def logger
  request.logger
end

def logger; get_header(RACK_LOGGER) end

def get_header(name)
  @env[name]
end

RACK_LOGGER = 'rack.logger'.freeze

# Rack::Logger
require 'logger'

module Rack
  # Sets up rack.logger to write to rack.errors stream
  class Logger
    def initialize(app, level = ::Logger::INFO)
      @app, @level = app, level
    end

    def call(env)
      logger = ::Logger.new(env[RACK_ERRORS])
      logger.level = @level

      env[RACK_LOGGER] = logger
      @app.call(env)
    end
  end
end

# Rack::NullLogger
module Rack
  class NullLogger
    def initialize(app)
      @app = app
    end

    def call(env)
      env[RACK_LOGGER] = self
      @app.call(env)
    end
    ...........

env.update(
  RACK_VERSION => Rack::VERSION,
  RACK_INPUT => rack_input,
  RACK_ERRORS => $stderr,
  RACK_MULTITHREAD => true,
  RACK_MULTIPROCESS => false,
  RACK_RUNONCE => false,
  RACK_URL_SCHEME => ["yes", "on", "1"].include?(env[HTTPS]) ? "https" : "http",
  RACK_IS_HIJACK => true,
  RACK_HIJACK => lambda { raise NotImplementedError, "only partial hijack is supported."},
  RACK_HIJACK_IO => nil
)

def logger
  return @logger unless @logger.nil?
  file = File.new("#{settings.root}/log/#{settings.environment}.log", 'a+')
  file.sync = true
  @logger = ::Logger.new(file)
end

logger.info "Hello"