This composition function automatically detects composed resources that are ready. It considers a composed resource ready if:

• Another function added the composed resource to the desired state.
• The composed resource appears in the observed state (i.e. it exists).
• The composed resource has the status condition type: Ready, status: True.

Crossplane considers a composite resource (XR) to be ready when all of its desired composed resources are ready.

In this example, the Go Templating function is used to add a desired composed resource - an Amazon Web Services S3 Bucket. Once Crossplane has created the Bucket, the Auto Ready function will let Crossplane know when it is ready. Because this XR only has one composed resource, the XR will become ready when the Bucket becomes ready.

apiVersion: apiextensions.crossplane.io/v1
kind: Composition
metadata:
  name: example
spec:
  compositeTypeRef:
    apiVersion: example.crossplane.io/v1beta1
    kind: XR
  mode: Pipeline
  pipeline:
  - step: create-a-bucket
    functionRef:
      name: function-go-templating
    input:
      apiVersion: gotemplating.fn.crossplane.io/v1beta1
      kind: GoTemplate
      source: Inline
      inline:
        template: |
          apiVersion: s3.aws.upbound.io/v1beta1
          kind: Bucket
          metadata:
            annotations:
              gotemplating.fn.crossplane.io/composition-resource-name: bucket
          spec:
            forProvider:
              region: {{ .observed.composite.resource.spec.region }}
  - step: automatically-detect-ready-composed-resources
    functionRef:
      name: function-auto-ready

See the example directory for an example you can run locally using the Crossplane CLI:

$ crossplane beta render xr.yaml composition.yaml functions.yaml

See the composition functions documentation to learn more about crossplane beta render.

This function uses Go, Docker, and the Crossplane CLI to build functions.

# 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=runtime

# Build a function package - see package/crossplane.yaml
$ crossplane xpkg build -f package --embed-runtime-image=runtime