diff --git a/lib/fluent/agent.rb b/lib/fluent/agent.rb
index 1c766fe197..9543b4a277 100644
--- a/lib/fluent/agent.rb
+++ b/lib/fluent/agent.rb
@@ -13,10 +13,13 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 #
-module Fluent
-  require 'fluent/configurable'
-  require 'fluent/engine'
 
+require 'fluent/configurable'
+require 'fluent/engine'
+require 'fluent/plugin'
+require 'fluent/output'
+
+module Fluent
   #
   # Agent is a resource unit who manages emittable plugins
   #
diff --git a/lib/fluent/buffer.rb b/lib/fluent/buffer.rb
index 2187d835f1..d7327ddcbd 100644
--- a/lib/fluent/buffer.rb
+++ b/lib/fluent/buffer.rb
@@ -13,6 +13,12 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 #
+
+require 'monitor'
+require 'fileutils'
+
+require 'fluent/configurable'
+
 module Fluent
   class BufferError < StandardError
   end
diff --git a/lib/fluent/command/bundler_injection.rb b/lib/fluent/command/bundler_injection.rb
index 8e244f7ce5..5b90e0684b 100644
--- a/lib/fluent/command/bundler_injection.rb
+++ b/lib/fluent/command/bundler_injection.rb
@@ -14,6 +14,9 @@
 #    limitations under the License.
 #
 
+require 'rbconfig'
+require 'rubygems'
+
 if ENV['BUNDLE_BIN_PATH']
   puts 'error: You seem to use `bundle exec` already.'
   exit 1
diff --git a/lib/fluent/command/cat.rb b/lib/fluent/command/cat.rb
index 8ec8a5e2c1..172a066c86 100644
--- a/lib/fluent/command/cat.rb
+++ b/lib/fluent/command/cat.rb
@@ -66,7 +66,7 @@
   message_key = s
 }
 
-(class<<self;self;end).module_eval do
+(class << self; self; end).module_eval do
   define_method(:usage) do |msg|
     puts op.to_s
     puts "error: #{msg}" if msg
diff --git a/lib/fluent/command/debug.rb b/lib/fluent/command/debug.rb
index 22a21d18a5..1210695337 100644
--- a/lib/fluent/command/debug.rb
+++ b/lib/fluent/command/debug.rb
@@ -34,7 +34,7 @@
   unix = b
 }
 
-(class<<self;self;end).module_eval do
+(class << self; self; end).module_eval do
   define_method(:usage) do |msg|
     puts op.to_s
     puts "error: #{msg}" if msg
@@ -60,7 +60,8 @@
   uri = "druby://#{host}:#{port}"
 end
 
-require 'fluent/load'
+require 'fluent/log'
+require 'fluent/engine'
 
 $log = Fluent::Log.new(STDERR, Fluent::Log::LEVEL_TRACE)
 Fluent::Engine.init
diff --git a/lib/fluent/command/fluentd.rb b/lib/fluent/command/fluentd.rb
index 39fd24bc41..8e4a65c1e5 100644
--- a/lib/fluent/command/fluentd.rb
+++ b/lib/fluent/command/fluentd.rb
@@ -15,6 +15,7 @@
 #
 
 require 'optparse'
+
 require 'fluent/supervisor'
 
 op = OptionParser.new
@@ -119,7 +120,7 @@
   opts[:gem_install_path] = s
 }
 
-(class<<self;self;end).module_eval do
+(class << self; self; end).module_eval do
   define_method(:usage) do |msg|
     puts op.to_s
     puts "error: #{msg}" if msg
diff --git a/lib/fluent/config.rb b/lib/fluent/config.rb
index 5ff253a714..66cc47a69c 100644
--- a/lib/fluent/config.rb
+++ b/lib/fluent/config.rb
@@ -14,10 +14,11 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/config/error'
-  require 'fluent/config/element'
+require 'fluent/config/error'
+require 'fluent/config/element'
+require 'fluent/configurable'
 
+module Fluent
   module Config
     def self.parse(str, fname, basepath = Dir.pwd, v1_config = false)
       if fname =~ /\.rb$/
@@ -39,8 +40,6 @@ def self.new(name = '')
     end
   end
 
-  require 'fluent/configurable'
-
   module PluginId
     def configure(conf)
       @id = conf['@id'] || conf['id']
diff --git a/lib/fluent/config/basic_parser.rb b/lib/fluent/config/basic_parser.rb
index 7d695807fb..2a92f6b9b7 100644
--- a/lib/fluent/config/basic_parser.rb
+++ b/lib/fluent/config/basic_parser.rb
@@ -14,12 +14,11 @@
 #    limitations under the License.
 #
 
+require 'stringio'
+require 'fluent/config/error'
+
 module Fluent
   module Config
-
-    require 'stringio'
-    require 'fluent/config/error'
-
     class BasicParser
       def initialize(strscan)
         @ss = strscan
diff --git a/lib/fluent/config/configure_proxy.rb b/lib/fluent/config/configure_proxy.rb
index 5083da0b4a..af9be8d135 100644
--- a/lib/fluent/config/configure_proxy.rb
+++ b/lib/fluent/config/configure_proxy.rb
@@ -14,6 +14,8 @@
 #    limitations under the License.
 #
 
+require 'fluent/configurable'
+
 module Fluent
   module Config
     class ConfigureProxy
diff --git a/lib/fluent/config/dsl.rb b/lib/fluent/config/dsl.rb
index 8282007c48..538b13d5d6 100644
--- a/lib/fluent/config/dsl.rb
+++ b/lib/fluent/config/dsl.rb
@@ -14,7 +14,10 @@
 #    limitations under the License.
 #
 
+require 'json'
+
 require 'fluent/config'
+require 'fluent/config/element'
 
 module Fluent
   module Config
diff --git a/lib/fluent/config/element.rb b/lib/fluent/config/element.rb
index ba1f124621..5d47824646 100644
--- a/lib/fluent/config/element.rb
+++ b/lib/fluent/config/element.rb
@@ -14,9 +14,10 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/config/error'
+require 'fluent/config/error'
+require 'fluent/config/literal_parser'
 
