fluentd.confを内部DSLで生成

conf.rb

#!/usr/bin/env ruby
# coding: utf-8

require "./fluentd_conf_dsl"

# CONSTANTS
DOMAIN = "fluentd-01"

# MACRO
def macro_forward_settings
  type "forward"
  send_timeout "60s"
  recover_wait "10s"
  heartbeat_interval "1s"
  phi_threshold "8"
  server do
    name "#{DOMAIN}"
    host "#{DOMAIN}.example.com"
    port "24224"
  end
end

# DSL START
source do
  type "forward"
  port "24224"
  bind "0.0.0.0"
end
source do
  type "http"
  port "9880"
  bind "0.0.0.0"
  body_size_limit "1m"
  keepalive_timeout "10s"
end
match "**" do
  macro_forward_settings
  secondary do
    macro_forward_settings
  end
end

fluentd_conf_dsl.rb

#!/usr/bin/env ruby
# coding: utf-8

module FluentdConfDSL

  class Conf
    def initialize
      @current = Element.new
      @level = -1
    end
    def consume(id, *args, &block)
      @level += 1
      if block_given?
        parent = @current
        parent.push(@current = Tag.new(id.to_s, args, @level))
        yield
        @current = parent
      else
        @current.push KeyVal.new(id.to_s, args[0], @level)
      end
      @level -= 1
    end
    def to_s
      @current.to_s
    end
  end

  class Element
    def elements
      @elements ||= []
    end
    def push(element)
      elements.push element
    end
    def indent
      "  " * @level
    end
    def to_s
      elements.join "\n"
    end
  end

  class Tag < Element
    def initialize(name, args, level)
      @name = name
      @tag = args[0]
      @level = level
    end
    def tag
      if @tag.nil? then "" else " #{@tag}" end
    end
    def to_s
      "#{indent}<#{@name}#{tag}>\n#{elements.join("\n")}\n#{indent}</#{@name}>"
    end
  end

  class KeyVal < Element
    def initialize(key, val, level)
      @key = key
      @val = val
      @level = level
    end
    def to_s
      "#{indent}#{@key} #{@val}"
    end
  end

end

@output_file = false
@conf = FluentdConfDSL::Conf.new
at_exit { puts @conf.to_s unless @output_file }

@handle_dsl = false
alias :method_missing_org :method_missing
def method_missing(id, *args, &block)
  if id.to_s == "output_file"
    @output_file = true
    @conf = FluentdConfDSL::Conf.new
    yield
    File.open("./#{args[0]}", 'w') do |io|
      io.puts @conf.to_s
    end
    puts "[INFO] create #{args[0]}"
    puts @conf.to_s
  elsif @handle_dsl or %w|source match|.include?(id.to_s)
    @handle_dsl = true
    @conf.consume(id, *args, &block)
  else
    method_missing_org(id, *args, &block)
  end
end

メインを修正したので$ ./conf.rbでおk