Rails: How can I log all requests which take more than 4s to execute?

I have a web app hosted in a cloud environment which can be expanded to multiple web-nodes to serve higher load.

What I need to do is to catch this situation when we get more and more HTTP requests (assets are stored remotely). How can I do that?

The problem I see from this point of view is that if we have more requests than mongrel cluster can handle then the queue will grow. And in our Rails app we can only count only after mongrel will receive the request from balancer..

Any recommend开发者_高级运维ations?

I would start with an around_filter maybe something like:

around_filter :time_it

private
  def time_it
    now = DateTime.now
    yield # this is where the request gets made.
    time_span = DateTime.now - now

    # convert to double for better accuracy.
    # (i.e. 3.5 => 4 so you might not want to
    # work with integers here.
    if time_span * 86400.0 > 4.0  
      logger.debug "something is taking a little longer then expected here!"
    end
  end

Use this as a starting point. Hope that helps.

Edit: put this code in the ApplicationController so it can be used by every Controller.

In addition to @DJTripleThreat, you should have a look at NewRelic RPM to get more insight to your code's performance.