When an instance cluster already exists migrate disabled

Assume that if an instance level cluster already exists, then the
KubernetesService was not being used, but allow the admin to re-enable
it if required

db/post_migrate/20190517153211_migrate_k8s_service_integration.rb

@@ -75,11 +75,13 @@ class MigrateK8sServiceIntegration < ActiveRecord::Migration[5.1]
   end
 
   def up
+    has_instance_cluster = Cluster.instance_type.where(enabled: true).exists?
+
     MigrateK8sServiceIntegration::Service.kubernetes_service_templates.find_each do |service|
       next unless service.api_url && service.token
 
       MigrateK8sServiceIntegration::Cluster.create!(
-        enabled: service.active,
+        enabled: !has_instance_cluster && service.active,
         managed: false,
         name: 'KubernetesService',
         cluster_type: 'instance_type',

spec/migrations/migrate_k8s_service_integration_spec.rb

@@ -104,6 +104,43 @@ describe MigrateK8sServiceIntegration, :migration do
         expect(platform.token).to eq('token-sample')
       end
     end
+
+    context 'when an instance cluster already exists' do
+      let!(:service) do
+        MigrateK8sServiceIntegration::Service.create!(
+          active: true,
+          template: true,
+          category: 'deployment',
+          type: 'KubernetesService',
+          properties: "{\"namespace\":\"prod\",\"api_url\":\"https://sample.kubernetes.com\",\"ca_pem\":\"ca_pem-sample\",\"token\":\"token-sample\"}"
+        )
+      end
+
+      let!(:existing_cluster) do
+        MigrateK8sServiceIntegration::Cluster.create!(
+          name: 'test-cluster',
+          cluster_type: :instance_type,
+          managed: true,
+          provider_type: :user,
+          platform_type: :kubernetes
+        )
+      end
+      let(:new_cluster) { MigrateK8sServiceIntegration::Cluster.instance_type.last! }
+      let(:platform) { new_cluster.platform_kubernetes }
+
+      it 'migrates the KubernetesService template to disabled Platform::Kubernetes' do
+        expect { migrate! }.to change { MigrateK8sServiceIntegration::Cluster.count }.by(1)
+
+        expect(new_cluster).not_to be_enabled
+        expect(new_cluster).to be_user
+        expect(new_cluster).not_to be_managed
+        expect(new_cluster.environment_scope).to eq('*')
+        expect(platform.api_url).to eq('https://sample.kubernetes.com')
+        expect(platform.ca_cert).to eq('ca_pem-sample')
+        expect(platform.namespace).to eq('prod')
+        expect(platform.token).to eq('token-sample')
+      end
+    end
   end
 
   context 'non-template service' do