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GCP Quickstart Part 2

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{{< hint "important" >}} This guide is part 2 of a series.

[Part 1]({{<ref "provider-gcp" >}}) covers to installing Crossplane and connect your Kubernetes cluster to GCP.

This guide walks you through building and accessing a custom API with Crossplane.

Prerequisites

Complete [quickstart part 1]({{<ref "provider-gcp" >}}) connecting Kubernetes to GCP.
a GCP account with permissions to create a GCP storage bucket and a Pub/Sub topic.

Add the Crossplane Helm repository and install Crossplane.

helm repo add \
crossplane-stable https://charts.crossplane.io/stable
helm repo update
&&
helm install crossplane \
crossplane-stable/crossplane \
--namespace crossplane-system \
--create-namespace

When the Crossplane pods finish installing and are ready, apply the GCP Provider.

cat <<EOF | kubectl apply -f -
apiVersion: pkg.crossplane.io/v1
kind: Provider
metadata:
  name: provider-gcp-storage
spec:
  package: xpkg.crossplane.io/crossplane-contrib/provider-gcp-storage:v1.12.1
EOF

Create a file called gcp-credentials.json with your GCP service account JSON file.

{{< hint "tip" >}} The GCP documentation provides information on how to generate a service account JSON file. {{< /hint >}}

Create a Kubernetes secret from the GCP JSON file

kubectl create secret \
generic gcp-secret \
-n crossplane-system \
--from-file=creds=./gcp-credentials.json

Create a ProviderConfig Include your {{< hover label="providerconfig" line="7" >}}GCP project ID{{< /hover >}} in the ProviderConfig settings.

{{< hint type="tip" >}} Find your GCP project ID from the project_id field of the gcp-credentials.json file. {{< /hint >}}

cat <<EOF | kubectl apply -f -
apiVersion: gcp.upbound.io/v1beta1
kind: ProviderConfig
metadata:
  name: default
spec:
  projectID: $@<PROJECT_ID>$@
  credentials:
    source: Secret
    secretRef:
      namespace: crossplane-system
      name: gcp-secret
      key: creds
EOF

{{}}

Install the PubSub Provider

Part 1 only installed the GCP Storage Provider. This section deploys a PubSub Topic along with a GCP storage bucket. First install the GCP PubSub Provider.

Add the new Provider to the cluster.

cat <<EOF | kubectl apply -f -
apiVersion: pkg.crossplane.io/v1
kind: Provider
metadata:
  name: provider-gcp-pubsub
spec:
  package: xpkg.crossplane.io/crossplane-contrib/provider-gcp-pubsub:v1.12.1
EOF

View the new PubSub provider with kubectl get providers.

kubectl get providers
NAME                                     INSTALLED   HEALTHY   PACKAGE                                                              AGE
crossplane-contrib-provider-family-gcp   True        True      xpkg.crossplane.io/crossplane-contrib/provider-family-gcp:v1.12.1    48m
provider-gcp-pubsub                      True        True      xpkg.crossplane.io/crossplane-contrib/provider-gcp-pubsub:v1.12.1    14s
provider-gcp-storage                     True        True      xpkg.crossplane.io/crossplane-contrib/provider-gcp-storage:v1.12.1   48m

Create a custom API

Crossplane allows you to build your own custom APIs for your users, abstracting away details about the cloud provider and their resources. You can make your API as complex or simple as you wish.

The custom API is a Kubernetes object. Here is an example custom API.

apiVersion: database.example.com/v1alpha1
kind: NoSQL
metadata:
  name: my-nosql-database
spec:
  location: "US"

Like any Kubernetes object the API has a {{}}version{{}}, {{}}kind{{}} and {{}}spec{{}}.

Define a group and version

To create your own API start by defining an API group and version.

The group can be any value, but common convention is to map to a fully qualified domain name.

The version shows how mature or stable the API is and increments when changing, adding or removing fields in the API.

Crossplane doesn't require specific versions or a specific version naming convention, but following Kubernetes API versioning guidelines is strongly recommended.

v1alpha1 - A new API that may change at any time.
v1beta1 - An existing API that's considered stable. Breaking changes are strongly discouraged.
v1 - A stable API that doesn't have breaking changes.

This guide uses the group {{}}database.example.com{{}}.

Because this is the first version of the API, this guide uses the version {{}}v1alpha1{{}}.

apiVersion: database.example.com/v1alpha1

Define a kind

The API group is a logical collection of related APIs. In a group are individual kinds representing different resources.

For example a queue group may have a PubSub and CloudTask kinds.

The kind can be anything, but it must be UpperCamelCased.

This API's kind is {{}}PubSub{{}}

apiVersion: queue.example.com/v1alpha1
kind: PubSub

Define a spec

The most important part of an API is the schema. The schema defines the inputs accepted from users.

This API allows users to provide a {{}}location{{}} of where to run their cloud resources.

