config/initializers/sequel_init.rb

sequel_init.rb

require ‘sequel’

module MyApp
  class SequelDb
    class << self
      attr_reader :main_db, :alt_db

      def start_connections
        @main_db ||= establish_connection
        @alt_db  ||= establish_connection('alternative-database-name')
      end
      
      def disconnect_all
        main_db.disconnect
        alt_db.disconnect
      end
      
      private

      def establish_connection(database = nil)
        Sequel.connect(params_to_connect(database))
      end

      def params_to_connect(database = nil)
        options = db_config
        options.merge!(database: database) if database
        options
      end

      def db_config
        YAML.load_file(File.expand_path('../../database.yml', __FILE__))[Rails.env]
      end
    end
  end
end

MyApp::SequelDb.start_connections