Claims

Once we've configured Crossplane with the details of the new XR, we can either create one directly or use a Claim. Typically, only the team responsible for configuring Crossplane (often a platform or SRE team) has permission to create XRs directly. Everyone else manages XRs via a lightweight proxy resource called a Composite Resource Claim (or claim for short).

With this claim, the developer only needs to specify a default DynamoDB table name, hash keys, and global index name to create the table. This allows the platform or SRE team to standardize aspects such as billing mode, default read/write capacity, projection type, and cost and infrastructure-related tags.

~/environment/eks-workshop/modules/automation/controlplanes/crossplane/compositions/claim/claim.yaml

apiVersion: awsblueprints.io/v1alpha1
kind: DynamoDBTable
metadata:
  name: "${EKS_CLUSTER_NAME}-carts-crossplane"
spec:
  dynamoConfig:
    attribute:
      - name: id
        type: S
      - name: customerId
        type: S
    globalSecondaryIndex:
      - name: idx_global_customerId

Let's start by cleaning up the DynamoDB table created in the previous Managed Resource section:

~$kubectl delete tables.dynamodb.aws.upbound.io --all --ignore-not-found=true

~$kubectl wait --for=delete tables.dynamodb.aws.upbound.io --all --timeout=5m

Now, we can re-create the table by creating a Claim:

~$cat ~/environment/eks-workshop/modules/automation/controlplanes/crossplane/compositions/claim/claim.yaml \

| envsubst | kubectl -n carts apply -f -

dynamodbtable.awsblueprints.io/eks-workshop-carts-crossplane created

~$kubectl wait dynamodbtables.awsblueprints.io ${EKS_CLUSTER_NAME}-carts-crossplane -n carts \

--for=condition=Ready --timeout=5m

It takes some time to provision AWS managed services, in the case of DynamoDB up to 2 minutes. Crossplane will report the status of the reconciliation in the SYNCED field of the Kubernetes Composite and Managed resource.

~$kubectl get table

NAME                                        READY   SYNCED   EXTERNAL-NAME                   AGE

eks-workshop-carts-crossplane-bt28w-lnb4r   True   True      eks-workshop-carts-crossplane   6s

Now, let's understand how the DynamoDB table is deployed using this claim:

When querying the claim DynamoDBTable deployed in the carts namespace, we can observe that it points to and creates a Composite Resource (XR) XDynamoDBTable:

~$kubectl get DynamoDBTable -n carts -o yaml | grep "resourceRef:" -A 3

    resourceRef:

      apiVersion: awsblueprints.io/v1alpha1

      kind: XDynamoDBTable

      name: eks-workshop-carts-crossplane-bt28w

The Composition table.dynamodb.awsblueprints.io shows Composite Resource Kind (XR-KIND) as XDynamoDBTable. This Composition informs Crossplane what to do when we create the XDynamoDBTable XR. Each Composition creates a link between an XR and a set of one or more Managed Resources.

~$kubectl get composition

NAME                              XR-KIND          XR-APIVERSION               AGE

table.dynamodb.awsblueprints.io   XDynamoDBTable   awsblueprints.io/v1alpha1   143m

When querying the XDynamoDBTable XR, which is not confined to any namespace, we can observe that it creates a DynamoDB managed resource Table:

~$kubectl get XDynamoDBTable -o yaml | grep "resourceRefs:" -A 3

    resourceRefs:

    - apiVersion: dynamodb.aws.upbound.io/v1beta1

      kind: Table

      name: eks-workshop-carts-crossplane-bt28w-lnb4r