Utility for detecting cross DB data modification

lib/gitlab/database.rb

@@ -147,6 +147,11 @@ module Gitlab
       # spec/support/database/prevent_cross_joins.rb
     end
 
+    def self.allow_cross_database_modification_within_transaction(url:)
+      # this method is implemented in:
+      # spec/support/database/cross_database_modification_check.rb
+    end
+
     def self.add_post_migrate_path_to_rails(force: false)
       return if ENV['SKIP_POST_DEPLOYMENT_MIGRATIONS'] && !force
 

spec/support/database/ci_tables.rb

+# frozen_string_literal: true
+
+# This module stores the CI-related database tables which are
+# going to be moved to a separate database.
+module Database
+  module CiTables
+    def self.include?(name)
+      ci_tables.include?(name)
+    end
+
+    def self.ci_tables
+      @@ci_tables ||= Set.new.tap do |tables| # rubocop:disable Style/ClassVars
+        tables.merge(Ci::ApplicationRecord.descendants.map(&:table_name).compact)
+
+        # It was decided that taggings/tags are best placed with CI
+        # https://gitlab.com/gitlab-org/gitlab/-/issues/333413
+        tables.add('taggings')
+        tables.add('tags')
+      end
+    end
+  end
+end

spec/support/database/prevent_cross_database_modification.rb

+# frozen_string_literal: true
+
+module Database
+  module PreventCrossDatabaseModification
+    CrossDatabaseModificationAcrossUnsupportedTablesError = Class.new(StandardError)
+
+    module GitlabDatabaseMixin
+      def allow_cross_database_modification_within_transaction(url:)
+        return yield unless Thread.current[:transaction_tracker]
+
+        cross_database_context = Database::PreventCrossDatabaseModification.cross_database_context
+        return yield unless cross_database_context[:enabled]
+
+        transaction_tracker_enabled_was = cross_database_context[:enabled]
+        cross_database_context[:enabled] = false
+
+        yield
+      ensure
+        cross_database_context[:enabled] = transaction_tracker_enabled_was if Thread.current[:transaction_tracker]
+      end
+    end
+
+    module SpecHelpers
+      def with_cross_database_modification_prevented
+        subscriber = ActiveSupport::Notifications.subscribe('sql.active_record') do |name, start, finish, id, payload|
+          PreventCrossDatabaseModification.prevent_cross_database_modification!(payload[:connection], payload[:sql])
+        end
+
+        PreventCrossDatabaseModification.reset_cross_database_context!
+        PreventCrossDatabaseModification.cross_database_context.merge!(enabled: true, subscriber: subscriber)
+
+        yield if block_given?
+      ensure
+        cleanup_with_cross_database_modification_prevented if block_given?
+      end
+
+      def cleanup_with_cross_database_modification_prevented
+        ActiveSupport::Notifications.unsubscribe(PreventCrossDatabaseModification.cross_database_context[:subscriber])
+        PreventCrossDatabaseModification.cross_database_context[:enabled] = false
+      end
+    end
+
+    def self.cross_database_context
+      Thread.current[:transaction_tracker] ||= initial_data
+    end
+
+    def self.reset_cross_database_context!
+      Thread.current[:transaction_tracker] = initial_data
+    end
+
+    def self.initial_data
+      {
+        enabled: false,
+        transaction_depth_by_db: Hash.new { |h, k| h[k] = 0 },
+        modified_tables_by_db: Hash.new { |h, k| h[k] = Set.new }
+      }
+    end
+
+    def self.prevent_cross_database_modification!(connection, sql)
+      return unless cross_database_context[:enabled]
+
+      database = connection.pool.db_config.name
+
+      if sql.start_with?('SAVEPOINT')
+        cross_database_context[:transaction_depth_by_db][database] += 1
+
+        return
+      elsif sql.start_with?('RELEASE SAVEPOINT', 'ROLLBACK TO SAVEPOINT')
+        cross_database_context[:transaction_depth_by_db][database] -= 1
+        if cross_database_context[:transaction_depth_by_db][database] <= 0
+          cross_database_context[:modified_tables_by_db][database].clear
+        end
+
+        return
+      end
+
+      return if cross_database_context[:transaction_depth_by_db].values.all?(&:zero?)
+
+      tables = PgQuery.parse(sql).dml_tables
+
+      return if tables.empty?
+
+      cross_database_context[:modified_tables_by_db][database].merge(tables)
+
+      ci_table_referenced = false
+      main_table_referenced = false
+      all_tables = cross_database_context[:modified_tables_by_db].values.map(&:to_a).flatten
+      all_tables.each do |table|
+        if Database::CiTables.include?(table)
+          ci_table_referenced = true
+        else
+          main_table_referenced = true
+        end
+      end
+
+      if ci_table_referenced && main_table_referenced
+        raise Database::PreventCrossDatabaseModification::CrossDatabaseModificationAcrossUnsupportedTablesError,
+          "Cross-database data modification queries (CI and Main) were detected within " \
+          "a transaction '#{all_tables.join(", ")}' discovered"
+      end
+    end
+  end
+end
+
+Gitlab::Database.singleton_class.prepend(
+  Database::PreventCrossDatabaseModification::GitlabDatabaseMixin)
+
+RSpec.configure do |config|
+  config.include(::Database::PreventCrossDatabaseModification::SpecHelpers)
+
+  # Using before and after blocks because the around block causes problems with the let_it_be
+  # record creations. It makes an extra savepoint which breaks the transaction count logic.
+  config.before(:each, :prevent_cross_database_modification) do
+    with_cross_database_modification_prevented
+  end
+
+  config.after(:each, :prevent_cross_database_modification) do
+    cleanup_with_cross_database_modification_prevented
+  end
+end

