
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name: crdsecret
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beeRef:
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name: bee

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