Template GoTemplate
This is an example of implementing a template function using a go template.
This example uses a more sophisticated approach for building abstractions.
Function implementation
The function is implemented as an image, and built using make image.
The template is implemented as a go program with a go template. It parses the
functionConfig into a go struct and uses the kyaml module for parsing the
function input, and writing the function output.
- read the inputs (stdin)
- apply filters
- (custom filter) generate the nginx Deployment and Service from go templates using the functionConfig as the template input.
- merge the generated Deployment and Service with the input Deployment and Service if present
- set filenames on the Resources (
NAME.yaml) - format the Resources
- write the outputs (stdout)
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.yamlmay be changed and rerunningrunwill update only the parts changed in the template output.
Running the Example
Run the config with:
kustomize build --enable-alpha-plugins local-resource/
This will create the directory
local-resource/config
Add an annotation to the Deployment Resource and change the replica count of the
kind: Nginx Resource in example-use.yaml. Rerun the template:
kustomize build --enable-alpha-plugins local-resource/
The replica count should be updated, but your annotation should remain.