Associate clusters model to groups

Even though we currently only should have one group for a cluster, we
allow the flexibility to associate to other groups in the future.

This also matches the runner <=> groups association.

- Adds Cluster#first_group, aliased to Cluster#group. For the
conceivable future, a cluster will have at most one group.

- Prevent mixing of group and project clusters. If project type
clusters, it should only have projects assigned.  Similarly with groups.

- Default cluster_type to :project_type. As it's very small table we can
set default and null: false in one release.

app/models/clusters/cluster.rb

@@ -20,6 +20,12 @@ module Clusters
     has_many :cluster_projects, class_name: 'Clusters::Project'
     has_many :projects, through: :cluster_projects, class_name: '::Project'
 
+    has_many :cluster_groups, class_name: 'Clusters::Group'
+    has_many :groups, through: :cluster_groups, class_name: '::Group'
+
+    has_one :cluster_group, -> { order(id: :desc) }, class_name: 'Clusters::Group'
+    has_one :group, through: :cluster_group, class_name: '::Group'
+
     # we force autosave to happen when we save `Cluster` model
     has_one :provider_gcp, class_name: 'Clusters::Providers::Gcp', autosave: true
 
@@ -38,8 +44,12 @@ module Clusters
     accepts_nested_attributes_for :platform_kubernetes, update_only: true
 
     validates :name, cluster_name: true
+    validates :cluster_type, presence: true
     validate :restrict_modification, on: :update
 
+    validate :no_groups, unless: :group_type?
+    validate :no_projects, unless: :project_type?
+
     delegate :status, to: :provider, allow_nil: true
     delegate :status_reason, to: :provider, allow_nil: true
     delegate :on_creation?, to: :provider, allow_nil: true
@@ -50,6 +60,12 @@ module Clusters
     delegate :available?, to: :application_ingress, prefix: true, allow_nil: true
     delegate :available?, to: :application_prometheus, prefix: true, allow_nil: true
 
+    enum cluster_type: {
+      instance_type: 1,
+      group_type: 2,
+      project_type: 3
+    }
+
     enum platform_type: {
       kubernetes: 1
     }
@@ -122,5 +138,17 @@ module Clusters
 
       true
     end
+
+    def no_groups
+      if groups.any?
+        errors.add(:cluster, 'cannot have groups assigned')
+      end
+    end
+
+    def no_projects
+      if projects.any?
+        errors.add(:cluster, 'cannot have projects assigned')
+      end
+    end
   end
 end

app/models/clusters/group.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+module Clusters
+  class Group < ActiveRecord::Base
+    self.table_name = 'cluster_groups'
+
+    belongs_to :cluster, class_name: 'Clusters::Cluster'
+    belongs_to :group, class_name: '::Group'
+  end
+end

app/models/concerns/deployment_platform.rb

@@ -42,6 +42,7 @@ module DeploymentPlatform
     {
       name: 'kubernetes-template',
       projects: [self],
+      cluster_type: :project_type,
       provider_type: :user,
       platform_type: :kubernetes,
       platform_kubernetes_attributes: platform_kubernetes_attributes_from_service_template

app/models/group.rb

@@ -41,6 +41,9 @@ class Group < Namespace
   has_many :boards
   has_many :badges, class_name: 'GroupBadge'
 
+  has_many :cluster_groups, class_name: 'Clusters::Group'
+  has_many :clusters, through: :cluster_groups, class_name: 'Clusters::Cluster'
+
   has_many :todos
 
   accepts_nested_attributes_for :variables, allow_destroy: true

app/services/clusters/create_service.rb

@@ -9,9 +9,9 @@ module Clusters
     end
 
     def execute(project:, access_token: nil)
-      raise ArgumentError.new(_('Instance does not support multiple Kubernetes clusters')) unless can_create_cluster?(project)
+      raise ArgumentError, _('Instance does not support multiple Kubernetes clusters') unless can_create_cluster?(project)
 
