diff --git a/config.ru b/config.ru
index 1b244c3..99d80d8 100644
--- a/config.ru
+++ b/config.ru
@@ -1,7 +1,6 @@
 # vim: set noet sw=2 ts=2 sts=2:
 require 'rack'
 require_relative 'dnsbl_exporter'
-require 'yaml'
 
 DnsblCollector.load_config './config.yml'
 
@@ -26,7 +25,7 @@ run lambda {|env|
       [404, {"Content-Type" => "text/plain"}, ["Not found.\nYou want to try /metrics?\n"]]
     end
   rescue
-    STDERR.puts "#$! (#{$!.class})", $!.backtrace
+    STDERR.puts "#$! (#{$!.class})", *$!.backtrace
     [500, {"Content-Type" => "text/plain"}, ["Server-error.\n"]]
   end
 }
diff --git a/dnsbl_exporter.rb b/dnsbl_exporter.rb
index c0d60ad..23532da 100644
--- a/dnsbl_exporter.rb
+++ b/dnsbl_exporter.rb
@@ -43,8 +43,11 @@ class DnsblCollector
 		end
 	end
 
+	# The general Registry for the process.
+	# It stores not request-related metrices.
 	self.registry = Prometheus::Client::Registry.new
 
+	# @registry stores only request-related metrices.
 	attr_reader :lists, :registry, :configfile, :resolver, :metrics
 
 	def initialize registry: nil