def search_driver_connection_pool(driver_class, driver_config)
      if RailsKvsDriver::KVS_CONNECTION_POOL.has_key?(driver_class.name)
        RailsKvsDriver::KVS_CONNECTION_POOL[driver_class.name].each do |pool_set|
          return pool_set[:pool] if equal_driver_config?(pool_set[:config], driver_config)
        end
      end

      return nil
    end
def search_driver_connection_pool(driver_class, driver_config)
      if RailsKvsDriver::KVS_CONNECTION_POOL.has_key?(driver_class.name)
        RailsKvsDriver::KVS_CONNECTION_POOL[driver_class.name].each do |pool_set|
          return pool_set[:pool] if equal_driver_config?(pool_set[:config], driver_config)
        end
      end

      return nil
    end
search driver connection pool

 @param driver_class   [RailsKvsDriver::Base]  driver_class
 @param driver_config  [Hash]                  driver_config
 @return [ConnectionPool] connection pool of driver, or nil