Question

I am trying to cache a partial which is rendered in a layout. This partial is computationally expensive so I only want to compute it once. It is not controller specific so the usual fragment caching doesn’t seem to apply. I decided to use Rails.cache.fetch(‘menu’) for the caching instead. Here is what the contents of the partial look like.

<% Rails.cache.fetch('menu') do %>
  Partial code...
<% end %>

But when I do this it renders the partial twice. For some reason it stopped doing this in my development environment so I decided to try and deploy it. I am not so lucky with my production environment. The partial itself generates a menu that includes links to a lot of the records in the site to help improve navigation.

I originally tried putting the cache statement in the layout file but then it was rendering the layout twice.

I recently added a jQuery hack to remove the duplicate html so that it kinda “works” for now, but I would rather get it working properly. I don’t want to go to the trouble of installing some complicated caching system such as Redis, that requires me to run another server program. That would be overkill for the task. There must be something in rails that is well suited to caching parts of layouts.

Should I try something completely different or is this a bug in rails? If it is a bug then is there a workaround I can use?

Answer 1

I figured it out. Instead of caching the partial in the view, I created a helper method that returns the rendered partial.

#Returns a menu for the application layout
def menu
  Rails.cache.fetch('menu') { render :partial => 'all/menu' }
end

Then all I needed in the layout is this line
<% menu %>