+module Fluent
   module Config
     class Element < Hash
       def initialize(name, arg, attrs, elements, unused = nil)
diff --git a/lib/fluent/config/literal_parser.rb b/lib/fluent/config/literal_parser.rb
index b65479e098..403b7a12ee 100644
--- a/lib/fluent/config/literal_parser.rb
+++ b/lib/fluent/config/literal_parser.rb
@@ -14,13 +14,16 @@
 #    limitations under the License.
 #
 
-module Fluent
-  module Config
+require 'stringio'
+
+require 'json'
+require 'yajl'
+require 'irb/ruby-lex'  # RubyLex
 
-    require 'yajl'
-    require 'fluent/config/basic_parser'
-    require 'irb/ruby-lex'  # RubyLex
+require 'fluent/config/basic_parser'
 
+module Fluent
+  module Config
     class LiteralParser < BasicParser
       def self.unescape_char(c)
         case c
diff --git a/lib/fluent/config/parser.rb b/lib/fluent/config/parser.rb
index 6024f5d5b9..98e8cbfbec 100644
--- a/lib/fluent/config/parser.rb
+++ b/lib/fluent/config/parser.rb
@@ -14,11 +14,13 @@
 #    limitations under the License.
 #
 
+require 'uri'
+
+require 'fluent/config/error'
+require 'fluent/config/element'
+
 module Fluent
   module Config
-    require 'fluent/config/error'
-    require 'fluent/config/element'
-
     class Parser
       def self.parse(io, fname, basepath = Dir.pwd)
         attrs, elems = Parser.new(basepath, io.each_line, fname).parse!(true)
diff --git a/lib/fluent/config/section.rb b/lib/fluent/config/section.rb
index 8549e22fd3..0a0933201c 100644
--- a/lib/fluent/config/section.rb
+++ b/lib/fluent/config/section.rb
@@ -16,10 +16,10 @@
 
 require 'json'
 
-module Fluent
-  require 'fluent/config/error'
-  require 'fluent/config/v1_parser'
+require 'fluent/config/error'
+require 'fluent/config/v1_parser'
 
+module Fluent
   module Config
     class Section < BasicObject
       def self.name
diff --git a/lib/fluent/config/types.rb b/lib/fluent/config/types.rb
index 5442b66189..13af0b8264 100644
--- a/lib/fluent/config/types.rb
+++ b/lib/fluent/config/types.rb
@@ -14,9 +14,12 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'json'
+require 'json'
+
+require 'fluent/config/error'
+require 'fluent/configurable'
 
+module Fluent
   module Config
     def self.size_value(str)
       case str.to_s
diff --git a/lib/fluent/config/v1_parser.rb b/lib/fluent/config/v1_parser.rb
index 0303e9cd5f..4eceaedc3c 100644
--- a/lib/fluent/config/v1_parser.rb
+++ b/lib/fluent/config/v1_parser.rb
@@ -14,14 +14,16 @@
 #    limitations under the License.
 #
 
-module Fluent
-  module Config
+require 'strscan'
+require 'uri'
 
-    require 'strscan'
-    require 'fluent/config/error'
-    require 'fluent/config/literal_parser'
-    require 'fluent/config/element'
+require 'fluent/config/error'
+require 'fluent/config/basic_parser'
+require 'fluent/config/literal_parser'
+require 'fluent/config/element'
 
+module Fluent
+  module Config
     class V1Parser < LiteralParser
       ELEMENT_NAME = /[a-zA-Z0-9_]+/
 
diff --git a/lib/fluent/configurable.rb b/lib/fluent/configurable.rb
index 262e062690..16bc784d47 100644
--- a/lib/fluent/configurable.rb
+++ b/lib/fluent/configurable.rb
@@ -14,13 +14,13 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/config/configure_proxy'
-  require 'fluent/config/section'
-  require 'fluent/config/error'
-  require 'fluent/registry'
-  require 'fluent/plugin'
+require 'fluent/config/configure_proxy'
+require 'fluent/config/section'
+require 'fluent/config/error'
+require 'fluent/registry'
+require 'fluent/plugin'
 
+module Fluent
   module Configurable
     def self.included(mod)
       mod.extend(ClassMethods)
diff --git a/lib/fluent/engine.rb b/lib/fluent/engine.rb
index 2f942b3ef4..0e98c02494 100644
--- a/lib/fluent/engine.rb
+++ b/lib/fluent/engine.rb
@@ -14,12 +14,21 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/event_router'
-  require 'fluent/root_agent'
-  require 'fluent/time'
-  require 'fluent/system_config'
+require 'socket'
+require 'rubygems'
+
+require 'msgpack'
+require 'cool.io'
 
+require 'fluent/config'
+require 'fluent/event'
+require 'fluent/event_router'
+require 'fluent/root_agent'
+require 'fluent/time'
+require 'fluent/system_config'
+require 'fluent/plugin'
+
+module Fluent
   class EngineClass
     class DummyMessagePackFactory
       def packer(*args)
diff --git a/lib/fluent/event.rb b/lib/fluent/event.rb
index f07bfd1a1e..7152b2cd3a 100644
--- a/lib/fluent/event.rb
+++ b/lib/fluent/event.rb
@@ -14,6 +14,8 @@
 #    limitations under the License.
 #
 
+require 'fluent/engine'
+
 module Fluent
   class EventStream
     include Enumerable
diff --git a/lib/fluent/event_router.rb b/lib/fluent/event_router.rb
index 339e406292..7ff4828606 100644
--- a/lib/fluent/event_router.rb
+++ b/lib/fluent/event_router.rb
@@ -13,9 +13,11 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 #
-module Fluent
-  require 'fluent/match'
 
