Add Geo::CacheInvalidationEvent model

These changes introduce a new Geo event that can be triggered
to invalidate the cache for a specific key on Geo secondaries.

This event is necessary because enabling/disabling features does
not propagate correctly to Geo secondaries. It could be used for
other caches in the future (or existing caches that we currently
set to very short expiration periods on the secondary).

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: 20180930171532) do
+ActiveRecord::Schema.define(version: 20181001172651) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -1076,6 +1076,10 @@ ActiveRecord::Schema.define(version: 20180930171532) do
 
   add_index "gcp_clusters", ["project_id"], name: "index_gcp_clusters_on_project_id", unique: true, using: :btree
 
+  create_table "geo_cache_invalidation_events", id: :bigserial, force: :cascade do |t|
+    t.string "key", null: false
+  end
+
   create_table "geo_event_log", id: :bigserial, force: :cascade do |t|
     t.datetime "created_at", null: false
     t.integer "repository_updated_event_id", limit: 8
@@ -1089,8 +1093,10 @@ ActiveRecord::Schema.define(version: 20180930171532) do
     t.integer "job_artifact_deleted_event_id", limit: 8
     t.integer "upload_deleted_event_id", limit: 8
     t.integer "reset_checksum_event_id", limit: 8
+    t.integer "cache_invalidation_event_id", limit: 8
   end
 
+  add_index "geo_event_log", ["cache_invalidation_event_id"], name: "index_geo_event_log_on_cache_invalidation_event_id", using: :btree
   add_index "geo_event_log", ["repositories_changed_event_id"], name: "index_geo_event_log_on_repositories_changed_event_id", using: :btree
   add_index "geo_event_log", ["repository_created_event_id"], name: "index_geo_event_log_on_repository_created_event_id", using: :btree
   add_index "geo_event_log", ["repository_deleted_event_id"], name: "index_geo_event_log_on_repository_deleted_event_id", using: :btree
@@ -3171,6 +3177,7 @@ ActiveRecord::Schema.define(version: 20180930171532) do
   add_foreign_key "gcp_clusters", "projects", on_delete: :cascade
   add_foreign_key "gcp_clusters", "services", on_delete: :nullify
   add_foreign_key "gcp_clusters", "users", on_delete: :nullify
+  add_foreign_key "geo_event_log", "geo_cache_invalidation_events", column: "cache_invalidation_event_id", name: "fk_42c3b54bed", on_delete: :cascade
   add_foreign_key "geo_event_log", "geo_hashed_storage_migrated_events", column: "hashed_storage_migrated_event_id", name: "fk_27548c6db3", on_delete: :cascade
   add_foreign_key "geo_event_log", "geo_job_artifact_deleted_events", column: "job_artifact_deleted_event_id", name: "fk_176d3fbb5d", on_delete: :cascade
   add_foreign_key "geo_event_log", "geo_lfs_object_deleted_events", column: "lfs_object_deleted_event_id", name: "fk_d5af95fcd9", on_delete: :cascade

ee/app/models/geo/cache_invalidation_event.rb

+# frozen_string_literal: true
+
+module Geo
+  class CacheInvalidationEvent < ActiveRecord::Base
+    include Geo::Model
+    include Geo::Eventable
+
+    validates :key, presence: true
+  end
+end

ee/app/models/geo/event_log.rb

@@ -3,7 +3,8 @@ module Geo
     include Geo::Model
     include ::EachBatch
 
-    EVENT_CLASSES = %w[Geo::RepositoryCreatedEvent
+    EVENT_CLASSES = %w[Geo::CacheInvalidationEvent
+                       Geo::RepositoryCreatedEvent
                        Geo::RepositoryUpdatedEvent
                        Geo::RepositoryDeletedEvent
                        Geo::RepositoryRenamedEvent
@@ -15,6 +16,10 @@ module Geo
                        Geo::JobArtifactDeletedEvent
                        Geo::UploadDeletedEvent].freeze
 
