Rails: filter defined in lib file required in environment.rb disappears from filter_chain in production environment. Why?

Question

Hi,

In my rails application, I have a file in lib that, among other things, sets up a filter that runs on all controllers.

When running under development environment, everything runs fine. However, under production the filter goes missing. Funny thing is, by inspecting the filter_chain, I noticed other filters remain, eg. those defined in plugins, or later in the specific controller class.

I've tested this with both rails edge and v2.3.0.

Testing update:

I've now tested with older rails and found the issue to be present back to v2.1.0, but not in v2.0.5, I've bisect them and found the 986aec5 rails commit to be guilty.

---

I've isolated the behavior to the following tiny test case:

# app/controllers/foo_controller.rb
class FooController < ApplicationController
  def index
    render :text => 'not filtered'
  end
end

# lib/foobar.rb
ActionController::Base.class_eval do
  before_filter :foobar
  def foobar
    render :text => 'hi from foobar filter'
  end
end

# config/environment.rb (at end of file)
require 'foobar'

---

Here's the output I get when running under the development environment:

$ script/server &
$ curl localhost:3000/foo
> hi from foobar filter

And here's the output for the production environment:

$ script/server -e production &
$ curl localhost:3000/foo             
> not filtered

---

As alluded to before, it works fine for any environment when I do the same thing via plugin. All I need is to put what's under lib/foobar.rb in the plugin's init.rb file.

So in a way I already have a workaround, but I'd like to understand what's going on and what's causing the filter to go missing when in production.

I conjecture it's something in the different ways Rails handles loading in the different environments, but I need to dig deeper.

update

Indeed, I've now narrowed it down to the following config line:

config.cache_classes = false

If, in production.rb, config.cache_classes is changed from true to false, the test application works properly.

I still wonder why class reloading is causing such thing.

Answer 1

Frederick Cheung on the Rails list had the answer:

Because cache_classes does a little more than just that. The way before filters work, if Foo < Bar then only those filters defined in Bar at that point will be inherited by Foo - adding them to Bar at a later date will not do anythingn

In development mode, the app starts, your file is required, the filter added to ActionController::Base. Later the first request comes along, the controller is loaded and it inherits that filter.

When cache_classes is true then all of your application classes are loaded ahead of time. This happens before your file is required, so all of your controllers already exist when that file is run and so it has no effect. You could solve this by requiring this file from an initializer (ensuring it runs before app classes are loaded), but really why wouldn;t you just put this in application.rb ?

Fred

---

My real case was actually way more involved, and this is the way I found to solve the issue:

config.after_initialize do
  require 'foobar'
end

The after_initialize block runs after the framework has been initialized but before it loads the application files, hence, it'll affect ActionPack::Base after it's been loaded, but before the application controllers are.

I guess that's the generally safe way to deal with all the preloading that goes on in production.

Answer 2

Drop a ruby script in

RAILS_ROOT\config\initializers

that contains

require "foobar.rb"

This invokes the before_filter for me.