+require 'fluent/match'
+require 'fluent/event'
+
+module Fluent
   #
   # EventRouter is responsible to route events to a collector.
   #
diff --git a/lib/fluent/filter.rb b/lib/fluent/filter.rb
index b5da9c4982..86d6357f31 100644
--- a/lib/fluent/filter.rb
+++ b/lib/fluent/filter.rb
@@ -14,6 +14,12 @@
 #    limitations under the License.
 #
 
+require 'fluent/config'
+require 'fluent/configurable'
+require 'fluent/engine'
+require 'fluent/event'
+require 'fluent/log'
+
 module Fluent
   class Filter
     include Configurable
diff --git a/lib/fluent/formatter.rb b/lib/fluent/formatter.rb
index dbc4c86b4b..9bbaefd306 100644
--- a/lib/fluent/formatter.rb
+++ b/lib/fluent/formatter.rb
@@ -14,9 +14,11 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/registry'
+require 'fluent/configurable'
+require 'fluent/registry'
+require 'fluent/mixin'
 
+module Fluent
   class Formatter
     include Configurable
 
diff --git a/lib/fluent/input.rb b/lib/fluent/input.rb
index 10a6022bae..7de192019a 100644
--- a/lib/fluent/input.rb
+++ b/lib/fluent/input.rb
@@ -14,6 +14,11 @@
 #    limitations under the License.
 #
 
+require 'fluent/config'
+require 'fluent/configurable'
+require 'fluent/engine'
+require 'fluent/log'
+
 module Fluent
   class Input
     include Configurable
diff --git a/lib/fluent/label.rb b/lib/fluent/label.rb
index 2473832b27..d94f102089 100644
--- a/lib/fluent/label.rb
+++ b/lib/fluent/label.rb
@@ -14,9 +14,9 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/agent'
+require 'fluent/agent'
 
+module Fluent
   class Label < Agent
     def initialize(name, opts = {})
       super(opts)
diff --git a/lib/fluent/log.rb b/lib/fluent/log.rb
index 978da489d1..e0340497c0 100644
--- a/lib/fluent/log.rb
+++ b/lib/fluent/log.rb
@@ -65,6 +65,9 @@ def initialize(out=STDERR, level=LEVEL_TRACE, opts={})
       # TODO: This variable name is unclear so we should change to better name.
       @threads_exclude_events = []
 
+      # Fluent::Engine requires Fluent::Log, so we must take that object lazily
+      @engine = Fluent.const_get('Engine')
+
       if opts.has_key?(:suppress_repeated_stacktrace)
         @suppress_repeated_stacktrace = opts[:suppress_repeated_stacktrace]
       end
@@ -285,7 +288,7 @@ def event(level, args)
           record[key] = record[key].inspect unless record[key].respond_to?(:to_msgpack)
         }
         record['message'] = message.dup
-        Engine.push_log_event("#{@tag}.#{level}", time.to_i, record)
+        @engine.push_log_event("#{@tag}.#{level}", time.to_i, record)
       end
 
       return time, message
diff --git a/lib/fluent/mixin.rb b/lib/fluent/mixin.rb
index ff4b1680d1..a2e7ea3a63 100644
--- a/lib/fluent/mixin.rb
+++ b/lib/fluent/mixin.rb
@@ -14,10 +14,12 @@
 #    limitations under the License.
 #
 
+require 'fluent/timezone'
+require 'fluent/time'
+require 'fluent/config/error'
+
 module Fluent
   class TimeFormatter
-    require 'fluent/timezone'
-
     def initialize(format, localtime, timezone = nil)
       @tc1 = 0
       @tc1_str = nil
diff --git a/lib/fluent/output.rb b/lib/fluent/output.rb
index ebeea00c34..75cd27f9bf 100644
--- a/lib/fluent/output.rb
+++ b/lib/fluent/output.rb
@@ -14,6 +14,15 @@
 #    limitations under the License.
 #
 
+require 'thread'
+
+require 'fluent/config'
+require 'fluent/configurable'
+require 'fluent/engine'
+require 'fluent/log'
+require 'fluent/plugin'
+require 'fluent/timezone'
+
 module Fluent
   class OutputChain
     def initialize(array, tag, es, chain=NullOutputChain.instance)
@@ -93,7 +102,6 @@ def secondary_init(primary)
     end
   end
 
-
   class OutputThread
     def initialize(output)
       @output = output
diff --git a/lib/fluent/parser.rb b/lib/fluent/parser.rb
index ef14b46a09..dd933e358a 100644
--- a/lib/fluent/parser.rb
+++ b/lib/fluent/parser.rb
@@ -14,9 +14,19 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/registry'
+require 'time'
+require 'json'
+
+require 'yajl'
 
+require 'fluent/config/error'
+require 'fluent/config/element'
+require 'fluent/configurable'
+require 'fluent/engine'
+require 'fluent/registry'
+require 'fluent/time'
+
+module Fluent
   class ParserError < StandardError
   end
 
diff --git a/lib/fluent/plugin.rb b/lib/fluent/plugin.rb
index da26d4d67c..b4a4fbda41 100644
--- a/lib/fluent/plugin.rb
+++ b/lib/fluent/plugin.rb
@@ -14,6 +14,10 @@
 #    limitations under the License.
 #
 
+require 'rubygems'
+
+require 'fluent/config/error'
+
 module Fluent
   class PluginClass
     # This class is refactored using Fluent::Registry at v0.14
@@ -66,10 +70,12 @@ def new_buffer(type)
     end
 
     def new_parser(type)
+      require 'fluent/parser'
       TextParser.lookup(type)
     end
 
     def new_formatter(type)
+      require 'fluent/formatter'
       TextFormatter.lookup(type)
     end
 
diff --git a/lib/fluent/plugin/buf_file.rb b/lib/fluent/plugin/buf_file.rb
index c3285da110..02c018e976 100644
--- a/lib/fluent/plugin/buf_file.rb
+++ b/lib/fluent/plugin/buf_file.rb
@@ -14,6 +14,13 @@
 #    limitations under the License.
 #
 
