Schedule 2nd migration of recalculating project authorizations

It adds a new background migration called
RecalculateProjectAuthorizationsWithMinMaxUserId along the already
existing RecalculateProjectAuthorizations to improve the performance of
the background migration.

changelogs/unreleased/security-recalculate_project_authorizations_run_2.yml

+---
+title: Recalculate ProjectAuthorizations for all users
+merge_request:
+author:
+type: security

db/post_migrate/20200204113224_schedule_recalculate_project_authorizations_second_run.rb

+# frozen_string_literal: true
+
+class ScheduleRecalculateProjectAuthorizationsSecondRun < ActiveRecord::Migration[5.1]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  MIGRATION = 'RecalculateProjectAuthorizationsWithMinMaxUserId'
+  BATCH_SIZE = 2_500
+  DELAY_INTERVAL = 2.minutes.to_i
+
+  disable_ddl_transaction!
+
+  class User < ActiveRecord::Base
+    include ::EachBatch
+
+    self.table_name = 'users'
+  end
+
+  def up
+    say "Scheduling #{MIGRATION} jobs"
+
+    User.each_batch(of: BATCH_SIZE) do |batch, index|
+      delay = index * DELAY_INTERVAL
+      range = batch.pluck('MIN(id)', 'MAX(id)').first
+      BackgroundMigrationWorker.perform_in(delay, MIGRATION, range)
+    end
+  end
+
+  def down
+  end
+end

lib/gitlab/background_migration/recalculate_project_authorizations_with_min_max_user_id.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # rubocop:disable Style/Documentation
+    class RecalculateProjectAuthorizationsWithMinMaxUserId
+      def perform(min_user_id, max_user_id)
+        User.where(id: min_user_id..max_user_id).find_each do |user|
+          service = Users::RefreshAuthorizedProjectsService.new(
+            user,
+            incorrect_auth_found_callback:
+              ->(project_id, access_level) do
+                logger.info(message: 'Removing ProjectAuthorizations',
+                            user_id: user.id,
+                            project_id: project_id,
+                            access_level: access_level)
+              end,
+            missing_auth_found_callback:
+              ->(project_id, access_level) do
+                logger.info(message: 'Creating ProjectAuthorizations',
+                            user_id: user.id,
+                            project_id: project_id,
+                            access_level: access_level)
+              end
+          )
+
+          service.execute
+        end
+      end
+
+      private
+
+      def logger
+        @logger ||= Gitlab::BackgroundMigration::Logger.build
+      end
+    end
+  end
+end

spec/lib/gitlab/background_migration/recalculate_project_authorizations_with_min_max_user_id_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::BackgroundMigration::RecalculateProjectAuthorizationsWithMinMaxUserId, :migration, schema: 20200204113224 do
+  let(:users_table) { table(:users) }
+  let(:min) { 1 }
+  let(:max) { 5 }
+
+  before do
+    min.upto(max) do |i|
+      users_table.create!(id: i, email: "user#{i}@example.com", projects_limit: 10)
+    end
+  end
+
+  describe '#perform' do
+    it 'initializes Users::RefreshAuthorizedProjectsService with correct users' do
+      min.upto(max) do |i|
+        user = User.find(i)
+        expect(Users::RefreshAuthorizedProjectsService).to(
+          receive(:new).with(user, any_args).and_call_original)
+      end
+
+      described_class.new.perform(min, max)
+    end
+
+    it 'executes Users::RefreshAuthorizedProjectsService' do
+      expected_call_counts = max - min + 1
+
+      service = instance_double(Users::RefreshAuthorizedProjectsService)
+      expect(Users::RefreshAuthorizedProjectsService).to(
+        receive(:new).exactly(expected_call_counts).times.and_return(service))
+      expect(service).to receive(:execute).exactly(expected_call_counts).times
+
+      described_class.new.perform(min, max)
+    end
+  end
+end

spec/migrations/schedule_recalculate_project_authorizations_second_run_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20200204113224_schedule_recalculate_project_authorizations_second_run.rb')
+
+describe ScheduleRecalculateProjectAuthorizationsSecondRun, :migration do
+  let(:users_table) { table(:users) }
+
+  before do
+    stub_const("#{described_class}::BATCH_SIZE", 2)
+
+    1.upto(4) do |i|
+      users_table.create!(id: i, name: "user#{i}", email: "user#{i}@example.com", projects_limit: 1)
+    end
+  end
+
+  it 'schedules background migration' do
+    Sidekiq::Testing.fake! do
+      Timecop.freeze do
+        migrate!
+
+        expect(BackgroundMigrationWorker.jobs.size).to eq(2)
+        expect(described_class::MIGRATION).to be_scheduled_migration(1, 2)
+        expect(described_class::MIGRATION).to be_scheduled_migration(3, 4)
+      end
+    end
+  end
+end