Using a ActionController::Caching::Sweeper didn’t run for updates on the models (even though it should work for non-Mongoid-models), so I ended up using a Mongoid::Observer to invalidate the cache when a model was updated.

To seperate the observers from the models, I created a app/observers directory and used the following code to automatically load the observers:

# mongoid observers/sweepers
config.mongoid.observers = Dir["#{config.root}/app/observers/*.rb"].collect do |full_name|
  File.basename(full_name,'.rb').to_sym
end

This is the app/observers/city_observer.rb file:

class CityObserver < Mongoid::Observer
  def after_create(city)
    expire_cache_for(city)
  end

  def after_update(city)
    expire_cache_for(city)
  end

  def after_destroy(city)
    expire_cache_for(city)
  end

  private

  def expire_cache_for(city)
    # expire fragments/pages for city
    @c ||= ActionController::Base.new

    @c.expire_fragment("city_#{city.id.to_s}")
    if city.state.present?
      @c.expire_fragment("state_#{city.state.id.to_s}")
    end
    if city.country.present?
      @c.expire_fragment("country_#{city.country.id.to_s}")
    end

    # and expire the continent page cache
    @c.expire_page("/continents/#{city.country.continent.slug}")
  end
end

Since the expire_fragment/expire_page functions are not defined in the observer, I create a ActionController::Base object to call them on that.

With this, a model update expires cached pages

#!/bin/bash
exec ssh -t `basename $BASH_SOURCE` screen -DR ; exit

The filename should be the servername to connect to, you can use ~/.ssh/config to define short aliases for your servers:

Host myshortalias HostName long.hostname.tld User ausername

This allows you to do ssh myshortalias to connect to the server in question. So, to connect to this server, name the file in ~/bin/Terminals myshortalias.
Make the myshortalias file executable: chmod 755 myshortalias
Try to open a connection via the myshortalias file: ./myshortalias — if this fails, you problably don’t have screen installed on the server – I really recommend to install it.
OK, if that works, disconnect from the server, and open the Butler Configuration.
Expand the “Hidden” elements, if they are not visible. Select “Add File” from the plus button. Navigate to the ~/bin/ folder and select the “Terminals” folder to add it to the Butler Configuration.
Select the “Terminals” container, open the “Triggers” tab, assign a Hot Key, change mode to “Opens a menu near the mouse”.
Select the “Terminals” folder, select the “Menu Filter” tab, change ‘Menus show…’ to “this folder’s content with X levels of recursion”, activate “Translate subfolders into menus”.
Select the “Options” tab and change the ‘Open with…’ setting to “Terminal” (or iTerm or …).
Pressing your hot key should now show a menu with the myshortalias script. You can add subfolders to the ~/bin/Terminals folder to group your servers. To add a server, just copy (or even better: hard-link) the myshortalias file to a new name which corresponds to a Host config in ~/.ssh/config.

Auf meinem Balkon

… wächst hier einiges.