+require 'fileutils'
+require 'uri'
+
+require 'fluent/env'
+require 'fluent/plugin'
+require 'fluent/buffer'
+
 module Fluent
   class FileBufferChunk < BufferChunk
     def initialize(key, path, unique_id, mode="a+", symlink_path = nil)
diff --git a/lib/fluent/plugin/buf_memory.rb b/lib/fluent/plugin/buf_memory.rb
index 7ed3a16d35..00b3b6f8a0 100644
--- a/lib/fluent/plugin/buf_memory.rb
+++ b/lib/fluent/plugin/buf_memory.rb
@@ -14,6 +14,12 @@
 #    limitations under the License.
 #
 
+require 'stringio'
+
+require 'fluent/engine'
+require 'fluent/plugin'
+require 'fluent/buffer'
+
 module Fluent
   class MemoryBufferChunk < BufferChunk
     def initialize(key, data='')
diff --git a/lib/fluent/plugin/exec_util.rb b/lib/fluent/plugin/exec_util.rb
index 9ed3d9edff..33548dd9ab 100644
--- a/lib/fluent/plugin/exec_util.rb
+++ b/lib/fluent/plugin/exec_util.rb
@@ -14,10 +14,15 @@
 #    limitations under the License.
 #
 
+require 'msgpack'
+require 'yajl'
+
+require 'fluent/engine'
+require 'fluent/plugin'
+require 'fluent/parser'
+
 module Fluent
   module ExecUtil
-    require 'fluent/parser'
-
     SUPPORTED_FORMAT = {
       'tsv' => :tsv,
       'json' => :json,
diff --git a/lib/fluent/plugin/filter_grep.rb b/lib/fluent/plugin/filter_grep.rb
index 95a21bcd3d..be8b61a2fa 100644
--- a/lib/fluent/plugin/filter_grep.rb
+++ b/lib/fluent/plugin/filter_grep.rb
@@ -14,6 +14,9 @@
 #    limitations under the License.
 #
 
+require 'fluent/filter'
+require 'fluent/config/error'
+
 module Fluent
   class GrepFilter < Filter
     Fluent::Plugin.register_filter('grep', self)
diff --git a/lib/fluent/plugin/filter_record_transformer.rb b/lib/fluent/plugin/filter_record_transformer.rb
index 3838c23700..36293d7e7d 100644
--- a/lib/fluent/plugin/filter_record_transformer.rb
+++ b/lib/fluent/plugin/filter_record_transformer.rb
@@ -14,17 +14,19 @@
 #    limitations under the License.
 #
 
+require 'socket'
+require 'json'
 require 'ostruct'
 
+require 'fluent/filter'
+require 'fluent/config/error'
+require 'fluent/event'
+require 'fluent/time'
+
 module Fluent
   class RecordTransformerFilter < Filter
     Fluent::Plugin.register_filter('record_transformer', self)
 
-    def initialize
-      require 'socket'
-      super
-    end
-
     desc 'A comma-delimited list of keys to delete.'
     config_param :remove_keys, :string, default: nil
     desc 'A comma-delimited list of keys to keep.'
diff --git a/lib/fluent/plugin/filter_stdout.rb b/lib/fluent/plugin/filter_stdout.rb
index 5ab0290a99..4fc14d4c43 100644
--- a/lib/fluent/plugin/filter_stdout.rb
+++ b/lib/fluent/plugin/filter_stdout.rb
@@ -14,6 +14,9 @@
 #    limitations under the License.
 #
 
+require 'fluent/filter'
+require 'fluent/plugin'
+
 module Fluent
   class StdoutFilter < Filter
     Plugin.register_filter('stdout', self)
diff --git a/lib/fluent/plugin/in_debug_agent.rb b/lib/fluent/plugin/in_debug_agent.rb
index 60a6ffea97..cfb196298b 100644
--- a/lib/fluent/plugin/in_debug_agent.rb
+++ b/lib/fluent/plugin/in_debug_agent.rb
@@ -14,6 +14,8 @@
 #    limitations under the License.
 #
 
+require 'fluent/input'
+
 module Fluent
   class DebugAgentInput < Input
     Plugin.register_input('debug_agent', self)
diff --git a/lib/fluent/plugin/in_dummy.rb b/lib/fluent/plugin/in_dummy.rb
index b436eb2210..365eb975f4 100644
--- a/lib/fluent/plugin/in_dummy.rb
+++ b/lib/fluent/plugin/in_dummy.rb
@@ -14,6 +14,11 @@
 #    limitations under the License.
 #
 
+require 'json'
+
+require 'fluent/input'
+require 'fluent/config/error'
+
 module Fluent
   class DummyInput < Input
     Fluent::Plugin.register_input('dummy', self)
diff --git a/lib/fluent/plugin/in_exec.rb b/lib/fluent/plugin/in_exec.rb
index b5ea3e3e97..b9274400ca 100644
--- a/lib/fluent/plugin/in_exec.rb
+++ b/lib/fluent/plugin/in_exec.rb
@@ -14,6 +14,13 @@
 #    limitations under the License.
 #
 
+require 'yajl'
+
+require 'fluent/input'
+require 'fluent/time'
+require 'fluent/timezone'
+require 'fluent/config/error'
+
 module Fluent
   class ExecInput < Input
     Plugin.register_input('exec', self)
@@ -21,7 +28,6 @@ class ExecInput < Input
     def initialize
       super
       require 'fluent/plugin/exec_util'
-      require 'fluent/timezone'
     end
 
     desc 'The command (program) to execute.'
diff --git a/lib/fluent/plugin/in_forward.rb b/lib/fluent/plugin/in_forward.rb
index c9d6d51a20..7a4c2189ea 100644
--- a/lib/fluent/plugin/in_forward.rb
+++ b/lib/fluent/plugin/in_forward.rb
@@ -14,6 +14,13 @@
 #    limitations under the License.
 #
 
