From 31021a8c85bb80300deb01db96876858ff417f4a Mon Sep 17 00:00:00 2001 From: Eileen Uchitelle Date: Fri, 28 Sep 2018 16:52:54 -0400 Subject: Basic API for connection switching This PR adds the ability to 1) connect to multiple databases in a model, and 2) switch between those connections using a block. To connect a model to a set of databases for writing and reading use the following API. This API supercedes `establish_connection`. The `writing` and `reading` keys represent handler / role names and `animals` and `animals_replica` represents the database key to look up the configuration hash from. ``` class AnimalsBase < ApplicationRecord connects_to database: { writing: :animals, reading: :animals_replica } end ``` Inside the application - outside the model declaration - we can switch connections with a block call to `connected_to`. If we want to connect to a db that isn't default (ie readonly_slow) we can connect like this: Outside the model we may want to connect to a new database (one that is not in the default writing/reading set) - for example a slow replica for making slow queries. To do this we have the `connected_to` method that takes a `database` hash that matches the signature of `connects_to`. The `connected_to` method also takes a block. ``` AcitveRecord::Base.connected_to(database: { slow_readonly: :primary_replica_slow }) do ModelInPrimary.do_something_thats_slow end ``` For models that are already loaded and connections that are already connected, `connected_to` doesn't need to pass in a `database` because you may want to run queries against multiple databases using a specific role/handler. In this case `connected_to` can take a `role` and use that to swap on the connection passed. This simplies queries - and matches how we do it in GitHub. Once you're connected to the database you don't need to re-connect, we assume the connection is in the pool and simply pass the handler we'd like to swap on. ``` ActiveRecord::Base.connected_to(role: :reading) do Dog.read_something_from_dog ModelInPrimary.do_something_from_model_in_primary end ``` --- .../connection_handlers_multi_db_test.rb | 193 +++++++++++++++++++++ 1 file changed, 193 insertions(+) create mode 100644 activerecord/test/cases/connection_adapters/connection_handlers_multi_db_test.rb (limited to 'activerecord/test/cases/connection_adapters') diff --git a/activerecord/test/cases/connection_adapters/connection_handlers_multi_db_test.rb b/activerecord/test/cases/connection_adapters/connection_handlers_multi_db_test.rb new file mode 100644 index 0000000000..d4e8cbee81 --- /dev/null +++ b/activerecord/test/cases/connection_adapters/connection_handlers_multi_db_test.rb @@ -0,0 +1,193 @@ +# frozen_string_literal: true + +require "cases/helper" +require "models/person" + +module ActiveRecord + module ConnectionAdapters + class ConnectionHandlersMultiDbTest < ActiveRecord::TestCase + self.use_transactional_tests = false + + fixtures :people + + def setup + @handlers = { writing: ConnectionHandler.new, reading: ConnectionHandler.new } + @rw_handler = @handlers[:writing] + @ro_handler = @handlers[:reading] + @spec_name = "primary" + @rw_pool = @handlers[:writing].establish_connection(ActiveRecord::Base.configurations["arunit"]) + @ro_pool = @handlers[:reading].establish_connection(ActiveRecord::Base.configurations["arunit"]) + end + + def teardown + ActiveRecord::Base.connection_handlers = { writing: ActiveRecord::Base.default_connection_handler } + end + + class MultiConnectionTestModel < ActiveRecord::Base + end + + def test_multiple_connection_handlers_works_in_a_threaded_environment + tf_writing = Tempfile.open "test_writing" + tf_reading = Tempfile.open "test_reading" + + MultiConnectionTestModel.connects_to database: { writing: { database: tf_writing.path, adapter: "sqlite3" }, reading: { database: tf_reading.path, adapter: "sqlite3" } } + + MultiConnectionTestModel.connection.execute("CREATE TABLE `test_1` (connection_role VARCHAR (255))") + MultiConnectionTestModel.connection.execute("INSERT INTO test_1 VALUES ('writing')") + + ActiveRecord::Base.connected_to(role: :reading) do + MultiConnectionTestModel.connection.execute("CREATE TABLE `test_1` (connection_role VARCHAR (255))") + MultiConnectionTestModel.connection.execute("INSERT INTO test_1 VALUES ('reading')") + end + + read_latch = Concurrent::CountDownLatch.new + write_latch = Concurrent::CountDownLatch.new + + MultiConnectionTestModel.connection + + thread = Thread.new do + MultiConnectionTestModel.connection + + write_latch.wait + assert_equal "writing", MultiConnectionTestModel.connection.select_value("SELECT connection_role from test_1") + read_latch.count_down + end + + ActiveRecord::Base.connected_to(role: :reading) do + write_latch.count_down + assert_equal "reading", MultiConnectionTestModel.connection.select_value("SELECT