---
title: GCP Quickstart Part 2
weight: 120
tocHidden: true
aliases:
  - /master/getting-started/provider-azure-part-3
---

{{< 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.

{{< /hint >}}

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](https://cloud.google.com/storage) and a
  [Pub/Sub topic](https://cloud.google.com/pubsub).

{{<expand "Skip part 1 and just get started" >}}
1. Add the Crossplane Helm repository and install Crossplane.
```shell
helm repo add \
crossplane-stable https://charts.crossplane.io/stable
helm repo update
&&
helm install crossplane \
crossplane-stable/crossplane \
--namespace crossplane-system \
--create-namespace
```

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

```yaml {label="provider",copy-lines="all"}
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
```

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

{{< hint "tip" >}}
The
[GCP documentation](https://cloud.google.com/iam/docs/creating-managing-service-account-keys)
provides information on how to generate a service account JSON file.
{{< /hint >}}

4. Create a Kubernetes secret from the GCP JSON file
```shell {label="kube-create-secret",copy-lines="all"}
kubectl create secret \
generic gcp-secret \
-n crossplane-system \
--from-file=creds=./gcp-credentials.json
```

5. 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 >}}

{{< editCode >}}
```yaml {label="providerconfig",copy-lines="all"}
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
```
{{< /editCode >}}

{{</expand >}}

## 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.

```yaml
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`.

```shell {copy-lines="1"}
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

<!-- vale alex.Condescending = NO -->
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.
<!-- vale alex.Condescending = YES -->

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

```yaml {label="exAPI"}
apiVersion: database.example.com/v1alpha1
kind: NoSQL
metadata:
  name: my-nosql-database
spec:
  location: "US"
```

Like any Kubernetes object the API has a
{{<hover label="exAPI" line="1">}}version{{</hover>}},
{{<hover label="exAPI" line="2">}}kind{{</hover>}} and
{{<hover label="exAPI" line="5">}}spec{{</hover>}}.

### Define a group and version
To create your own API start by defining an
[API group](https://kubernetes.io/docs/reference/using-api/#api-groups) and
[version](https://kubernetes.io/docs/reference/using-api/#api-versioning).

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

<!-- vale gitlab.SentenceLength = NO -->
The version shows how mature or stable the API is and increments when changing,
adding or removing fields in the API.
<!-- vale gitlab.SentenceLength = YES -->

Crossplane doesn't require specific versions or a specific version naming
convention, but following
[Kubernetes API versioning guidelines](https://kubernetes.io/docs/reference/using-api/#api-versioning)
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
{{<hover label="version" line="1">}}database.example.com{{</hover>}}.

Because this is the first version of the API, this guide uses the version
{{<hover label="version" line="1">}}v1alpha1{{</hover>}}.

```yaml {label="version",copy-lines="none"}
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](https://kubernetes.io/docs/contribute/style/style-guide/#use-upper-camel-case-for-api-objects).

This API's kind is
{{<hover label="kind" line="2">}}PubSub{{</hover>}}

```yaml {label="kind",copy-lines="none"}
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
{{<hover label="spec" line="4">}}location{{</hover>}} 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.

```yaml {label="spec",copy-lines="none"}
apiVersion: queue.example.com/v1alpha1
kind: PubSub
spec:
  location: "US"
```

### Apply the API

Crossplane uses
{{<hover label="xrd" line="3">}}Composite Resource Definitions{{</hover>}}
(also called an `XRD`) to install your custom API in
Kubernetes.

The XRD {{<hover label="xrd" line="6">}}spec{{</hover>}} contains all the
information about the API including the
{{<hover label="xrd" line="7">}}group{{</hover>}},
{{<hover label="xrd" line="12">}}version{{</hover>}},
{{<hover label="xrd" line="9">}}kind{{</hover>}} and
{{<hover label="xrd" line="13">}}schema{{</hover>}}.