All other resource settings can't be configurable by the users. This allows Crossplane to enforce any policies and standards without worrying about user errors.

apiVersion: queue.example.com/v1alpha1
kind: PubSub
spec:
  location: "US"

Apply the API

Crossplane uses {{}}Composite Resource Definitions{{}} (also called an XRD) to install your custom API in Kubernetes.

The XRD {{}}spec{{}} contains all the information about the API including the {{}}group{{}}, {{}}version{{}}, {{}}kind{{}} and {{}}schema{{}}.

The XRD's {{}}name{{}} must be the combination of the {{}}plural{{}} and {{}}group{{}}.

The {{}}schema{{}} uses the {{}}OpenAPIv3{{}} specification to define the API {{}}spec{{}}.

The API defines a {{}}location{{}} that must be {{}}oneOf{{}} either {{}}EU{{}} or {{}}US{{}}.

Apply this XRD to create the custom API in your Kubernetes cluster.

cat <<EOF | kubectl apply -f -
apiVersion: apiextensions.crossplane.io/v1
kind: CompositeResourceDefinition
metadata:
  name: pubsubs.queue.example.com
spec:
  group: queue.example.com
  names:
    kind: PubSub
    plural: pubsubs
  versions:
  - name: v1alpha1
    schema:
      openAPIV3Schema:
        type: object
        properties:
          spec:
            type: object
            properties:
              location:
                type: string
                oneOf:
                  - pattern: '^EU$'
                  - pattern: '^US$'
            required:
              - location
    served: true
    referenceable: true
  claimNames:
    kind: PubSubClaim
    plural: pubsubclaims
EOF

Adding the {{}}claimNames{{}} allows users to access this API either at the cluster level with the {{}}pubsub{{}} endpoint or in a namespace with the {{}}pubsubclaim{{}} endpoint.

The namespace scoped API is a Crossplane Claim.

{{<hint "tip" >}} For more details on the fields and options of Composite Resource Definitions read the [XRD documentation]({{<ref "../concepts/composite-resource-definitions">}}). {{< /hint >}}

View the installed XRD with kubectl get xrd.

kubectl get xrd
NAME                        ESTABLISHED   OFFERED   AGE
pubsubs.queue.example.com   True          True      7s

View the new custom API endpoints with kubectl api-resources | grep pubsub

kubectl api-resources | grep queue.example
pubsubclaims                 queue.example.com/v1alpha1             true         PubSubClaim
pubsubs                      queue.example.com/v1alpha1             false        PubSub

Create a deployment template

When users access the custom API Crossplane takes their inputs and combines them with a template describing what infrastructure to deploy. Crossplane calls this template a Composition.

The {{}}Composition{{}} defines all the cloud resources to deploy. Each entry in the template is a full resource definitions, defining all the resource settings and metadata like labels and annotations.

This template creates a GCP {{}}Storage{{}} {{}}Bucket{{}} and a {{}}PubSub{{}} {{}}Topic{{}}.

This Composition takes the user's {{}}location{{}} input and uses it as the {{}}location{{}} used in the individual resource.

{{<hint "important" >}} This Composition uses an array of resource templates. You can patch each template with data copied from the custom API. Crossplane calls this a Patch and Transform Composition.

You don't have to use Patch and Transform. Crossplane supports a variety of alternatives, including Go Templating and CUE. You can also write a function in Go or Python to template your resources.

Read the [Composition documentation]({{<ref "../concepts/compositions">}}) for more information on configuring Compositions and all the available options. {{< /hint >}}

Apply this Composition to your cluster.

cat <<EOF | kubectl apply -f -
apiVersion: apiextensions.crossplane.io/v1
kind: Composition
metadata:
  name: topic-with-bucket
spec:
  mode: Pipeline
  pipeline:
  - step: patch-and-transform
    functionRef:
      name: function-patch-and-transform
    input:
      apiVersion: pt.fn.crossplane.io/v1beta1
      kind: Resources
      resources:
        - name: crossplane-quickstart-bucket
          base:
            apiVersion: storage.gcp.upbound.io/v1beta1
            kind: Bucket
            spec:
              forProvider:
                location: "US"
          patches:
            - fromFieldPath: "spec.location"
              toFieldPath: "spec.forProvider.location"
              transforms:
                - type: map
                  map:
                    EU: "EU"
                    US: "US"
        - name: crossplane-quickstart-topic
          base:
            apiVersion: pubsub.gcp.upbound.io/v1beta1
            kind: Topic
            spec:
              forProvider:
                messageStoragePolicy:
                  - allowedPersistenceRegions:
                    - "us-central1"
          patches:
            - fromFieldPath: "spec.location"
              toFieldPath: "spec.forProvider.messageStoragePolicy[0].allowedPersistenceRegions[0]"
              transforms:
                - type: map
                  map:
                    EU: "europe-central2"
                    US: "us-central1"
  compositeTypeRef:
    apiVersion: queue.example.com/v1alpha1
    kind: PubSub
EOF

The {{}}compositeTypeRef{{}} defines which custom APIs can use this template to create resources.

