def connection_pool
      return @connection_pool unless @connection_pool.nil?
      if self.beanstalk_addresses.nil?
        raise RuntimeError, 'beanstalk_addresses must be set in order to establish a connection'
      end
      @connection_pool = ConnectionPool.new(self.beanstalk_addresses, self.test_tube)
    end
def connection_pool
      return @connection_pool unless @connection_pool.nil?
      if self.beanstalk_addresses.nil?
        raise RuntimeError, 'beanstalk_addresses must be set in order to establish a connection'
      end
      @connection_pool = ConnectionPool.new(self.beanstalk_addresses, self.test_tube)
    end
:call-seq:
   connection_pool() => StalkClimber::ConnectionPool

 Returns or creates a ConnectionPool from beanstalk_addresses. Raises a
 RuntimeError if #beanstalk_addresses has not been set.