-      cluster_params = params.merge(user: current_user, projects: [project])
+      cluster_params = params.merge(user: current_user, cluster_type: :project_type, projects: [project])
       cluster_params[:provider_gcp_attributes].try do |provider|
         provider[:access_token] = access_token
       end

changelogs/unreleased/34758-create-group-clusters.yml

@@ -0,0 +1,5 @@
+---
+title: Adds model and migrations to enable group level clusters
+merge_request: 22307
+author:
+type: other

db/migrate/20181014203236_create_cluster_groups.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class CreateClusterGroups < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def change
+    create_table :cluster_groups do |t|
+      t.references :cluster, null: false, foreign_key: { on_delete: :cascade }
+      t.references :group, null: false, index: true
+
+      t.index [:cluster_id, :group_id], unique: true
+      t.foreign_key :namespaces, column: :group_id, on_delete: :cascade
+    end
+  end
+end

db/migrate/20181017001059_add_cluster_type_to_clusters.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class AddClusterTypeToClusters < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  PROJECT_CLUSTER_TYPE = 3
+
+  disable_ddl_transaction!
+
+  def up
+    add_column_with_default(:clusters, :cluster_type, :smallint, default: PROJECT_CLUSTER_TYPE)
+  end
+
+  def down
+    remove_column(:clusters, :cluster_type)
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20181016152238) do
+ActiveRecord::Schema.define(version: 20181017001059) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -599,6 +599,14 @@ ActiveRecord::Schema.define(version: 20181016152238) do
 
   add_index "ci_variables", ["project_id", "key", "environment_scope"], name: "index_ci_variables_on_project_id_and_key_and_environment_scope", unique: true, using: :btree
 
+  create_table "cluster_groups", force: :cascade do |t|
+    t.integer "cluster_id", null: false
+    t.integer "group_id", null: false
+  end
+
+  add_index "cluster_groups", ["cluster_id", "group_id"], name: "index_cluster_groups_on_cluster_id_and_group_id", unique: true, using: :btree
+  add_index "cluster_groups", ["group_id"], name: "index_cluster_groups_on_group_id", using: :btree
+
   create_table "cluster_platforms_kubernetes", force: :cascade do |t|
     t.integer "cluster_id", null: false
     t.datetime_with_timezone "created_at", null: false
@@ -654,6 +662,7 @@ ActiveRecord::Schema.define(version: 20181016152238) do
     t.boolean "enabled", default: true
     t.string "name", null: false
     t.string "environment_scope", default: "*", null: false
+    t.integer "cluster_type", limit: 2, default: 3, null: false
   end
 
   add_index "clusters", ["enabled"], name: "index_clusters_on_enabled", using: :btree
@@ -2372,6 +2381,8 @@ ActiveRecord::Schema.define(version: 20181016152238) do
   add_foreign_key "ci_triggers", "projects", name: "fk_e3e63f966e", on_delete: :cascade
   add_foreign_key "ci_triggers", "users", column: "owner_id", name: "fk_e8e10d1964", on_delete: :cascade
   add_foreign_key "ci_variables", "projects", name: "fk_ada5eb64b3", on_delete: :cascade
+  add_foreign_key "cluster_groups", "clusters", on_delete: :cascade
+  add_foreign_key "cluster_groups", "namespaces", column: "group_id", on_delete: :cascade
   add_foreign_key "cluster_platforms_kubernetes", "clusters", on_delete: :cascade
   add_foreign_key "cluster_projects", "clusters", on_delete: :cascade
   add_foreign_key "cluster_projects", "projects", on_delete: :cascade

spec/factories/clusters/clusters.rb

@@ -2,13 +2,28 @@ FactoryBot.define do
   factory :cluster, class: Clusters::Cluster do
     user
     name 'test-cluster'
+    cluster_type :project_type
+
+    trait :instance do
+      cluster_type { Clusters::Cluster.cluster_types[:instance_type] }
+    end
 
     trait :project do
+      cluster_type { Clusters::Cluster.cluster_types[:project_type] }
+
       before(:create) do |cluster, evaluator|
         cluster.projects << create(:project, :repository)
       end
     end
 
