scalvetr / poc-crossplane

POC Crossplane

This POC is a simple scenario with a REST api and a crossplane that call this API to synchronize the state defined in the CRDs (desired state) with the real state in the external service (real state).

• service-api: REST api all the operations related to a certain entity (topic)
• poc-crossplane-provider: a crossplane provider that synchronizes the state defined by CRDs to the external service (service-api).

You can find more information about Crossplane here

Prerequisites

• Install K8S local cluster with KinD
• Install Crossplane

Service API

The service API is written in Kotlin. For the sake of simplicity the persistence is in memory and no security is in place. Of course in a real scenario those aspects should be improved.

Find here the instructions to deploy it -> Deploy Service API

Crossplane provider

Crossplane provider has been based on the provider-template. Although I usually prefer a single repo per POC, in this case the code for the controller is in a separate repository: poc-crossplane-provider. That's because the provider-template offers a set of build scripts that relies on a rigid folder structure.

This provider has been writen in golang and uses a library service-client for the communication with service-api. This library is packaged along with the provider.

Find here the instrucations to deploy the crossplane provider

Deploy example

First we create a ProviderConfig in this case we set up the following parameters:

• api_url: url of the service. As the provider and the service are deployed in the same cluster, we'll use the internal url.
• tenant: it is a header that will be sent to the service
• credentials: credentials from the API. For now they are not used.

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Secret
metadata:
  namespace: crossplane-system
  name: example-provider-secret
type: Opaque
data:
  credentials: "c3VwZXItc2VjcmV0LXBhc3N3b3Jk"
---
apiVersion: poc.crossplane.io/v1alpha1
kind: ProviderConfig
metadata:
  name: tenant1
spec:
  api_url: "http://service-api.service-api:8080/v1"
  tenant: "tenant1"
  credentials:
    source: Secret
    secretRef:
      namespace: crossplane-system
      name: example-provider-secret
      key: credentials
EOF

# check the TENANT & API_URL
kubectl get providerconfigs.poc.crossplane.io

Once configured one tenant, we can start creating topics

cat <<EOF | kubectl create -f -
apiVersion: objects.poc.crossplane.io/v1alpha1
kind: Topic
metadata:
  name: topic1
spec:
  forProvider:
    name: topic1
    partitions: 5
  providerConfigRef:
    name: tenant1
EOF

# check the TOPIC_NAME, PARTITIONS & STATUS
kubectl get topics.objects.poc.crossplane.io

curl -k --header "x-tenant: tenant1" https://service-api.localtest.me/v1/topics
# [{"name":"topic1","partitions":5,"creationTime":"2022-06-20T23:18:29.067069508Z"}]

It can also be modified

cat <<EOF | kubectl apply -f -
apiVersion: objects.poc.crossplane.io/v1alpha1
kind: Topic
metadata:
  name: topic1
spec:
  forProvider:
    name: topic1
    partitions: 4
  providerConfigRef:
    name: tenant1
EOF
# topic.objects.poc.crossplane.io/topic1 configured

curl -k --header "x-tenant: tenant1" https://service-api.localtest.me/v1/topics/topic1
# {"name":"topic1","partitions":4,"creationTime":"2022-06-20T23:18:29.067069508Z"}

Other useful commands

# get the provider config
kubectl get providerconfig tenant1 -o yaml

# get desired status for topic1
kubectl get topic topic1 -o yaml

# get current status of topic1
curl -k --header "x-tenant: tenant1" https://service-api.localtest.me/v1/topics/topic1

# check service logs
kubectl -n service-api logs -l app=service-api 

https://service-api.localtest.me/actuator/swagger-ui.html