mysql2_em_sync_adapter.rb

require 'mysql2/em_fiber'
require 'active_record/connection_adapters/mysql2_adapter'

module ActiveRecord
  class Base
    def self.mysql2_em_sync_connection(config)
      config[:username] = 'root' if config[:username].nil?

      if Mysql2::Client.const_defined? :FOUND_ROWS
        config[:flags] = Mysql2::Client::FOUND_ROWS
      end

      client = Mysql2::EM::Fiber::Client.new(config.symbolize_keys)
      options = [config[:host], config[:username], config[:password], config[:database], config[:port], config[:socket], 0]
      ConnectionAdapters::Mysql2EMSyncAdapter.new(client, logger, options, config)
    end
  end

  module ConnectionAdapters
    class Mysql2EMSyncAdapter < Mysql2Adapter
      private
      def connect
        @connection = Mysql2::EM::Fiber::Client.new(@config)
        configure_connection
      end
    end

    class ConnectionPool
      private

      # we use fibers not threads. need a unique connection per fiber
      def current_connection_id
        Fiber.current.object_id
      end
    end
  end
end