Make this gem work with mysql2 and trilogy

Notes:

- Trilogy does not like integers as DB passwords so we must now pass string literals as the password(s) in our database ymls.
- `mysql2` has a `select_db` method but the equivalent method in `trilogy` is `change_db`
- `Trilogy` will raise an `ActiveRecord::StatementInvalid` error when attempting to use an invalid connection

Co-authored-by: Benjamin Quorning <bquorning@zendesk.com>

Co-authored-by: Benjamin Quorning <bquorning@zendesk.com>

Changelog.md

@@ -6,6 +6,7 @@ and as of v1.0.0 this project adheres to [Semantic Versioning](https://semver.or
 
 ## [Unreleased]
 
+- Remove `mysql2` as a direct dependency, test Rails 7.0 with `mysql2` and `activerecord-trilogy-adapter`
 - Drop Ruby 2.6.
 - Start testing with Ruby 3.2.
 

Readme.md

@@ -43,7 +43,7 @@ test_pool_2 => 127.0.0.1/3306//root/false
 
 ## Support
 
-For now, the only backend known to work is MySQL, with the mysql2 gem.
+For now, the only backend known to work is MySQL, with the mysql2 or activerecord-trilogy-adapter gem.
 Postgres, from an informal reading of the docs, will never support the concept of one server connection sharing multiple dbs.
 
 ## Installation

lib/active_record_host_pool.rb

@@ -1,5 +1,19 @@
 # frozen_string_literal: true
 
+module ActiveRecordHostPool
+  class << self
+    attr_accessor :loaded_db_adapter
+  end
+end
+
+begin
+  require 'mysql2'
+  ActiveRecordHostPool.loaded_db_adapter = :mysql2
+rescue LoadError
+  require 'activerecord-trilogy-adapter'
+  ActiveRecordHostPool.loaded_db_adapter = :trilogy
+end
+
 require 'active_record'
 require 'active_record/base'
 require 'active_record/connection_adapters/abstract_adapter'
@@ -9,6 +23,3 @@
 require 'active_record_host_pool/pool_proxy'
 require 'active_record_host_pool/connection_adapter_mixin'
 require 'active_record_host_pool/version'
-
-module ActiveRecordHostPool
-end

lib/active_record_host_pool/connection_adapter_mixin.rb

@@ -1,6 +1,13 @@
 # frozen_string_literal: true
 
-require "active_record/connection_adapters/mysql2_adapter"
+case ActiveRecordHostPool.loaded_db_adapter
+when :mysql2
+  require "active_record/connection_adapters/mysql2_adapter"
+when :trilogy
+  require 'trilogy_adapter/connection'
+  require "trilogy_adapter/errors"
+  ActiveRecord::Base.extend TrilogyAdapter::Connection
+end
 
 module ActiveRecordHostPool
   module DatabaseSwitch
@@ -75,13 +82,24 @@ def _switch_connection
          )
         log("select_db #{_host_pool_current_database}", "SQL") do
           clear_cache! if respond_to?(:clear_cache!)
-          raw_connection.select_db(_host_pool_current_database)
+          _arhp_select_db(_host_pool_current_database)
         end
         @_cached_current_database = _host_pool_current_database
         @_cached_connection_object_id = @connection.object_id
       end
     end
 
+    case ActiveRecordHostPool.loaded_db_adapter
+    when :mysql2
+      def _arhp_select_db(database)
+        raw_connection.select_db(database)
+      end
+    when :trilogy
+      def _arhp_select_db(database) # rubocop:disable Lint/DuplicateMethods
+        raw_connection.change_db(database)
+      end
+    end
+
     # prevent different databases from sharing the same query cache
     def cache_sql(sql, *args)
       super(_host_pool_current_database.to_s + "/" + sql, *args)
@@ -122,7 +140,12 @@ def establish_connection(spec)
   end
 end
 
-ActiveRecord::ConnectionAdapters::Mysql2Adapter.include(ActiveRecordHostPool::DatabaseSwitch)
+case ActiveRecordHostPool.loaded_db_adapter
+when :mysql2
+  ActiveRecord::ConnectionAdapters::Mysql2Adapter.include(ActiveRecordHostPool::DatabaseSwitch)
+when :trilogy
+  ActiveRecord::ConnectionAdapters::TrilogyAdapter.include(ActiveRecordHostPool::DatabaseSwitch)
+end
 
