Associate clusters model to groups34758-create-group-clusters

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.

3 files changed, 47 insertions, 1 deletions

diff --git a/db/migrate/20181014203236_create_cluster_groups.rb b/db/migrate/20181014203236_create_cluster_groups.rb
new file mode 100644
index 00000000000..69382d5c851
--- /dev/null
+++ b/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
diff --git a/db/migrate/20181017001059_add_cluster_type_to_clusters.rb b/db/migrate/20181017001059_add_cluster_type_to_clusters.rb
new file mode 100644
index 00000000000..191e7eb4fb3
--- /dev/null
+++ b/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
diff --git a/db/schema.rb b/db/schema.rb
index 7a75aafd7b0..a36399cb37e 100644
--- a/db/schema.rb
+++ b/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