对付qihoo.net时出现ActionController::DoubleRenderError

对于流氓，最好的处理方法是封杀之。
我的做法是：
在ApplicationController中加上如下代码：

before_filter :init

def init
  init_bot
  ...
end

def init_bot
  blocked_bots = ["qihoo.net"...]
  blocked_bots.each do
    |bot|
    if request.env["HTTP_USER_AGENT"] and request.env["HTTP_USER_AGENT"].downcase.include?(bot.downcase)
      render :text => ""
      return
    end
  end
end

这样的处理方法对于别的一些爬虫没有问题，但是遇到qihoo却会出错，搞得邮箱中一大堆错误报告:

A ActionController::DoubleRenderError occurred in ...:

Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and at most once per action. Also note that neither redirect nor render terminate execution of the action, so if you want to exit an action after redirecting, you need to do something like "redirect_to(...) and return".
/usr/local/ruby/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:1136:in `redirect_to_full_url'
...
* HTTP_USER_AGENT                             : Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; CollapsarWEB qihoobot@qihoo.net)
...

直接在web server上面封就好了，没必要用rails写程序处理。

return只是跳出这个方法，换用exit就可以了

错误在于你的代码本身。既然 init_bot 是个 before_filter 那就应该 return false

nginx:

            if ($http_user_agent ~* "qihoobot") {
                return 403;
            }