+require 'fcntl'
+
+require 'cool.io'
+require 'yajl'
+
+require 'fluent/input'
+
 module Fluent
   class ForwardInput < Input
     Plugin.register_input('forward', self)
diff --git a/lib/fluent/plugin/in_gc_stat.rb b/lib/fluent/plugin/in_gc_stat.rb
index e0dbfdea41..22690f3e7e 100644
--- a/lib/fluent/plugin/in_gc_stat.rb
+++ b/lib/fluent/plugin/in_gc_stat.rb
@@ -14,6 +14,10 @@
 #    limitations under the License.
 #
 
+require 'cool.io'
+
+require 'fluent/input'
+
 module Fluent
   class GCStatInput < Input
     Plugin.register_input('gc_stat', self)
diff --git a/lib/fluent/plugin/in_http.rb b/lib/fluent/plugin/in_http.rb
index 255a5c5fe3..aee6c3a8fa 100644
--- a/lib/fluent/plugin/in_http.rb
+++ b/lib/fluent/plugin/in_http.rb
@@ -14,6 +14,16 @@
 #    limitations under the License.
 #
 
+require 'uri'
+require 'socket'
+require 'json'
+
+require 'cool.io'
+
+require 'fluent/input'
+require 'fluent/event'
+require 'fluent/process'
+
 module Fluent
   class HttpInput < Input
     Plugin.register_input('http', self)
@@ -24,7 +34,6 @@ class HttpInput < Input
 
     def initialize
       require 'webrick/httputils'
-      require 'uri'
       super
     end
 
diff --git a/lib/fluent/plugin/in_monitor_agent.rb b/lib/fluent/plugin/in_monitor_agent.rb
index 9ec0a5a1d7..e4389fc4ba 100644
--- a/lib/fluent/plugin/in_monitor_agent.rb
+++ b/lib/fluent/plugin/in_monitor_agent.rb
@@ -14,17 +14,20 @@
 #    limitations under the License.
 #
 
+require 'json'
+require 'webrick'
+require 'cgi'
+
+require 'cool.io'
+
+require 'fluent/input'
+require 'fluent/output'
+require 'fluent/filter'
+
 module Fluent
   class MonitorAgentInput < Input
     Plugin.register_input('monitor_agent', self)
 
-    require 'webrick'
-
-    def initialize
-      require 'cgi'
-      super
-    end
-
     config_param :bind, :string, default: '0.0.0.0'
     config_param :port, :integer, default: 24220
     config_param :tag, :string, default: nil
diff --git a/lib/fluent/plugin/in_object_space.rb b/lib/fluent/plugin/in_object_space.rb
index d29e90905d..e3c28399fb 100644
--- a/lib/fluent/plugin/in_object_space.rb
+++ b/lib/fluent/plugin/in_object_space.rb
@@ -14,6 +14,11 @@
 #    limitations under the License.
 #
 
+require 'cool.io'
+require 'yajl'
+
+require 'fluent/input'
+
 module Fluent
   class ObjectSpaceInput < Input
     Plugin.register_input('object_space', self)
diff --git a/lib/fluent/plugin/in_stream.rb b/lib/fluent/plugin/in_stream.rb
index d2f9c030aa..3f2d1fcba4 100644
--- a/lib/fluent/plugin/in_stream.rb
+++ b/lib/fluent/plugin/in_stream.rb
@@ -14,6 +14,15 @@
 #    limitations under the License.
 #
 
+require 'fileutils'
+require 'socket'
+
+require 'cool.io'
+require 'yajl'
+
+require 'fluent/input'
+require 'fluent/event'
+
 module Fluent
   # obsolete
   class StreamInput < Input
diff --git a/lib/fluent/plugin/in_syslog.rb b/lib/fluent/plugin/in_syslog.rb
index fc7d5e2b9d..0f4291fe65 100644
--- a/lib/fluent/plugin/in_syslog.rb
+++ b/lib/fluent/plugin/in_syslog.rb
@@ -14,6 +14,13 @@
 #    limitations under the License.
 #
 
+require 'cool.io'
+require 'yajl'
+
+require 'fluent/input'
+require 'fluent/config/error'
+require 'fluent/parser'
+
 module Fluent
   class SyslogInput < Input
     Plugin.register_input('syslog', self)
@@ -60,7 +67,6 @@ class SyslogInput < Input
 
     def initialize
       super
-      require 'cool.io'
       require 'fluent/plugin/socket_util'
     end
 
diff --git a/lib/fluent/plugin/in_tail.rb b/lib/fluent/plugin/in_tail.rb
index fc8c51ac47..b5fb28bf7d 100644
--- a/lib/fluent/plugin/in_tail.rb
+++ b/lib/fluent/plugin/in_tail.rb
@@ -14,6 +14,12 @@
 #    limitations under the License.
 #
 
+require 'cool.io'
+
+require 'fluent/input'
+require 'fluent/config/error'
+require 'fluent/event'
+
 module Fluent
   class NewTailInput < Input
     Plugin.register_input('tail', self)
diff --git a/lib/fluent/plugin/in_tcp.rb b/lib/fluent/plugin/in_tcp.rb
index df02c5ecbf..cfac648bf9 100644
--- a/lib/fluent/plugin/in_tcp.rb
+++ b/lib/fluent/plugin/in_tcp.rb
@@ -14,6 +14,8 @@
 #    limitations under the License.
 #
 
+require 'cool.io'
+
 require 'fluent/plugin/socket_util'
 
 module Fluent
diff --git a/lib/fluent/plugin/out_copy.rb b/lib/fluent/plugin/out_copy.rb
index de43630589..c26804b218 100644
--- a/lib/fluent/plugin/out_copy.rb
+++ b/lib/fluent/plugin/out_copy.rb
@@ -14,6 +14,10 @@
 #    limitations under the License.
 #
 