spec/support/database/prevent_cross_joins.rb

@@ -37,23 +37,8 @@ module Database
 
     # Returns true if a set includes only CI tables, or includes only non-CI tables
     def self.only_ci_or_only_main?(tables)
-      tables.all? { |table| ci_table_name?(table) } ||
-        tables.none? { |table| ci_table_name?(table) }
-    end
-
-    def self.ci_table_name?(name)
-      ci_tables.include?(name)
-    end
-
-    def self.ci_tables
-      @@ci_tables ||= Set.new.tap do |tables| # rubocop:disable Style/ClassVars
-        tables.merge(Ci::ApplicationRecord.descendants.map(&:table_name).compact)
-
-        # It was decided that taggings/tags are best placed with CI
-        # https://gitlab.com/gitlab-org/gitlab/-/issues/333413
-        tables.add('taggings')
-        tables.add('tags')
-      end
+      tables.all? { |table| CiTables.include?(table) } ||
+        tables.none? { |table| CiTables.include?(table) }
     end
 
     module SpecHelpers

spec/support_specs/database/prevent_cross_database_modification_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Database::PreventCrossDatabaseModification' do
+  let_it_be(:pipeline, refind: true) { create(:ci_pipeline) }
+  let_it_be(:project, refind: true) { create(:project) }
+
+  shared_examples 'succeessful examples' do
+    context 'outside transaction' do
+      it { expect { run_queries }.not_to raise_error }
+    end
+
+    context 'within transaction' do
+      it do
+        Project.transaction do
+          expect { run_queries }.not_to raise_error
+        end
+      end
+    end
+
+    context 'within nested transaction' do
+      it do
+        Project.transaction(requires_new: true) do
+          Project.transaction(requires_new: true) do
+            expect { run_queries }.not_to raise_error
+          end
+        end
+      end
+    end
+  end
+
+  context 'when CI and other tables are read in a transaction' do
+    def run_queries
+      pipeline.reload
+      project.reload
+    end
+
+    include_examples 'succeessful examples'
+  end
+
+  context 'when only CI data is modified' do
+    def run_queries
+      pipeline.touch
+      project.reload
+    end
+
+    include_examples 'succeessful examples'
+  end
+
+  context 'when other data is modified' do
+    def run_queries
+      pipeline.reload
+      project.touch
+    end
+
+    include_examples 'succeessful examples'
+  end
+
+  describe 'with_cross_database_modification_prevented block' do
+    it 'raises error when CI and other data is modified' do
+      expect do
+        with_cross_database_modification_prevented do
+          Project.transaction do
+            project.touch
+            pipeline.touch
+          end
+        end
+      end.to raise_error /Cross-database data modification queries/
+    end
+  end
+
+  context 'when running tests with prevent_cross_database_modification', :prevent_cross_database_modification do
+    context 'when both CI and other data is modified' do
+      def run_queries
+        project.touch
+        pipeline.touch
+      end
+
+      context 'outside transaction' do
+        it { expect { run_queries }.not_to raise_error }
+      end
+
+      context 'when data modification happens in a transaction' do
+        it 'raises error' do
+          Project.transaction do
+            expect { run_queries }.to raise_error /Cross-database data modification queries/
+          end
+        end
+
+        context 'when data modification happens in nested transactions' do
+          it 'raises error' do
+            Project.transaction(requires_new: true) do
+              project.touch
+              Project.transaction(requires_new: true) do
+                expect { pipeline.touch }.to raise_error /Cross-database data modification queries/
+              end
+            end
+          end
+        end
+      end
+    end
+
+    context 'when CI association is modified through project' do
+      def run_queries
+        project.variables.build(key: 'a', value: 'v')
+        project.save!
+      end
+
+      include_examples 'succeessful examples'
+    end
+
+    describe '#allow_cross_database_modification_within_transaction' do
+      it 'skips raising error' do
+        expect do
+          Gitlab::Database.allow_cross_database_modification_within_transaction(url: 'gitlab-issue') do
+            Project.transaction do
+              pipeline.touch
+              project.touch
+            end
+          end
+        end.not_to raise_error
+      end
+
+      it 'raises error when complex factories are built referencing both databases' do
+        expect do
+          ApplicationRecord.transaction do
+            create(:ci_pipeline)
+          end
+        end.to raise_error /Cross-database data modification queries/
+      end
+
+      it 'skips raising error on factory creation' do
+        expect do
+          Gitlab::Database.allow_cross_database_modification_within_transaction(url: 'gitlab-issue') do
+            ApplicationRecord.transaction do
+              create(:ci_pipeline)
+            end
+          end
+        end.not_to raise_error
+      end
+    end
+  end
+end