Functions - Crossplane

Functions extend Crossplane with new ways to configure [composition]({{<ref "../composition">}}).

You can use different composition functions to configure what Crossplane does when someone creates or updates a [composite resource (XR)]({{<ref "../composition/composite-resources">}}).

{{<hint "important">}} This page is a work in progress.

Functions are packages, like [Providers]({{<ref "./providers">}}) and [Configurations]({{<ref "./configurations">}}). Their APIs are similar. You install and configure them the same way as a provider.

Read the [composition]({{<ref "../composition/compositions">}}) documentation to learn how to use functions in a composition. {{</hint>}}

Install a function

Install a Function with a Crossplane {{<hover label="install" line="2">}}Function{{</hover >}} object setting the {{<hover label="install" line="6">}}spec.package{{</hover >}} value to the location of the function package.

For example, to install the patch and transform function,

yaml

apiVersion: pkg.crossplane.io/v1
kind: Function
metadata:
  name: crossplane-contrib-function-patch-and-transform
spec:
  package: xpkg.crossplane.io/crossplane-contrib/function-patch-and-transform:v0.8.2

By default, the Function pod installs in the same namespace as Crossplane (crossplane-system).

{{<hint "note" >}} Functions are part of the {{<hover label="install" line="1">}}pkg.crossplane.io{{</hover>}} group.

The {{<hover label="meta-pkg" line="1">}}meta.pkg.crossplane.io{{</hover>}} group is for creating Function packages.

Instructions on building Functions are outside of the scope of this document. Read the Crossplane contributing Function Development Guide for more information.

For information on the specification of Function packages read the Crossplane Function Package specification.

yaml

apiVersion: meta.pkg.crossplane.io/v1
kind: Function
metadata:
  name: provider-aws
spec:
# Removed for brevity