+require 'fluent/output'
+require 'fluent/config/error'
+require 'fluent/event'
+
 module Fluent
   class CopyOutput < MultiOutput
     Plugin.register_output('copy', self)
diff --git a/lib/fluent/plugin/out_exec.rb b/lib/fluent/plugin/out_exec.rb
index 2062afda51..653686bf3e 100644
--- a/lib/fluent/plugin/out_exec.rb
+++ b/lib/fluent/plugin/out_exec.rb
@@ -14,6 +14,10 @@
 #    limitations under the License.
 #
 
+require 'tempfile'
+
+require 'fluent/output'
+require 'fluent/config/error'
 require 'fluent/plugin/exec_util'
 
 module Fluent
@@ -22,7 +26,6 @@ class ExecOutput < TimeSlicedOutput
 
     def initialize
       super
-      require 'tempfile'
       @localtime = false
     end
 
diff --git a/lib/fluent/plugin/out_exec_filter.rb b/lib/fluent/plugin/out_exec_filter.rb
index 46021c37bc..4e549a84fe 100644
--- a/lib/fluent/plugin/out_exec_filter.rb
+++ b/lib/fluent/plugin/out_exec_filter.rb
@@ -14,7 +14,14 @@
 #    limitations under the License.
 #
 
+require 'yajl'
+
+require 'fluent/output'
+require 'fluent/env'
+require 'fluent/time'
+require 'fluent/timezone'
 require 'fluent/plugin/exec_util'
+require 'fluent/config/error'
 
 module Fluent
   class ExecFilterOutput < BufferedOutput
diff --git a/lib/fluent/plugin/out_file.rb b/lib/fluent/plugin/out_file.rb
index 08e355cd5c..d2d795acad 100644
--- a/lib/fluent/plugin/out_file.rb
+++ b/lib/fluent/plugin/out_file.rb
@@ -14,6 +14,12 @@
 #    limitations under the License.
 #
 
+require 'fileutils'
+require 'zlib'
+
+require 'fluent/output'
+require 'fluent/config/error'
+
 module Fluent
   class FileOutput < TimeSlicedOutput
     Plugin.register_output('file', self)
diff --git a/lib/fluent/plugin/out_forward.rb b/lib/fluent/plugin/out_forward.rb
index 3063b8caa6..57d747095a 100644
--- a/lib/fluent/plugin/out_forward.rb
+++ b/lib/fluent/plugin/out_forward.rb
@@ -14,6 +14,15 @@
 #    limitations under the License.
 #
 
+require 'base64'
+require 'socket'
+require 'fileutils'
+
+require 'cool.io'
+
+require 'fluent/output'
+require 'fluent/config/error'
+
 module Fluent
   class ForwardOutputError < StandardError
   end
@@ -29,9 +38,6 @@ class ForwardOutput < ObjectBufferedOutput
 
     def initialize
       super
-      require "base64"
-      require 'socket'
-      require 'fileutils'
       require 'fluent/plugin/socket_util'
       @nodes = []  #=> [Node]
     end
diff --git a/lib/fluent/plugin/out_null.rb b/lib/fluent/plugin/out_null.rb
index e60ab03af0..032f683a99 100644
--- a/lib/fluent/plugin/out_null.rb
+++ b/lib/fluent/plugin/out_null.rb
@@ -14,6 +14,8 @@
 #    limitations under the License.
 #
 
+require 'fluent/output'
+
 module Fluent
   class NullOutput < Output
     Plugin.register_output('null', self)
diff --git a/lib/fluent/plugin/out_relabel.rb b/lib/fluent/plugin/out_relabel.rb
index 82196b43f3..9622e66f29 100644
--- a/lib/fluent/plugin/out_relabel.rb
+++ b/lib/fluent/plugin/out_relabel.rb
@@ -14,6 +14,8 @@
 #    limitations under the License.
 #
 
+require 'fluent/output'
+
 module Fluent
   class RelabelOutput < Output
     Plugin.register_output('relabel', self)
diff --git a/lib/fluent/plugin/out_roundrobin.rb b/lib/fluent/plugin/out_roundrobin.rb
index 34212b4bc9..a17195ea21 100644
--- a/lib/fluent/plugin/out_roundrobin.rb
+++ b/lib/fluent/plugin/out_roundrobin.rb
@@ -14,6 +14,9 @@
 #    limitations under the License.
 #
 
+require 'fluent/output'
+require 'fluent/config/error'
+
 module Fluent
   class RoundRobinOutput < MultiOutput
     Plugin.register_output('roundrobin', self)
diff --git a/lib/fluent/plugin/out_stdout.rb b/lib/fluent/plugin/out_stdout.rb
index fbaa700622..47968d3481 100644
--- a/lib/fluent/plugin/out_stdout.rb
+++ b/lib/fluent/plugin/out_stdout.rb
@@ -14,6 +14,8 @@
 #    limitations under the License.
 #
 
+require 'fluent/output'
+
 module Fluent
   class StdoutOutput < Output
     Plugin.register_output('stdout', self)
diff --git a/lib/fluent/plugin/out_stream.rb b/lib/fluent/plugin/out_stream.rb
index 2ee222010b..d66d2d53d2 100644
--- a/lib/fluent/plugin/out_stream.rb
+++ b/lib/fluent/plugin/out_stream.rb
@@ -14,15 +14,15 @@
 #    limitations under the License.
 #
 
+require 'socket'
+require 'fileutils'
+
+require 'fluent/output'
+require 'fluent/event'
+
 module Fluent
   # obsolete
   class StreamOutput < BufferedOutput
-    def initialize
-      require 'socket'
-      require 'fileutils'
-      super
-    end
-
     config_param :send_timeout, :time, default: 60
 
     def configure(conf)
diff --git a/lib/fluent/plugin/socket_util.rb b/lib/fluent/plugin/socket_util.rb
index 7b9829e879..c5fb7ad98c 100644
--- a/lib/fluent/plugin/socket_util.rb
+++ b/lib/fluent/plugin/socket_util.rb
@@ -14,13 +14,15 @@
 #    limitations under the License.
 #
 
+require 'ipaddr'
+
 require 'cool.io'
 
