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demo-xfn-creds

This is a demo function that shows how to use credentials/secrets in your composition functions. The composition has a reference to a credentials secret, and the function machinery securely passes this data to the function. Then the function uses these credentials to connect to AWS and list all the available EC2 instance types for the region. If the requested instance type from the composition is not "current generation", then the function will return an error and the EC2 instance from the composition will not be created.

General information about credentials/secrets support in Crossplane can be found in issue #3718 and PR #5543.

Pre-Requisites

  1. A Kubernetes cluster with Crossplane v1.16.0+ installed

Set-up

First, cd into the example directory:

cd example

Install all the required functions and providers:

kubectl apply -f functions.yaml
kubectl apply -f providers.yaml

And make sure they become installed and healthy:

kubectl get pkg

Create the AWS credentials that will be used by both the function and the AWS provider:

AWS_PROFILE=default && echo -e "[default]\naws_access_key_id = $(aws configure get aws_access_key_id --profile $AWS_PROFILE)\naws_secret_access_key = $(aws configure get aws_secret_access_key --profile $AWS_PROFILE)" > aws-creds.txt

kubectl create secret generic aws-creds -n crossplane-system --from-file=credentials=./aws-creds.txt

kubectl apply -f aws-default-provider.yaml

Apply the CompositeResourceDefinition (XRD) and Composition:

kubectl apply -f definition.yaml
kubectl apply -f composition.yaml

Now we are ready to create a compute instance:

kubectl apply -f claim.yaml

Since we have provided an old non-current generation instance type, we expect the function to return an error and refuse to create the instance:

crossplane beta trace compute.example.crossplane.io/dev-instance -o wide
kubectl describe compute.example.crossplane.io/dev-instance

Let's update the instance type to a value that is current generation (t3.micro) and try again:

# edit claim.yaml to change instanceType to t3.micro, then:
kubectl apply -f claim.yaml

Now we should be using a current generation instance type, let's examine the claim again:

crossplane beta trace compute.example.crossplane.io/dev-instance -o wide

Great, it's creating the EC2 instance now. Let's examine that managed resource too:

kubectl get instance.ec2 -l crossplane.io/claim-name=dev-instance

Cool! Our function made authenticated requests to AWS, using the credentials we supplied from our composition, to check if the requested instance type is current generation or not, and then only allowed current generation instances to be created.

Now we have seen how to use credentials/secrets in your composition functions! ✅

Clean-up

Make sure to clean-up the EC2 instance by deleting the claim:

kubectl delete -f claim.yaml
kubectl get instance.ec2

Building and pushing

If you want to build and push this function yourself, you can use commands similar to the below, taken from the Crossplane docs guide on building a function in Go:

Build the runtime images:

docker build . --quiet --platform=linux/amd64 --tag runtime-amd64
docker build . --quiet --platform=linux/arm64 --tag runtime-arm64

Build the Crossplane packages:

crossplane xpkg build \
    --package-root=package \
    --embed-runtime-image=runtime-amd64 \
    --package-file=function-amd64.xpkg
crossplane xpkg build \
    --package-root=package \
    --embed-runtime-image=runtime-arm64 \
    --package-file=function-arm64.xpkg

Push to the marketplace registry:

crossplane xpkg push \
  --package-files=function-amd64.xpkg,function-arm64.xpkg \
  jaredorg/demo-xfn-creds:v0.0.1