github.com/GoogleContainerTools/kpt-functions-catalog/functions/go/render-helm-chart

render-helm-chart

Overview

The render-helm-chart function renders a local or remote Helm chart.

Helm is a package manager for kubernetes that uses a packaging format called charts. A chart is a collection of files within a directory, which contain templates, CRDs, values, and metadata.

This function renders charts by using the helm template command, so that helm charts can be rendered without needing to install the helm binary directly.

You can learn more about helm here and more about helm charts here.

Usage

This function can be used with any KRM function orchestrators such as kpt or kustomize to render a specified helm chart.

In kpt, the function can only be run imperatively. The function either needs network access to render a remote chart or needs a local file to be mounted into the container to render a local chart. As a result, to run the function with kpt fn eval, the flag --network must be used for remote charts, and the flag --mount must be used for local charts. See the examples for inflating local and remote charts.

It can be used declaratively when run with kustomize. To run the function with kustomize, the network field is needed for remote charts and the mounts field is needed for local charts. You can see an example of the former in the kustomize inline values example.

FunctionConfig

There are 2 kinds of functionConfig supported by this function:

• ConfigMap
• A custom resource of kind RenderHelmChart

Many of the fields in each functionConfig map directly to flag options provided by helm template.

ConfigMap

To use a ConfigMap as the functionConfig, the desired parameters must be specified in the data field:

data:
  chartHome: string
  configHome: string
  name: string
  version: string
  repo: string
  releaseName: string
  namespace: string
  nameTemplate: string
  includeCRDs: string
  skipTests: string
  valuesFile: string

RenderHelmChart

A functionConfig of kind RenderHelmChart has the following supported parameters:

helmGlobals:
  chartHome: string
  configHome: string
helmCharts:
- chartArgs: 
    name: string
    version: string
    repo: string
    registry: string
    auth:
      apiVersion: string (optional)
      kind: string
      name: string
      namespace: string (optional, default is "default")
  templateOptions:
    apiVersions: []string
    releaseName: string
    namespace: string
    nameTemplate: string
    includeCRDs: bool
    skipTests: bool
    values:
      valuesFiles: []string
      valuesInline: map[string]interface{}
      valuesMerge: string

functionConfig Field Descriptions and examples

Field	Description	Example
helmGlobals	Parameters applied to all Helm charts
helmCharts	An array of helm chart parameters
chartArgs	Arguments that describe the chart being rendered.
templateOptions	A collection of fields that map to flag options of helm template.
chartHome	A filepath to a directory of charts. The function will look for the chart in this local directory before attempting to pull the chart from a specified repo. Defaults to "tmp/charts". When run in a container, this path MUST have the prefix "tmp/".	tmp/charts
configHome	Defines a value that the function should pass to helm via the HELM_CONFIG_HOME environment variable.	/tmp/helm/config
name	The name of the chart.	minecraft
version	The version of the chart	3.1.3
repo	For remote charts, the URL locating the chart on the internet, equivalent to the --repo flag of helm pull.	https://itzg.github.io/minecraft-server-charts
registry	Necessary with private OCI registries. This is the URL if the OCI registry, and equivalent to the first argument <registry> in `helm registry login <registry>.	https://us-west2-docker.pkg.dev
auth	Necessary with private repos or registries. This field is the object reference of a Secret containing credentials in its data.username and data.password fields. The Secret must be passed into the function as part of the input ResourceList.
apiVersions	Kubernetes api versions used for Capabilities.APIVersions
releaseName	Replaces RELEASE_NAME in the chart template output	test
namespace	Sets the target namespace for a release (.Release.Namespace in the template)	my-namespace
nameTemplate	Specify the template used to name the release	gatekeeper
includeCRDs	Specifies if Helm should also generate CustomResourceDefinitions. Legal values: "true", "false" (default).	"true"
skipTests	If set, skip tests from templated output. Legal values: "true", "false" (default).	"true"
values	Values to use instead of the default values that accompany the chart. This can be defined inline or in a file.
valuesInline	Values defined inline to use instead of default values that accompany the chart	global:   enabled: false tests:   enabled: false
valuesFile	Remote or local filepath to use instead of the default values that accompanied the chart. The default values are in '{chartHome}/{name}/values.yaml', where chartHome and name are the parameters defined above.	Using a local values file: path/to/your/values.yaml Using a remote values file: https://raw.githubusercontent.com/config-sync-examples/helm-components/main/cert-manager-values.yaml
valuesFiles	Remote or local filepaths to use instead of the default values that accompanied the chart. The default values are in '{chartHome}/{name}/values.yaml', where chartHome and name are the parameters defined above.	Using a local values file: path/to/your/values.yaml Using a remote values file: https://raw.githubusercontent.com/config-sync-examples/helm-components/main/cert-manager-values.yaml
valuesMerge	ValuesMerge specifies how to treat ValuesInline with respect to ValuesFiles. Legal values: 'merge', 'override' (default), 'replace'.	replace

Examples

To render a remote minecraft chart, you can run the following command:

$ kpt fn eval --image gcr.io/kpt-fn/render-helm-chart:unstable --network -- \
name=minecraft \
repo=https://itzg.github.io/minecraft-server-charts \
releaseName=test

The key-value pairs after the -- will be converted to a functionConfig of kind ConfigMap. The above command will add two files to your directory, which you can view:

$ kpt pkg tree
├── [secret_test-minecraft.yaml]  Secret test-minecraft
└── [service_test-minecraft.yaml]  Service test-minecraft