crossplane-function-extra-resources

packaged by Chainguard

Chainguard Container for crossplane-function-extra-resources

This composition function retrieves existing cluster resources by name or label selector and adds them to the Crossplane composition pipeline context.

Chainguard Containers are regularly-updated, secure-by-default container images.

Download this Container Image

For those with access, this container image is available on cgr.dev:

docker pull cgr.dev/ORGANIZATION/crossplane-function-extra-resources:latest

Be sure to replace the ORGANIZATION placeholder with the name used for your organization's private repository within the Chainguard Registry.

Compatibility Notes

The Chainguard crossplane-function-extra-resources container image is a drop-in replacement for the upstream function-extra-resources Crossplane package published at xpkg.upbound.io/crossplane-contrib/function-extra-resources. The image ships the function binary together with the Crossplane package metadata and the Input CRD in /package.yaml, so you can reference it directly in a Function resource. Like the upstream image, it uses /function as the entrypoint and runs as the nonroot user with UID 65532.

Prerequisites

You need a Kubernetes cluster with Crossplane v2.0 or later installed. If Crossplane is not installed yet, install it with Helm:

helm repo add crossplane-stable https://charts.crossplane.io/stable
helm repo update
helm install crossplane --namespace crossplane-system --create-namespace crossplane-stable/crossplane

Getting Started

Create a Function resource that points at the Chainguard image:

cat > function.yaml <<EOF
apiVersion: pkg.crossplane.io/v1
kind: Function
metadata:
  name: function-extra-resources
spec:
  package: cgr.dev/ORGANIZATION/crossplane-function-extra-resources:latest
EOF
kubectl apply -f function.yaml

Wait for Crossplane to install the function and report it as healthy:

kubectl wait --for=condition=Healthy function.pkg.crossplane.io/function-extra-resources --timeout=300s

Configuration

function-extra-resources does not change resources itself. It fetches existing resources and places them in the pipeline context under the apiextensions.crossplane.io/extra-resources key, where a later step such as function-go-templating can read them.

The following Composition step selects every EnvironmentConfig labeled type: cluster and stores the matches under the clusters key:

pipeline:
  - step: pull-extra-resources
    functionRef:
      name: function-extra-resources
    input:
      apiVersion: extra-resources.fn.crossplane.io/v1beta1
      kind: Input
      spec:
        extraResources:
          - kind: EnvironmentConfig
            apiVersion: apiextensions.crossplane.io/v1beta1
            into: clusters
            type: Selector
            selector:
              minMatch: 1
              maxMatch: 5
              matchLabels:
                - key: type
                  type: Value
                  value: cluster

Set minMatch so the composition fails fast when a required resource is missing, and maxMatch to bound how many resources the step passes on. To fetch a single resource by name instead, use type: Reference together with ref.name. Matches are sorted by metadata.name unless you set selector.sortByFieldPath.

A downstream go-templating step can then read the selected resources from the context. This step writes their names into the status of an XLookup composite resource:

  - step: render
    functionRef:
      name: function-go-templating
    input:
      apiVersion: gotemplating.fn.crossplane.io/v1beta1
      kind: GoTemplate
      source: Inline
      inline:
        template: |
          {{- $clusters := index (index .context "apiextensions.crossplane.io/extra-resources") "clusters" }}
          apiVersion: example.io/v1alpha1
          kind: XLookup
          status:
            matched: {{ len $clusters }}
            names: "{{ range $i, $c := $clusters }}{{ if $i }},{{ end }}{{ $c.metadata.name }}{{ end }}"

Documentation and Resources

• function-extra-resources on GitHub
• Crossplane composition functions
• Crossplane EnvironmentConfigs

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Trademarks

This software listing is packaged by Chainguard. The trademarks set forth in this offering are owned by their respective companies, and use of them does not imply any affiliation, sponsorship, or endorsement by such companies.