conf.keys.select { |key| key =~ /^filter\d+$/ }.sort_by { |key| key.sub('filter', '').to_i }.each do |key|
      begin
        @filters << instance_eval("lambda do |tag, time, record| #{conf[key]} end")
      rescue Exception => e
        raise Fluent::ConfigError, "#{key} #{conf[key]}\n" + e.to_s