+require 'fluent/plugin'
+
 module Fluent
   module SocketUtil
     def create_udp_socket(host)
-      require 'ipaddr'
-
       if IPAddr.new(IPSocket.getaddress(host)).ipv4?
         UDPSocket.new
       else
diff --git a/lib/fluent/process.rb b/lib/fluent/process.rb
index d2f87a0351..87151f8a48 100644
--- a/lib/fluent/process.rb
+++ b/lib/fluent/process.rb
@@ -14,6 +14,12 @@
 #    limitations under the License.
 #
 
+require 'thread'
+
+require 'fluent/config'
+require 'fluent/engine'
+require 'fluent/event'
+
 module Fluent
   class DetachProcessManager
     require 'singleton'
diff --git a/lib/fluent/registry.rb b/lib/fluent/registry.rb
index e5e1c87188..2500db891c 100644
--- a/lib/fluent/registry.rb
+++ b/lib/fluent/registry.rb
@@ -14,9 +14,11 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/config/error'
+require 'rubygems'
+
+require 'fluent/config/error'
 
+module Fluent
   class Registry
     def initialize(kind, search_prefix)
       @kind = kind
diff --git a/lib/fluent/root_agent.rb b/lib/fluent/root_agent.rb
index 147cea094b..35857652f8 100644
--- a/lib/fluent/root_agent.rb
+++ b/lib/fluent/root_agent.rb
@@ -13,14 +13,17 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 #
-module Fluent
 
-  require 'delegate'
+require 'delegate'
 
-  require 'fluent/agent'
-  require 'fluent/label'
-  require 'fluent/system_config'
+require 'fluent/config/error'
+require 'fluent/agent'
+require 'fluent/engine'
+require 'fluent/label'
+require 'fluent/plugin'
+require 'fluent/system_config'
 
+module Fluent
   #
   # Fluentd forms a tree structure to manage plugins:
   #
diff --git a/lib/fluent/rpc.rb b/lib/fluent/rpc.rb
index 2c7e70a16c..53b899ad81 100644
--- a/lib/fluent/rpc.rb
+++ b/lib/fluent/rpc.rb
@@ -14,10 +14,10 @@
 #    limitations under the License.
 #
 
+require 'webrick'
+
 module Fluent
   module RPC
-    require 'webrick'
-
     class Server
       def initialize(endpoint, log)
         bind, port = endpoint.split(':')
diff --git a/lib/fluent/supervisor.rb b/lib/fluent/supervisor.rb
index d09883bc23..65712fa669 100644
--- a/lib/fluent/supervisor.rb
+++ b/lib/fluent/supervisor.rb
@@ -14,10 +14,16 @@
 #    limitations under the License.
 #
 
-require 'fluent/load'
-require 'fluent/system_config'
 require 'etc'
 
+require 'fluent/config'
+require 'fluent/env'
+require 'fluent/engine'
+require 'fluent/log'
+require 'fluent/plugin'
+require 'fluent/rpc'
+require 'fluent/system_config'
+
 module Fluent
   class Supervisor
     def self.get_etc_passwd(user)
@@ -468,40 +474,6 @@ def read_config
       @conf = Fluent::Config.parse(@config_data, @config_fname, @config_basedir, @use_v1_config)
     end
 
-    class SystemConfig
-      include Configurable
-
-      config_param :log_level, default: nil do |level|
-        Log.str_to_level(level)
-      end
-      config_param :suppress_repeated_stacktrace, :bool, default: nil
-      config_param :emit_error_log_interval, :time, default: nil
-      config_param :suppress_config_dump, :bool, default: nil
-      config_param :without_source, :bool, default: nil
-      config_param :rpc_endpoint, :string, default: nil
-      config_param :enable_get_dump, :bool, default: nil
-      config_param :process_name, default: nil
-
-      def initialize(conf)
-        super()
-        configure(conf)
-      end
-
-      def apply(supervisor)
-        system = self
-        supervisor.instance_eval {
-          @log.level = @log_level = system.log_level unless system.log_level.nil?
-          @suppress_interval = system.emit_error_log_interval unless system.emit_error_log_interval.nil?
-          @suppress_config_dump = system.suppress_config_dump unless system.suppress_config_dump.nil?
-          @suppress_repeated_stacktrace = system.suppress_repeated_stacktrace unless system.suppress_repeated_stacktrace.nil?
-          @without_source = system.without_source unless system.without_source.nil?
-          @rpc_endpoint = system.rpc_endpoint unless system.rpc_endpoint.nil?
-          @enable_get_dump = system.enable_get_dump unless system.enable_get_dump.nil?
-          @process_name = system.process_name unless system.process_name.nil?
-        }
-      end
-    end
-
     def run_configure
       Fluent::Engine.run_configure(@conf)
     end
diff --git a/lib/fluent/system_config.rb b/lib/fluent/system_config.rb
index 4452e9dd86..e7d252c864 100644
--- a/lib/fluent/system_config.rb
+++ b/lib/fluent/system_config.rb
@@ -14,9 +14,10 @@
 #    limitations under the License.
 #
 
-module Fluent
-  require 'fluent/configurable'
+require 'fluent/configurable'
+require 'fluent/config/element'
 
+module Fluent
   module SystemConfigMixin
     def system_config
       @_system_config || Fluent::Engine.system_config
@@ -56,8 +57,13 @@ def self.create(conf)
       SystemConfig.new(systems.first)
     end
 
-    def initialize(conf={})
+    def self.blank_system_config
+      Fluent::Config::Element.new('<SYSTEM>', '', {}, [])
+    end
+
+    def initialize(conf=nil)
       super()
+      conf ||= SystemConfig.blank_system_config
       configure(conf)
     end
 
diff --git a/lib/fluent/test.rb b/lib/fluent/test.rb
index f552f7a20d..d34b4442f7 100644
--- a/lib/fluent/test.rb
+++ b/lib/fluent/test.rb
@@ -15,7 +15,7 @@
 #
 
 require 'test/unit'
-require 'fluent/load'
+require 'fluent/env' # for Fluent.windows?
 require 'fluent/test/base'
 require 'fluent/test/input_test'
 require 'fluent/test/output_test'
diff --git a/lib/fluent/test/base.rb b/lib/fluent/test/base.rb
index 8c40ac77ce..713a944ad3 100644
--- a/lib/fluent/test/base.rb
+++ b/lib/fluent/test/base.rb
@@ -14,6 +14,10 @@
 #    limitations under the License.
 #
 