+    belongs_to :cache_invalidation_event,
+      class_name: 'Geo::CacheInvalidationEvent',
+      foreign_key: :cache_invalidation_event_id
+
     belongs_to :repository_created_event,
       class_name: 'Geo::RepositoryCreatedEvent',
       foreign_key: :repository_created_event_id
@@ -82,7 +87,8 @@ module Geo
         lfs_object_deleted_event ||
         job_artifact_deleted_event ||
         upload_deleted_event ||
-        reset_checksum_event
+        reset_checksum_event ||
+        cache_invalidation_event
     end
 
     def project_id

ee/db/migrate/20181001172126_create_geo_cache_invalidation_events.rb

+# frozen_string_literal: true
+
+class CreateGeoCacheInvalidationEvents < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def change
+    create_table :geo_cache_invalidation_events, id: :bigserial do |t|
+      t.string :key, null: false
+    end
+
+    add_column :geo_event_log, :cache_invalidation_event_id, :integer, limit: 8
+  end
+end

ee/db/migrate/20181001172651_add_geo_cache_invalidation_events_foreign_key.rb

+# frozen_string_literal: true
+
+class AddGeoCacheInvalidationEventsForeignKey < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_foreign_key :geo_event_log, :geo_cache_invalidation_events, column: :cache_invalidation_event_id, on_delete: :cascade
+    add_concurrent_index :geo_event_log, :cache_invalidation_event_id
+  end
+
+  def down
+    remove_foreign_key :geo_event_log, column: :cache_invalidation_event_id
+    remove_concurrent_index :geo_event_log, :cache_invalidation_event_id
+  end
+end

ee/spec/factories/geo/event_log.rb

@@ -39,6 +39,10 @@ FactoryBot.define do
     trait :reset_checksum_event do
       reset_checksum_event factory: :geo_reset_checksum_event
     end
+
+    trait :cache_invalidation_event do
+      cache_invalidation_event factory: :geo_cache_invalidation_event
+    end
   end
 
   factory :geo_repository_created_event, class: Geo::RepositoryCreatedEvent do
@@ -146,4 +150,8 @@ FactoryBot.define do
   factory :geo_reset_checksum_event, class: Geo::ResetChecksumEvent do
     project
   end
+
+  factory :geo_cache_invalidation_event, class: Geo::CacheInvalidationEvent do
+    sequence(:key) { |n| "cache-key-#{n}" }
+  end
 end

ee/spec/models/geo/cache_invalidation_event_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Geo::CacheInvalidationEvent, type: :model do
+  describe 'validations' do
+    it { is_expected.to validate_presence_of(:key) }
+  end
+end

ee/spec/models/geo/event_log_spec.rb

@@ -2,6 +2,7 @@ require 'spec_helper'
 
 RSpec.describe Geo::EventLog, type: :model do
   describe 'relationships' do
+    it { is_expected.to belong_to(:cache_invalidation_event).class_name('Geo::CacheInvalidationEvent').with_foreign_key('cache_invalidation_event_id') }
     it { is_expected.to belong_to(:repositories_changed_event).class_name('Geo::RepositoriesChangedEvent').with_foreign_key('repositories_changed_event_id') }
     it { is_expected.to belong_to(:repository_created_event).class_name('Geo::RepositoryCreatedEvent').with_foreign_key('repository_created_event_id') }
     it { is_expected.to belong_to(:repository_deleted_event).class_name('Geo::RepositoryDeletedEvent').with_foreign_key('repository_deleted_event_id') }
@@ -103,6 +104,13 @@ RSpec.describe Geo::EventLog, type: :model do
 
       expect(subject.event).to eq reset_checksum_event
     end
+
+    it 'returns cache_invalidation_event when set' do
+      cache_invalidation_event = build(:geo_cache_invalidation_event)
+      subject.cache_invalidation_event = cache_invalidation_event
+
+      expect(subject.event).to eq cache_invalidation_event
+    end
   end
 
   describe '#project_id' do