The XRD's {{<hover label="xrd" line="5">}}name{{</hover>}} must be the
combination of the {{<hover label="xrd" line="9">}}plural{{</hover>}} and
{{<hover label="xrd" line="7">}}group{{</hover>}}.

The {{<hover label="xrd" line="13">}}schema{{</hover>}} uses the
{{<hover label="xrd" line="14">}}OpenAPIv3{{</hover>}} specification to define
the API {{<hover label="xrd" line="17">}}spec{{</hover>}}.

The API defines a {{<hover label="xrd" line="20">}}location{{</hover>}} that
must be {{<hover label="xrd" line="22">}}oneOf{{</hover>}} either
{{<hover label="xrd" line="23">}}EU{{</hover>}} or
{{<hover label="xrd" line="24">}}US{{</hover>}}.

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

```yaml {label="xrd",copy-lines="all"}
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 {{<hover label="xrd" line="29">}}claimNames{{</hover>}} allows users
to access this API either at the cluster level with the
{{<hover label="xrd" line="9">}}pubsub{{</hover>}} endpoint or in a namespace
with the
{{<hover label="xrd" line="29">}}pubsubclaim{{</hover>}} 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`.

```shell {copy-lines="1"}
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`

```shell {copy-lines="1",label="apiRes"}
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 {{<hover label="comp" line="3">}}Composition{{</hover>}} 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
{{<hover label="comp" line="10">}}Storage{{</hover>}}
{{<hover label="comp" line="11">}}Bucket{{</hover>}} and a
{{<hover label="comp" line="25">}}PubSub{{</hover>}}
{{<hover label="comp" line="26">}}Topic{{</hover>}}.

This Composition takes the user's
{{<hover label="comp" line="16">}}location{{</hover>}} input and uses it as the
{{<hover label="comp" line="14">}}location{{</hover>}} 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.

```yaml {label="comp",copy-lines="all"}
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 {{<hover label="comp" line="40">}}compositeTypeRef{{</hover >}} 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
{{<hover label="comp" line="10">}}function-patch-and-transform{{</hover>}}.
You must install the function before you can use it in a Composition.

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

```yaml {label="install"}
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`

```shell {copy-lines="1"}
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 {{<hover label="xr" line="2">}}PubSub{{</hover>}} object to create the
cloud resources.

```yaml {copy-lines="all",label="xr"}
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`.

```shell {copy-lines="1"}
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`

```shell {copy-lines="1"}
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`.

```shell {copy-lines="1"}
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 >}}

```shell {copy-lines="1"}
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
{{<hover label="claim" line="3">}}kind{{</hover>}}
from the custom API's `claimNames`.

Create a new namespace to test create a Claim in.

```shell
kubectl create namespace crossplane-test
```

Then create a Claim in the `crossplane-test` namespace.

```yaml {label="claim",copy-lines="all"}
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`.

```shell {copy-lines="1"}
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`.

```shell {copy-lines="1"}
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`.

```shell {copy-lines="1"}
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`

```shell {copy-lines="1"}
kubectl delete pubsubclaim my-pubsub-queue -n crossplane-test
pubsubclaim.queue.example.com "my-pubsub-queue" deleted
```

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

Verify Crossplane deleted the composite resource with `kubectl get composite`.

```shell {copy-lines="1"}
kubectl get composite
No resources found
```

Verify Crossplane deleted the managed resources with `kubectl get managed`.

```shell {copy-lines="1"}
kubectl get managed
No resources found
```

## Next steps
* Explore AWS resources that Crossplane can configure in the
  [provider CRD reference](https://github.com/crossplane-contrib/provider-upjet-aws/blob/main/package/crds).
* Join the [Crossplane Slack](https://slack.crossplane.io/) and connect with
  Crossplane users and contributors.
* Read more about the [Crossplane concepts]({{<ref "../concepts">}}) to find out what else you can do
  with Crossplane.