2 files changed, 57 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/test_fixtures.rb b/activerecord/lib/active_record/test_fixtures.rb
index 7b7b3f7112..d29fc9f84b 100644
--- a/activerecord/lib/active_record/test_fixtures.rb
+++ b/activerecord/lib/active_record/test_fixtures.rb
@@ -173,10 +173,33 @@ module ActiveRecord
     end
 
     def enlist_fixture_connections
+      setup_shared_connection_pool
+
       ActiveRecord::Base.connection_handler.connection_pool_list.map(&:connection)
     end
 
     private
+
+      # Shares the writing connection pool with connections on
+      # other handlers.
+      #
+      # In an application with a primary and replica the test fixtures
+      # need to share a connection pool so that the reading connection
+      # can see data in the open transaction on the writing connection.
+      def setup_shared_connection_pool
+        writing_handler = ActiveRecord::Base.connection_handler
+
+        ActiveRecord::Base.connection_handlers.values.each do |handler|
+          if handler != writing_handler
+            handler.connection_pool_list.each do |pool|
+              name = pool.spec.name
+              writing_connection = writing_handler.retrieve_connection_pool(name)
+              handler.send(:owner_to_pool)[name] = writing_connection
+            end
+          end
+        end
+      end
+
       def load_fixtures(config)
         fixtures = ActiveRecord::FixtureSet.create_fixtures(fixture_path, fixture_table_names, fixture_class_names, config)
         Hash[fixtures.map { |f| [f.name, f] }]
diff --git a/activerecord/test/cases/fixtures_test.rb b/activerecord/test/cases/fixtures_test.rb
index fe2f417a04..32021c5ebd 100644
--- a/activerecord/test/cases/fixtures_test.rb
+++ b/activerecord/test/cases/fixtures_test.rb
@@ -1362,3 +1362,37 @@ class NilFixturePathTest < ActiveRecord::TestCase
     MSG
   end
 end
+
+class MultipleDatabaseFixturesTest < ActiveRecord::TestCase
+  test "enlist_fixture_connections ensures multiple databases share a connection pool" do
+    with_temporary_connection_pool do
+      ActiveRecord::Base.connects_to database: { writing: :arunit, reading: :arunit2 }
+
+      rw_conn = ActiveRecord::Base.connection
+      ro_conn = ActiveRecord::Base.connection_handlers[:reading].connection_pool_list.first.connection
+
+      assert_not_equal rw_conn, ro_conn
+
+      enlist_fixture_connections
+
+      rw_conn = ActiveRecord::Base.connection
+      ro_conn = ActiveRecord::Base.connection_handlers[:reading].connection_pool_list.first.connection
+
+      assert_equal rw_conn, ro_conn
+    end
+  ensure
+    ActiveRecord::Base.connection_handlers = { writing: ActiveRecord::Base.connection_handler }
+  end
+
+  private
+
+    def with_temporary_connection_pool
+      old_pool = ActiveRecord::Base.connection_handler.retrieve_connection_pool(ActiveRecord::Base.connection_specification_name)
+      new_pool = ActiveRecord::ConnectionAdapters::ConnectionPool.new ActiveRecord::Base.connection_pool.spec
+      ActiveRecord::Base.connection_handler.send(:owner_to_pool)["primary"] = new_pool
+
+      yield
+    ensure
+      ActiveRecord::Base.connection_handler.send(:owner_to_pool)["primary"] = old_pool
+    end
+end