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Crossplane compositions

This directory hosts Crossplane Composite Resource Definitions (XRDs) and Compositions that this application provides to the platform — the inverse of the platform chart, which only consumes infrastructure.

Use this stack when your application exposes infrastructure capabilities that other applications can consume. For example, a Keycloak deployment might publish compositions that let other apps provision realms and clients via Claims.

Values reference: compositions/crossplane/

Structure​

compositions/crossplane/
├── xrd-<resource>.yaml           # CompositeResourceDefinition
├── composition-<resource>.yaml   # Composition (maps XRD to managed resources)
└── examples/
    └── claim-<resource>.yaml     # Example Claim for consumers

Keep one XRD + one Composition per logical resource. Split into separate files rather than bundling — Crossplane applies them independently, and diffs stay readable.

Install​

After adding compositions, apply them to the cluster:

kubectl apply -f compositions/crossplane/

Compositions are cluster-scoped — install them once per cluster, not per namespace.

Authoring a new composition​

  1. Define the XRD (xrd-<resource>.yaml) — the CRD-like schema consumers will write against. Keep the schema minimal; internal knobs belong in the Composition, not the Claim.
  2. Write the Composition (composition-<resource>.yaml) — maps XRD fields to one or more managed resources (e.g. a Keycloak Realm + a ClientRepresentation).
  3. Add an example Claim (examples/claim-<resource>.yaml) — a runnable demo consumers can copy.
  4. Test on a cluster — apply the XRD and Composition, then apply the example Claim. Verify the downstream managed resources reconcile before publishing.

Consuming compositions​

Other applications consume your XRDs by creating Claims in their platform Helm charts:

apiVersion: <your-group>/v1alpha1
kind: <YourClaimKind>
metadata:
  name: consumer-app-claim
spec:
  # fields defined by your XRD

Versioning​

  • Breaking changes to XRD schemas require a new API version (v1alpha2, v1beta1, etc.) — don't mutate v1alpha1 in place
  • Keep the previous version served alongside the new one until consumers migrate
  • Flag breaking changes in the application's CHANGELOG under a crossplane: prefix