Helmfile KCL Plugin
Introduction
Helmfile is a declarative spec for deploying helm charts. It lets you...
- Keep a directory of chart value files and maintain changes in version control.
- Apply CI/CD to configuration changes.
- Periodically sync to avoid skew in environments.
KCL can be used to create functions to mutate and/or validate the YAML Kubernetes Resource Model (KRM) input/output format, and we provide Kustomize KCL functions to simplify the function authoring process.
Prerequisites
- Install helmfile
- Prepare a Kubernetes cluster
Quick Start
Let’s write a KCL function which add annotation managed-by=helmfile-kcl
only to Deployment resources.
1. Get the Example
git clone https://github.com/kcl-lang/helmfile-kcl.git
cd ./helmfile-kcl/examples/hello-world/
We can execute the command to show config
cat helmfile.yaml
The output is
repositories:
- name: prometheus-community
url: https://prometheus-community.github.io/helm-charts
releases:
- name: prom-norbac-ubuntu
namespace: prometheus
chart: prometheus-community/prometheus
set:
- name: rbac.create
value: false
transformers:
# Use KCL Plugin to mutate or validate Kubernetes manifests.
- apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: "set-annotation"
annotations:
config.kubernetes.io/function: |
container:
image: docker.io/kcllang/kustomize-kcl:v0.2.0
spec:
source: |
[resource | {if resource.kind == "Deployment": metadata.annotations: {"managed-by" = "helmfile-kcl"}} for resource in option("resource_list").items]
In the above config, we use a KCLRun
plugin to assign the transfomer
field. This means that we will add annotations to all deployment resources in the prometheus helm chart.
2. Test and Run
Firstly, init the helmfile tool.
helmfile init
The output may looks like this:
The helm plugin helm-git is not installed, do you need to install it [y/n]: y
Install helm plugin helm-git
Installed plugin: helm-git
helmfile initialization completed!
...
Then apply the configuration.
helmfile apply
The output is
Adding repo prometheus-community https://prometheus-community.github.io/helm-charts
"prometheus-community" has been added to your repositories
...
Guides for Developing KCL
Here's what you can do in the KCL code:
- Read resources from
option("resource_list")
. Theoption("resource_list")
complies with the KRM Functions Specification. You can read the input resources fromoption("resource_list")["items"]
and thefunctionConfig
fromoption("resource_list")["functionConfig"]
. - Return a KPM list for output resources.
- Return an error using
assert {condition}, {error_message}
.