+    trait :group do
+      cluster_type { Clusters::Cluster.cluster_types[:group_type] }
+
+      before(:create) do |cluster, evalutor|
+        cluster.groups << create(:group)
+      end
+    end
+
     trait :provided_by_user do
       provider_type :user
       platform_type :kubernetes

spec/models/clusters/cluster_spec.rb

@@ -4,7 +4,10 @@ require 'spec_helper'
 
 describe Clusters::Cluster do
   it { is_expected.to belong_to(:user) }
+  it { is_expected.to have_many(:cluster_projects) }
   it { is_expected.to have_many(:projects) }
+  it { is_expected.to have_many(:cluster_groups) }
+  it { is_expected.to have_many(:groups) }
   it { is_expected.to have_one(:provider_gcp) }
   it { is_expected.to have_one(:platform_kubernetes) }
   it { is_expected.to have_one(:application_helm) }
@@ -178,6 +181,53 @@ describe Clusters::Cluster do
         it { expect(cluster.update(enabled: false)).to be_truthy }
       end
     end
+
+    describe 'cluster_type validations' do
+      let(:instance_cluster) { create(:cluster, :instance) }
+      let(:group_cluster) { create(:cluster, :group) }
+      let(:project_cluster) { create(:cluster, :project) }
+
+      it 'validates presence' do
+        cluster = build(:cluster, :project, cluster_type: nil)
+
+        expect(cluster).not_to be_valid
+        expect(cluster.errors.full_messages).to include("Cluster type can't be blank")
+      end
+
+      context 'project_type cluster' do
+        it 'does not allow setting group' do
+          project_cluster.groups << build(:group)
+
+          expect(project_cluster).not_to be_valid
+          expect(project_cluster.errors.full_messages).to include('Cluster cannot have groups assigned')
+        end
+      end
+
+      context 'group_type cluster' do
+        it 'does not allow setting project' do
+          group_cluster.projects << build(:project)
+
+          expect(group_cluster).not_to be_valid
+          expect(group_cluster.errors.full_messages).to include('Cluster cannot have projects assigned')
+        end
+      end
+
+      context 'instance_type cluster' do
+        it 'does not allow setting group' do
+          instance_cluster.groups << build(:group)
+
+          expect(instance_cluster).not_to be_valid
+          expect(instance_cluster.errors.full_messages).to include('Cluster cannot have groups assigned')
+        end
+
+        it 'does not allow setting project' do
+          instance_cluster.projects << build(:project)
+
+          expect(instance_cluster).not_to be_valid
+          expect(instance_cluster.errors.full_messages).to include('Cluster cannot have projects assigned')
+        end
+      end
+    end
   end
 
   describe '#provider' do
@@ -229,6 +279,23 @@ describe Clusters::Cluster do
     end
   end
 
+  describe '#group' do
+    subject { cluster.group }
+
+    context 'when cluster belongs to a group' do
+      let(:cluster) { create(:cluster, :group) }
+      let(:group) { cluster.groups.first }
+
+      it { is_expected.to eq(group) }
+    end
+
+    context 'when cluster does not belong to any group' do
+      let(:cluster) { create(:cluster) }
+
+      it { is_expected.to be_nil }
+    end
+  end
+
   describe '#applications' do
     set(:cluster) { create(:cluster) }
 

spec/models/clusters/group_spec.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Clusters::Group do
+  it { is_expected.to belong_to(:cluster) }
+  it { is_expected.to belong_to(:group) }
+end

spec/models/group_spec.rb

@@ -19,6 +19,8 @@ describe Group do
     it { is_expected.to have_one(:chat_team) }
     it { is_expected.to have_many(:custom_attributes).class_name('GroupCustomAttribute') }
     it { is_expected.to have_many(:badges).class_name('GroupBadge') }
+    it { is_expected.to have_many(:cluster_groups).class_name('Clusters::Group') }
+    it { is_expected.to have_many(:clusters).class_name('Clusters::Cluster') }
 
     describe '#members & #requesters' do
       let(:requester) { create(:user) }