render-gotpl

An KRM Function to render go templated manifests. An generator to be used with Kubectl, Kustomize or Kpt...

Usage: Shell implementation

An prototype.

kustomize build --enable-alpha-plugins --network --enable-exec --load-restrictor LoadRestrictionsNone ./example-exec

Usage: Go implementation

DRAFT, working but needs cleanup/lint

Features:

• go-getter interface to fetch dependencies
• render gotpl templates with sprig library and custom functions
• can render non-helm git repositories, subpaths etc..
• filter Kinds

Build:

docker build -t render-gotpl .

go build .

Kustomize usage:

kustomize build --enable-alpha-plugins --network ./example-container

In future kubectl versions:

kubectl -k apply ./example-exec

Function

KRM Fn specification

See upstream/other function examples:

• https://github.com/GoogleContainerTools/kpt-functions-catalog/blob/master/functions

My other functions:

• https://github.com/epcim/render-jsonnet-fn

Notable to mention:

• helm render function:
  • https://github.com/GoogleContainerTools/kpt-functions-catalog/tree/master/functions/go/render-helm-chart
  • https://github.com/GoogleContainerTools/kpt-functions-catalog/tree/master/examples/render-helm-chart-kustomize-private-git
  • https://github.com/GoogleContainerTools/kpt-functions-catalog/tree/master/examples/render-helm-chart-kustomize-inline-values

Values

values:
  nginx_cpu_request: "512m"
  nginx:
    cpu:
      limit:  "1000m"
    memory:
      limit:  "1024M"
  some:
  - list

GotplRender will either flatten all nested keys, so nginx_memory_limit: 1024 can be used in templates.

Sources

Public repos

sources:
- name: example
  repo: git::https://github.com/epcim/k8s-kustomize-apps//example/manifests?ref=main

See go-getter documentation for more details: https://github.com/hashicorp/go-getter#url-format

Private repos

WORKAROUND than solution, waiting for some best practice from upstream. Current interface to function does not allow to easily do such thing.

See this either: render-helm-chart-kustomize-private-git

Works:

# usage (private repos, mount pre-fetched repositories)
sources:
- name: minio
  repo: /r/repos/cicd-deployment//minio/k8s

# then:
kustomize build --enable-alpha-plugins --network --mount type=bind,src="$PWD/.repos",dst=/r/repos .

# dev
# see dockerfile for ENV variables
kustomize build --stack-trace --enable-alpha-plugins --network example --mount "type=bind,rw=true,src=$PWD/.output,dst=/r/output"

Not working: From private repository, with ssh key or token mounted.

apiVersion: fn.kpt.dev/v1
kind: RenderGotpl
metadata:
  name: render
  annotations:
    config.kubernetes.io/function: |
      container:
        network: true
        image: render-gotpl
        mounts:
        - type: bind
          src: /Users/xxx/.ssh/id_rsa
          dst: /tmp/id_rsa
sources:
- name: minio
  repo: git@gitlab.com:xxx/yyyy/cicd-deployment//minio/k8s?ref=master
  repoCreds: sshkey=/tmp/id_rsa