Allow projects to use instance level clusters

There are two cluster hierarchies one for the deployment platform and
one for controllers. The main difference is that deployment platforms do
not check user permissions and only return the first match.

app/controllers/admin/clusters_controller.rb

@@ -8,10 +8,18 @@ class Admin::ClustersController < Clusters::ClustersController
   private
 
   def clusterable
-    @clusterable ||= InstanceClusterablePresenter.fabricate(Clusters::Instance.new, current_user: current_user)
+    @clusterable ||= InstanceClusterablePresenter.fabricate(cluster_instance, current_user: current_user)
+  end
+
+  def cluster_instance
+    @cluster_instance ||= Clusters::Instance.new
   end
 
   def check_instance_clusters_feature_flag!
-    render_404 unless Feature.enabled?(:instance_clusters, default_enabled: true)
+    render_404 unless instance_clusters_enabled?
+  end
+
+  def instance_clusters_enabled?
+    cluster_instance.instance_clusters_enabled?
   end
 end

app/models/clusters/cluster.rb

@@ -115,10 +115,12 @@ module Clusters
     }
 
     def self.ancestor_clusters_for_clusterable(clusterable, hierarchy_order: :asc)
+      return [] if clusterable.is_a?(Instance)
+
       hierarchy_groups = clusterable.ancestors_upto(hierarchy_order: hierarchy_order).eager_load(:clusters)
       hierarchy_groups = hierarchy_groups.merge(current_scope) if current_scope
 
-      hierarchy_groups.flat_map(&:clusters)
+      hierarchy_groups.flat_map(&:clusters) + Instance.new.clusters
     end
 
     def status_name

app/models/clusters/instance.rb

@@ -8,4 +8,8 @@ class Clusters::Instance
   def feature_available?(feature)
     ::Feature.enabled?(feature, default_enabled: true)
   end
+
+  def instance_clusters_enabled?
+    ::Feature.enabled?(:instance_clusters, default_enabled: true)
+  end
 end

app/models/concerns/deployment_platform.rb

@@ -14,6 +14,7 @@ module DeploymentPlatform
   def find_deployment_platform(environment)
     find_cluster_platform_kubernetes(environment: environment) ||
       find_group_cluster_platform_kubernetes_with_feature_guard(environment: environment) ||
+      find_instance_cluster_platform_kubernetes_with_feature_guard(environment: environment) ||
       find_kubernetes_service_integration ||
       build_cluster_and_deployment_platform
   end
@@ -36,6 +37,22 @@ module DeploymentPlatform
       .first&.platform_kubernetes
   end
 
+  def find_instance_cluster_platform_kubernetes_with_feature_guard(environment: nil)
+    return unless instance_clusters_enabled?
+
+    find_instance_cluster_platform_kubernetes(environment: environment)
+  end
+
+  # EE would override this and utilize environment argument
+  def find_instance_cluster_platform_kubernetes(environment: nil)
+    Clusters::Instance.new.clusters.enabled.default_environment
+      .first&.platform_kubernetes
+  end
+
+  def instance_clusters_enabled?
+    Feature.enabled?(:instance_clusters, default_enabled: true)
+  end
+
   def find_kubernetes_service_integration
     services.deployment.reorder(nil).find_by(active: true)
   end

spec/finders/cluster_ancestors_finder_spec.rb

@@ -8,11 +8,15 @@ describe ClusterAncestorsFinder, '#execute' do
   let(:user) { create(:user) }
 
   let!(:project_cluster) do
-    create(:cluster, :provided_by_user, cluster_type: :project_type, projects: [project])
+    create(:cluster, :provided_by_user, :project, projects: [project])
   end
 
   let!(:group_cluster) do
-    create(:cluster, :provided_by_user, cluster_type: :group_type, groups: [group])
+    create(:cluster, :provided_by_user, :group, groups: [group])
+  end
+
+  let!(:instance_cluster) do
+    create(:cluster, :provided_by_user, :instance)
   end
 
   subject { described_class.new(clusterable, user).execute }
@@ -25,7 +29,7 @@ describe ClusterAncestorsFinder, '#execute' do
     end
 
     it 'returns the project clusters followed by group clusters' do
-      is_expected.to eq([project_cluster, group_cluster])
+      is_expected.to eq([project_cluster, group_cluster, instance_cluster])
     end
 
     context 'nested groups', :nested_groups do
@@ -33,11 +37,11 @@ describe ClusterAncestorsFinder, '#execute' do
       let(:parent_group) { create(:group) }
 
       let!(:parent_group_cluster) do
-        create(:cluster, :provided_by_user, cluster_type: :group_type, groups: [parent_group])
+        create(:cluster, :provided_by_user, :group, groups: [parent_group])
       end
 
       it 'returns the project clusters followed by group clusters ordered ascending the hierarchy' do
-        is_expected.to eq([project_cluster, group_cluster, parent_group_cluster])
+        is_expected.to eq([project_cluster, group_cluster, parent_group_cluster, instance_cluster])
       end
     end
   end
@@ -58,7 +62,7 @@ describe ClusterAncestorsFinder, '#execute' do
     end
 
     it 'returns the list of group clusters' do
-      is_expected.to eq([group_cluster])
+      is_expected.to eq([group_cluster, instance_cluster])
     end
 
     context 'nested groups', :nested_groups do
@@ -66,12 +70,21 @@ describe ClusterAncestorsFinder, '#execute' do
       let(:parent_group) { create(:group) }
 
       let!(:parent_group_cluster) do
-        create(:cluster, :provided_by_user, cluster_type: :group_type, groups: [parent_group])
+        create(:cluster, :provided_by_user, :group, groups: [parent_group])
       end
 
       it 'returns the list of group clusters ordered ascending the hierarchy' do
-        is_expected.to eq([group_cluster, parent_group_cluster])
+        is_expected.to eq([group_cluster, parent_group_cluster, instance_cluster])
+      end
     end
   end
+
+  context 'for an instance' do
+    let(:clusterable) { Clusters::Instance.new }
+    let(:user) { create(:admin) }
+
+    it 'returns the list of instance clusters' do
+      is_expected.to eq([instance_cluster])
+    end
   end
 end

spec/models/clusters/cluster_spec.rb

@@ -325,6 +325,15 @@ describe Clusters::Cluster do
       end
     end
 
+    context 'when group and instance have configured kubernetes clusters' do
+      let(:project) { create(:project, group: group) }
+      let!(:instance_cluster) { create(:cluster, :provided_by_gcp, :instance) }
+
+      it 'returns clusters in order, descending the hierachy' do
+        is_expected.to eq([group_cluster, instance_cluster])
+      end
+    end
+
     context 'when sub-group has configured kubernetes cluster', :nested_groups do
       let(:sub_group_cluster) { create(:cluster, :provided_by_gcp, :group) }
       let(:sub_group) { sub_group_cluster.group }

spec/policies/clusters/instance_policy_spec.rb

@@ -9,6 +9,7 @@ describe Clusters::InstancePolicy do
 
   describe 'rules' do
     context 'when user' do
+      it { expect(policy).to be_disallowed :read_cluster }
       it { expect(policy).to be_disallowed :update_cluster }
       it { expect(policy).to be_disallowed :admin_cluster }
     end
@@ -16,6 +17,7 @@ describe Clusters::InstancePolicy do
     context 'when admin' do
       let(:user) { create(:admin) }
 
+      it { expect(policy).to be_allowed :read_cluster }
       it { expect(policy).to be_allowed :update_cluster }
       it { expect(policy).to be_allowed :admin_cluster }
     end