clean_cookies.rb

# Rack middleware that drops non properly encoded cookies that would hurt the ActionDispatch::Cookies middleware.
#
# This is actually a hotfix for issues
#  * https://github.com/rack/rack/issues/225
#  * https://github.com/rails/rails/issues/2622
module CleanCookies
  # Tests whether a string may be decoded as a form component
  def decodable?(string)
    URI.decode_www_form_component(string)
    true
  rescue ArgumentError => e
    /^invalid %-encoding \(.*\)$/.match(e.message) ? false : raise
  end
  module_function :decodable?

  # Tests whether a cookie is clean, that is its key and value may be decoded as a form components
  def clean?(cookie)
    key, value = cookie.split('=', 2)
    decodable?(key) && decodable?(value)
  end
  module_function :clean?

  class Rack
    def initialize(app)
      @app = app
    end

    def call(env)
      if env['HTTP_COOKIE']
        clean_cookies, dirty_cookies = [], []

        # Split cookies into clean and dirty
        env['HTTP_COOKIE'].split(/[;,] */n).each do |cookie|
          if CleanCookies::clean?(cookie)
            clean_cookies << cookie
          else
            dirty_cookies << cookie
          end
        end

        # Keep only clean cookies
        env['HTTP_COOKIE'] = clean_cookies.join('; ')

        # Inform about dropped dirty cookies
        unless dirty_cookies.empty?
          env['rack.errors'].puts "Ignoring dirty cookies: #{dirty_cookies.inspect}"
        end
      end

      # Carry on
      @app.call(env)
    end
  end
end

# Automatically insert self in a Rails 3 middleware stack
if defined?(Rails.configuration) && Rails.configuration.respond_to?(:middleware)
  Rails.configuration.middleware.insert_before ActionDispatch::Cookies, CleanCookies::Rack
end

查看cookie引起的500数量：grep "cannot parse Cookie header" log/production.log |wc -l

aa = "%u60A8%u597D%uFF0C%u8BF7%u95EE%u6709%u4EC0%u4E48%u53EF%u4EE5%u5E2E%u5230%u60A8%uFF1F%u8BF7%u9009%u62E9%u60A8%u8981%u54A8%u8BE2%u7684%u5BA2%u670D%uFF01"

unescape(aa)
=> "您好，请问有什么可以帮到您？请选择您要咨询的客服！"