+require 'fluent/engine'
+require 'fluent/system_config'
+require 'fluent/config'
+
 module Fluent
   module Test
     def self.setup
diff --git a/lib/fluent/test/filter_test.rb b/lib/fluent/test/filter_test.rb
index 2a55bee08a..88cca149d6 100644
--- a/lib/fluent/test/filter_test.rb
+++ b/lib/fluent/test/filter_test.rb
@@ -14,6 +14,9 @@
 #    limitations under the License.
 #
 
+require 'fluent/test/base'
+require 'fluent/event'
+
 module Fluent
   module Test
     class FilterTestDriver < TestDriver
diff --git a/lib/fluent/test/formatter_test.rb b/lib/fluent/test/formatter_test.rb
index f840cebf52..d7bd2a888c 100644
--- a/lib/fluent/test/formatter_test.rb
+++ b/lib/fluent/test/formatter_test.rb
@@ -14,10 +14,11 @@
 #    limitations under the License.
 #
 
+require 'fluent/formatter'
+require 'fluent/config'
+
 module Fluent
   module Test
-    require 'fluent/config'
-
     class FormatterTestDriver
       def initialize(klass_or_str, proc=nil, &block)
         if klass_or_str.is_a?(Class)
diff --git a/lib/fluent/test/input_test.rb b/lib/fluent/test/input_test.rb
index 341211cd5f..f0c0c90bff 100644
--- a/lib/fluent/test/input_test.rb
+++ b/lib/fluent/test/input_test.rb
@@ -14,6 +14,11 @@
 #    limitations under the License.
 #
 
+require 'fluent/buffer'
+require 'fluent/engine'
+require 'fluent/time'
+require 'fluent/test/base'
+
 module Fluent
   class FileBuffer < BasicBuffer
     def self.clear_buffer_paths
diff --git a/lib/fluent/test/output_test.rb b/lib/fluent/test/output_test.rb
index 83d749e94a..62b971a2f0 100644
--- a/lib/fluent/test/output_test.rb
+++ b/lib/fluent/test/output_test.rb
@@ -14,6 +14,10 @@
 #    limitations under the License.
 #
 
+require 'fluent/engine'
+require 'fluent/event'
+require 'fluent/test/input_test'
+
 module Fluent
   module Test
     class TestOutputChain
diff --git a/lib/fluent/test/parser_test.rb b/lib/fluent/test/parser_test.rb
index 7c6f6ddd6b..79706c192f 100644
--- a/lib/fluent/test/parser_test.rb
+++ b/lib/fluent/test/parser_test.rb
@@ -14,10 +14,11 @@
 #    limitations under the License.
 #
 
+require 'fluent/parser'
+require 'fluent/config'
+
 module Fluent
   module Test
-    require 'fluent/config'
-
     class ParserTestDriver
       def initialize(klass_or_str, format=nil, conf={}, &block)
         if klass_or_str.is_a?(Class)
diff --git a/lib/fluent/timezone.rb b/lib/fluent/timezone.rb
index 4320a728d0..f0383495be 100644
--- a/lib/fluent/timezone.rb
+++ b/lib/fluent/timezone.rb
@@ -16,6 +16,8 @@
 
 require 'tzinfo'
 
+require 'fluent/config/error'
+
 module Fluent
   class Timezone
     # [+-]HH:MM, [+-]HHMM, [+-]HH
diff --git a/test/plugin/test_in_forward.rb b/test/plugin/test_in_forward.rb
index b103d8d3e7..c68a73a374 100644
--- a/test/plugin/test_in_forward.rb
+++ b/test/plugin/test_in_forward.rb
@@ -1,7 +1,11 @@
 require_relative '../helper'
+
 require 'fluent/test'
 require 'base64'
 
+require 'fluent/env'
+require 'fluent/plugin/in_forward'
+
 class ForwardInputTest < Test::Unit::TestCase
   def setup
     Fluent::Test.setup
diff --git a/test/test_event_router.rb b/test/test_event_router.rb
index 3e2ff61f96..cc2bd88c45 100644
--- a/test/test_event_router.rb
+++ b/test/test_event_router.rb
@@ -1,3 +1,4 @@
+require_relative 'helper'
 require 'fluent/event_router'
 require_relative 'test_plugin_classes'
 
diff --git a/test/test_plugin_classes.rb b/test/test_plugin_classes.rb
index 77e8c39e30..70cc9416ac 100644
--- a/test/test_plugin_classes.rb
+++ b/test/test_plugin_classes.rb
@@ -1,4 +1,7 @@
 require_relative 'helper'
+require 'fluent/input'
+require 'fluent/output'
+require 'fluent/filter'
 
 module FluentTest
   class FluentTestInput < ::Fluent::Input
diff --git a/test/test_process.rb b/test/test_process.rb
index ae846c3529..7c8c2a072b 100644
--- a/test/test_process.rb
+++ b/test/test_process.rb
@@ -1,6 +1,7 @@
 require_relative 'helper'
 require 'fluent/test'
 require 'fluent/event'
+require 'fluent/process'
 require 'stringio'
 require 'msgpack'
 
diff --git a/test/test_root_agent.rb b/test/test_root_agent.rb
index 50ff51b55e..8357a683f7 100644
--- a/test/test_root_agent.rb
+++ b/test/test_root_agent.rb
@@ -1,3 +1,4 @@
+require_relative 'helper'
 require 'fluent/event_router'
 require 'fluent/system_config'
 require_relative 'test_plugin_classes'