A Composition uses a pipeline of composition functions to define the cloud resources to deploy. This template uses {{}}function-patch-and-transform{{}}. You must install the function before you can use it in a Composition.

Apply this Function to install function-patch-and-transform:

cat <<EOF | kubectl apply -f -
apiVersion: pkg.crossplane.io/v1
kind: Function
metadata:
  name: function-patch-and-transform
spec:
  package: xpkg.crossplane.io/crossplane-contrib/function-patch-and-transform:v0.8.2
EOF

{{<hint "tip" >}} Read the [Composition documentation]({{<ref "../concepts/compositions">}}) for more information on configuring Compositions and all the available options.

Read the [Patch and Transform function documentation]({{<ref "../guides/function-patch-and-transform">}}) for more information on how it uses patches to map user inputs to Composition resource templates. {{< /hint >}}

View the Composition with kubectl get composition

kubectl get composition
NAME                XR-KIND   XR-APIVERSION       AGE
topic-with-bucket   PubSub    queue.example.com   3s

Access the custom API

With the custom API (XRD) installed and associated to a resource template (Composition) users can access the API to create resources.

Create a {{}}PubSub{{}} object to create the cloud resources.

cat <<EOF | kubectl apply -f -
apiVersion: queue.example.com/v1alpha1
kind: PubSub
metadata:
  name: my-pubsub-queue
spec:
  location: "US"
EOF

View the resource with kubectl get pubsub.

kubectl get pubsub
NAME              SYNCED   READY   COMPOSITION         AGE
my-pubsub-queue   True     True    topic-with-bucket   2m12s

This object is a Crossplane composite resource (also called an XR). It's a single object representing the collection of resources created from the Composition template.

View the individual resources with kubectl get managed

kubectl get managed
NAME                                                READY   SYNCED   EXTERNAL-NAME           AGE
topic.pubsub.gcp.upbound.io/my-pubsub-queue-cjswx   True    True     my-pubsub-queue-cjswx   3m4s

NAME                                                  READY   SYNCED   EXTERNAL-NAME           AGE
bucket.storage.gcp.upbound.io/my-pubsub-queue-vljg9   True    True     my-pubsub-queue-vljg9   3m4s

Delete the resources with kubectl delete pubsub.

kubectl delete pubsub my-pubsub-queue
pubsub.queue.example.com "my-pubsub-queue" deleted

Verify Crossplane deleted the resources with kubectl get managed

{{<hint "note" >}} It may take up to 5 minutes to delete the resources. {{< /hint >}}

kubectl get managed
No resources found

Using the API with namespaces

Accessing the API pubsub happens at the cluster scope. Most organizations isolate their users into namespaces.

A Crossplane Claim is the custom API in a namespace.

Creating a Claim is just like accessing the custom API endpoint, but with the {{}}kind{{}} from the custom API's claimNames.

Create a new namespace to test create a Claim in.

kubectl create namespace crossplane-test

Then create a Claim in the crossplane-test namespace.

cat <<EOF | kubectl apply -f -
apiVersion: queue.example.com/v1alpha1
kind: PubSubClaim
metadata:
  name: my-pubsub-queue
  namespace: crossplane-test
spec:
  location: "US"
EOF

View the Claim with kubectl get claim -n crossplane-test.

kubectl get claim -n crossplane-test
NAME                SYNCED   READY   CONNECTION-SECRET   AGE
my-pubsub-queue   True     True                        2m10s

The Claim automatically creates a composite resource, which creates the managed resources.

View the Crossplane created composite resource with kubectl get composite.

kubectl get composite
NAME                    SYNCED   READY   COMPOSITION         AGE
my-pubsub-queue-7bm9n   True     True    topic-with-bucket   3m10s

Again, view the managed resources with kubectl get managed.

kubectl get managed
NAME                                                      READY   SYNCED   EXTERNAL-NAME                 AGE
topic.pubsub.gcp.upbound.io/my-pubsub-queue-7bm9n-6kdq4   True    True     my-pubsub-queue-7bm9n-6kdq4   3m22s

NAME                                                        READY   SYNCED   EXTERNAL-NAME                 AGE
bucket.storage.gcp.upbound.io/my-pubsub-queue-7bm9n-hhwx8   True    True     my-pubsub-queue-7bm9n-hhwx8   3m22s

Deleting the Claim deletes all the Crossplane generated resources.

kubectl delete claim -n crossplane-test my-pubsub-queue

kubectl delete pubsubclaim my-pubsub-queue -n crossplane-test
pubsubclaim.queue.example.com "my-pubsub-queue" deleted