 # In Rails 6.1 Connection Pools are no longer instantiated in #establish_connection but in a
 # new pool method.

lib/active_record_host_pool/pool_proxy_6_1.rb

@@ -15,6 +15,13 @@
 module ActiveRecordHostPool
   # Sits between ConnectionHandler and a bunch of different ConnectionPools (one per host).
   class PoolProxy < Delegator
+    case ActiveRecordHostPool.loaded_db_adapter
+    when :mysql2
+      RESCUABLE_DB_ERROR = Mysql2::Error
+    when :trilogy
+      RESCUABLE_DB_ERROR = Trilogy::ProtocolError
+    end
+
     def initialize(pool_config)
       super(pool_config)
       @pool_config = pool_config
@@ -36,7 +43,7 @@ def __setobj__(pool_config)
     def connection(*args)
       real_connection = _unproxied_connection(*args)
       _connection_proxy_for(real_connection, @config[:database])
-    rescue Mysql2::Error, ActiveRecord::NoDatabaseError
+    rescue RESCUABLE_DB_ERROR, ActiveRecord::NoDatabaseError, ActiveRecord::StatementInvalid
       _connection_pools.delete(_pool_key)
       Kernel.raise
     end

test/database.yml

@@ -1,4 +1,6 @@
 <% mysql = URI(ENV['MYSQL_URL'] || 'mysql://root@127.0.0.1:3306') %>
+<% adapter = ActiveRecordHostPool.loaded_db_adapter %>
+
 # ARHP creates separate connection pools based on the pool key.
 # The pool key is defined as:
 #   host / port / socket / username / replica
@@ -28,65 +30,65 @@
 #       test_pool_2 => 127.0.0.1/3306//root/false
 
 test_pool_1_db_a:
-  adapter: mysql2
+  adapter: <%= adapter %>
   encoding: utf8
   database: arhp_test_db_a
   username: <%= mysql.user %>
-  password: <%= mysql.password %>
+  password: "<%= mysql.password %>"
   host: <%= mysql.host %>
   reconnect: true
 
 # Mimic configurations as read by active_record_shards/ar_flexmaster
 test_pool_1_db_a_replica:
-  adapter: mysql2
+  adapter: <%= adapter %>
   encoding: utf8
   database: arhp_test_db_a_replica
   username: <%= mysql.user %>
-  password: <%= mysql.password %>
+  password: "<%= mysql.password %>"
   host: <%= mysql.host %>
   reconnect: true
   slave: true
 
 test_pool_1_db_b:
-  adapter: mysql2
+  adapter: <%= adapter %>
   encoding: utf8
   database: arhp_test_db_b
   username: <%= mysql.user %>
-  password: <%= mysql.password %>
+  password: "<%= mysql.password %>"
   host: <%= mysql.host %>
   reconnect: true
 
 test_pool_1_db_not_there:
-  adapter: mysql2
+  adapter: <%= adapter %>
   encoding: utf8
   database: arhp_test_db_not_there
   username: <%= mysql.user %>
-  password: <%= mysql.password %>
+  password: "<%= mysql.password %>"
   host: <%= mysql.host %>
   reconnect: true
 
 test_pool_2_db_d:
-  adapter: mysql2
+  adapter: <%= adapter %>
   encoding: utf8
   database: arhp_test_db_d
   username: <%= mysql.user %>
-  password: <%= mysql.password %>
+  password: "<%= mysql.password %>"
   host: <%= mysql.host %>
   port: <%= mysql.port %>
   reconnect: true
 
 test_pool_2_db_e:
-  adapter: mysql2
+  adapter: <%= adapter %>
   encoding: utf8
   database: arhp_test_db_e
   username: <%= mysql.user %>
-  password: <%= mysql.password %>
+  password: "<%= mysql.password %>"
   host: <%= mysql.host %>
   port: <%= mysql.port %>
   reconnect: true
 
 test_pool_3_db_e:
-  adapter: mysql2
+  adapter: <%= adapter %>
   encoding: utf8
   database: arhp_test_db_e
   username: john-doe
@@ -99,10 +101,10 @@ test_pool_3_db_e:
 # otherwise the test_models_with_matching_hosts_and_non_matching_databases_issue_exists_without_arhp_patch
 # test fails
 test_pool_1_db_c:
-  adapter: mysql2
+  adapter: <%= adapter %>
   encoding: utf8
   database: arhp_test_db_c
   username: <%= mysql.user %>
-  password: <%= mysql.password %>
+  password: "<%= mysql.password %>"
   host: <%= mysql.host %>
   reconnect: true

test/test_arhp_caching.rb

@@ -63,7 +63,13 @@ def test_models_with_matching_hosts_and_non_matching_databases_issue_exists_with
         end
 
         cached_db = Pool1DbC.connection.unproxied.pool.connections.first.instance_variable_get(:@_cached_current_database)
-        assert_equal("Mysql2::Error: Table '#{cached_db}.pool1_db_cs' doesn't exist", exception.message)
+
+        case ActiveRecordHostPool.loaded_db_adapter
+        when :mysql2
+          assert_equal("Mysql2::Error: Table '#{cached_db}.pool1_db_cs' doesn't exist", exception.message)
+        when :trilogy
+          assert_equal("Trilogy::ProtocolError: 1146: Table '#{cached_db}.pool1_db_cs' doesn't exist", exception.message)
+        end
       end
     end
 

test/test_arhp_wrong_db.rb

@@ -10,10 +10,10 @@ def setup
     else
       Phenix.load_database_config
     end
-    ActiveRecordHostPool::PoolProxy.class_variable_set(:@@_connection_pools, {})
   end
 
   def teardown
+    ActiveRecordHostPool::PoolProxy.class_variable_set(:@@_connection_pools, {})
     Phenix.burn!
   end