Crossplane KCL function allows developers to use KCL (a DSL) to write composite logic without the need for repeated packaging of crossplane functions, and we support package management and the KRM KCL specification, which allows for OCI/Git source and the reuse of KCL's module ecosystem.
Check out this blog to learn more. Here's a simple example:
apiVersion: apiextensions.crossplane.io/v1
kind: Composition
metadata:
name: example
spec:
compositeTypeRef:
apiVersion: example.crossplane.io/v1beta1
kind: XR
mode: Pipeline
pipeline:
- step: basic
functionRef:
name: function-kcl
input:
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
source: |
# Read the XR
oxr = option("params").oxr
# Patch the XR with the status field
dxr = {
**oxr
status.dummy = "cool-status"
}
# Construct a bucket
bucket = {
apiVersion = "s3.aws.upbound.io/v1beta1"
kind = "Bucket"
metadata.annotations: {
"krm.kcl.dev/composition-resource-name" = "bucket"
}
spec.forProvider.region = option("oxr").spec.region
}
# Return the bucket and patched XR
items = [bucket, dxr]
- step: automatically-detect-ready-composed-resources
functionRef:
name: function-auto-readycat <<EOF | kubectl apply -f -
apiVersion: pkg.crossplane.io/v1beta1
kind: Function
metadata:
name: kcl-function
spec:
package: xpkg.upbound.io/crossplane-contrib/function-kcl:latest
EOFTo use a KCLRun as the function config, the KCL source must be specified in the source field. Additional parameters can be specified in the params field. The params field supports any complex data structure as long as it can be represented in YAML. Besides, the function can load KCL codes from inline source, OCI source, Git source and FileSystem source.
- Inline source example
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: |
{
apiVersion = "s3.aws.upbound.io/v1beta1"
kind = "Bucket"
metadata.annotations: {
"krm.kcl.dev/composition-resource-name" = "bucket"
}
spec.forProvider.region = option("oxr").spec.region
}- OCI source example
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: oci://ghcr.io/kcl-lang/crossplane-xnetwork-kcl-function- Git source example
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: github.com/kcl-lang/modules/crossplane-xnetwork-kcl-function- FileSystem source example
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: ./path/to/kcl/file.k- Read the
ObservedCompositeResourcefromoption("params").oxr. - Read the
ObservedComposedResourcesfromoption("params").ocds. - Read the
DesiredCompositeResourcefromoption("params").dxr. - Read the
DesiredComposedResourcesfromoption("params").dcds. - Read the
function pipeline's contextfromoption("params").ctx. - Return an error using
assert {condition}, {error_message}. - Log variable values using the function
print(variable)and it will be output to the stdout of the function pod. - Read the PATH variables. e.g.
option("PATH"). - Read the environment variables. e.g.
option("env").
You can define your custom parameters in the params field and use option("params").custom_key to get the custom_value.
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
params:
custom_key: custom_value
source: oci://ghcr.io/kcl-lang/crossplane-xnetwork-kcl-functionA KRM YAML list means that each document must have an apiVersion, kind through the items field or a single YAML output.
- Using the
itemsfield
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: |
items = [{
apiVersion: "ec2.aws.upbound.io/v1beta1"
kind: "Instance"
metadata.name = "instance1"
spec.forProvider.region: "us-east-2"
}, {
apiVersion: "ec2.aws.upbound.io/v1beta1"
kind: "Instance"
metadata.name = "instance2"
spec.forProvider.region: "us-east-2"
}]- Single YAML output
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: |
{
apiVersion: "ec2.aws.upbound.io/v1beta1"
kind: "Instance"
metadata.name = "instance"
spec.forProvider.ami: "ami-0d9858aa3c6322f73"
spec.forProvider.instanceType: "t2.micro"
spec.forProvider.region: "us-east-2"
}The KCL function can target various types of objects:
Default: create new resources and set fields on the XR.Resources: create new resources.PatchDesired: set fields on existing DesiredComposed Resources.PatchResources: set fields on existing resources fields. These resources will then be added to the desired resources map.XR: set fields on the XR.
This is controlled by fields on the KCLRun
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
# default: Default
target: Default | PatchDesired | PatchResources | Resources | XR
source: |
# Omit the source field
...To extract data from a specific composed resource by using the resource name, we can use the option("params").ocds variable, ocds is a mapping that its key is the resource name and its value is the observed composed resource like the example.
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: show-ocds
spec:
source: |
{
metadata.name = "ocds"
spec.ocds = option("params").ocds
spec.user_kind = option("params").ocds["test-user"]?.Resource.Kind
spec.user_metadata = option("params").ocds["test-user"]?.Resource.metadata
spec.user_status = option("params").ocds["test-user"]?.Resource.status
}To return desired composite resource connection details, include a KCL config that produces the special CompositeConnectionDetails resource like the example:
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: |
details = {
apiVersion: "meta.krm.kcl.dev/v1alpha1"
kind: "CompositeConnectionDetails"
data: {
"connection-secret-key": "connection-secret-value"
}
}
# Omit other composite logics.
# Input the details resource into the return resource list.
items = [
details
# Omit other return resources.
]Note: The value of the connection secret value must be base64 encoded. This is already the case if you are referencing a key from a managed resource's connectionDetails field. However, if you want to include a connection secret value from somewhere else, you will need to use the
base64.encodefunction:
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: |
import base64
# Omit other logic
ocds = option("params").ocds
details = {
apiVersion: "meta.krm.kcl.dev/v1alpha1"
kind: "CompositeConnectionDetails"
data: {
"server-endpoint" = base64.encode(ocds["my-server"].Resource.status.atProvider.endpoint)
}
}To mark a desired composed resource as ready, use the krm.kcl.dev/ready annotation:
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: |
# Omit other logic
user = {
apiVersion: "iam.aws.upbound.io/v1beta1"
kind: "User"
metadata.name = "test-user"
metadata.annotations: {
"krm.kcl.dev/ready": "True"
}
}You can read the XR, patch it with the status field and return the new patched XR in the item result like this
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: basic
spec:
source: |
# Read the XR
oxr = option("params").oxr
# Patch the XR with the status field
dxr = {
**oxr
status.dummy = "cool-status"
}
items = [dxr] # Omit other resourcesYou can directly use KCL standard libraries such as regex.match, math.log.
See here to study more features such as conditions and loops in KCL.
More examples can be found here
Logs are emitted to the Function's pod logs. Look for the Function pod in crossplane-system.
Info # default
Debug # run with --debug flag# Run code generation - see input/generate.go
$ go generate ./...
# Run tests - see fn_test.go
$ go test ./...
# Build the function's runtime image - see Dockerfile
$ docker build . --tag=kcllang/crossplane-kcl
# Build a function package - see package/crossplane.yaml
$ crossplane xpkg build -f package --embed-runtime-image=kcllang/crossplane-kcl
# Push a function package to the registry
$ crossplane --verbose xpkg push -f package/*.xpkg xpkg.upbound.io/crossplane-contrib/function-kcl:latest
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