Template HereDoc

This is an example of implementing a template function using a heredoc.

This example uses the simplest approach for building abstractions.

Function implementation

The function is implemented as an image, and built using make image.

The template is implemented as a heredoc, which substitutes environment variables into a static string.

This simple implementation uses kustomize fn run wrap -- to perform the heavy lifting of implementing the function interface.

• parse functionConfig from stdin into environment variables
• merge script output with items from stdin

Function invocation

The function is invoked by authoring a local Resource with metadata.annotations.[config.kubernetes.io/function] and running:

kustomize fn run local-resource/

This generates the local-resource/config directory containing the template output.

• the template output may be modified by adding fields -- such as initContainers, sidecarConatiners, cpu resource limits, etc -- and these fields will be retained when re-running run
• the function input example-use.yaml may be changed and rerunning run will update only the parts changed in the template output.

Running the Example

Run the config with:

 kustomize fn run local-resource/

This will create the directory

local-resource/config

Add an annotation to the StatefulSet Resource and change the replica count of the kind: CockroachDB Resource in example-use.yaml. Rerun the template:

kustomize fn run local-resource/

The replica count should be updated, but your annotation should remain.