connection_role from test_1") + read_latch.wait + end + + thread.join + ensure + tf_reading.close + tf_reading.unlink + tf_writing.close + tf_writing.unlink + end + + unless in_memory_db? + def test_establish_connection_using_3_levels_config + previous_env, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], "default_env" + + config = { + "default_env" => { + "readonly" => { "adapter" => "sqlite3", "database" => "db/readonly.sqlite3" }, + "primary" => { "adapter" => "sqlite3", "database" => "db/primary.sqlite3" } + } + } + @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config + + ActiveRecord::Base.connects_to(database: { writing: :primary, reading: :readonly }) + + assert_not_nil pool = ActiveRecord::Base.connection_handlers[:writing].retrieve_connection_pool("primary") + assert_equal "db/primary.sqlite3", pool.spec.config[:database] + + assert_not_nil pool = ActiveRecord::Base.connection_handlers[:reading].retrieve_connection_pool("primary") + assert_equal "db/readonly.sqlite3", pool.spec.config[:database] + ensure + ActiveRecord::Base.configurations = @prev_configs + ActiveRecord::Base.establish_connection(:arunit) + ENV["RAILS_ENV"] = previous_env + end + + def test_switching_connections_via_handler + previous_env, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], "default_env" + + config = { + "default_env" => { + "readonly" => { "adapter" => "sqlite3", "database" => "db/readonly.sqlite3" }, + "primary" => { "adapter" => "sqlite3", "database" => "db/primary.sqlite3" } + } + } + @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config + + ActiveRecord::Base.connects_to(database: { writing: :primary, reading: :readonly }) + + ActiveRecord::Base.connected_to(role: :reading) do + @ro_handler = ActiveRecord::Base.connection_handler + assert_equal ActiveRecord::Base.connection_handler, ActiveRecord::Base.connection_handlers[:reading] + end + + ActiveRecord::Base.connected_to(role: :writing) do + assert_equal ActiveRecord::Base.connection_handler, ActiveRecord::Base.connection_handlers[:writing] + assert_not_equal @ro_handler, ActiveRecord::Base.connection_handler + end + ensure + ActiveRecord::Base.configurations = @prev_configs + ActiveRecord::Base.establish_connection(:arunit) + ENV["RAILS_ENV"] = previous_env + end + + def test_connects_to_with_single_configuration + config = { + "development" => { "adapter" => "sqlite3", "database" => "db/primary.sqlite3" }, + } + @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config + + ActiveRecord::Base.connects_to database: { writing: :development } + + assert_equal 1, ActiveRecord::Base.connection_handlers.size + assert_equal ActiveRecord::Base.connection_handler, ActiveRecord::Base.connection_handlers[:writing] + ensure + ActiveRecord::Base.configurations = @prev_configs + ActiveRecord::Base.establish_connection(:arunit) + end + + def test_connects_to_using_top_level_key_in_two_level_config + config = { + "development" => { "adapter" => "sqlite3", "database" => "db/primary.sqlite3" }, + "development_readonly" => { "adapter" => "sqlite3", "database" => "db/readonly.sqlite3" } + } + @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config + + ActiveRecord::Base.connects_to database: { writing: :development, reading: :development_readonly } + + assert_not_nil pool = ActiveRecord::Base.connection_handlers[:reading].retrieve_connection_pool("primary") + assert_equal "db/readonly.sqlite3", pool.spec.config[:database] + ensure + ActiveRecord::Base.configurations = @prev_configs + ActiveRecord::Base.establish_connection(:arunit) + end + end + + def test_connection_pools + assert_equal([@rw_pool], @handlers[:writing].connection_pools) + assert_equal([@ro_pool], @handlers[:reading].connection_pools) + end + + def test_retrieve_connection + assert @rw_handler.retrieve_connection(@spec_name) + assert @ro_handler.retrieve_connection(@spec_name) + end + + def test_active_connections? + assert_not_predicate @rw_handler, :active_connections? + assert_not_predicate @ro_handler, :active_connections? + + assert @rw_handler.retrieve_connection(@spec_name) + assert @ro_handler.retrieve_connection(@spec_name) + + assert_predicate @rw_handler, :active_connections? + assert_predicate @ro_handler, :active_connections? + + @rw_handler.clear_active_connections! + assert_not_predicate @rw_handler, :active_connections? + + @ro_handler.clear_active_connections! + assert_not_predicate @ro_handler, :active_connections? + end + + def test_retrieve_connection_pool + assert_not_nil @rw_handler.retrieve_connection_pool(@spec_name) + assert_not_nil @ro_handler.retrieve_connection_pool(@spec_name) + end + + def test_retrieve_connection_pool_with_invalid_id + assert_nil @rw_handler.retrieve_connection_pool("foo") + assert_nil @ro_handler.retrieve_connection_pool("foo") + end + end + end +end -- cgit v1.2.3