How to Expire a View Cached Fragment from Console

How do I expire a view cached fragment from console?

Cache fragment entries are created with a slightly different key than what you access with Rails.cache.

Use expire_fragment instead (you can send it to a controller): http://api.rubyonrails.org/classes/ActionController/Caching/Fragments.html#M000438

Rails 4 Fragment Cache Entire Page. How to Expire Cache In Model

I believe your issue is the digest, so if you change your cache to this it should work:

<% cache 'main-page', skip_digest: true do %>
  # html here
<% end %>

If you want to use this kind of style, where the cache doesn't expire and relies on detecting model changes to invalidate, you may want to consider using an Observer or Sweeper, which were removed from Rails 4, but are useful for this pattern:

https://github.com/rails/rails-observers

Not the answer you are looking for perhaps, but another way:

Make the cache key based on the max updated_at from the Post model.

Whenever any post changes, the cache key will automatically miss and go retrieve the latest posts to re-cache that part of the view.

module HomeHelper
  def cache_key_for_posts
    count          = Post.count
    max_updated_at = Post.maximum(:updated_at).try(:utc).try(:to_s, :number)
    "posts/all-#{count}-#{max_updated_at}"
  end
end

And then in your view:

<% cache cache_key_for_posts, skip_digest: true do %>
  # html here
<% end %>

Manually Clear Fragment Cache in Rails

I ended up manually clearing the entire cache by going into the rails console and using the command:

Rails.cache.clear

Rails 4.0 expire_fragment/cache expiration not working

I believe the issue is that when you cache the fragment in your view, a cache digest is being added to the cache key (views/all_available_releases/41cb0a928326986f35f41c52bb3d8352), but expire_fragment is not using the digest (views/all_available_releases).

If you add skip_digest: true to the cache call in the view it should prevent the digest from being used.

<% cache "all_available_releases", skip_digest: true do %>
 <% @releases.each do |release| %>
  <% cache(release) do %>
   <html code with>
   <%ruby code @release.name blah blah blah%>
  <%end%>
 <%end%>
<%end%>

Cache digests are only intended to be used with automatic cache expiration. If you need to manually expire cache keys then you can't use cache digests.

Rails - fragment cache not expiring

You might try this:

   cache("news") do    
     %h2 News
     - etc
   end

and...

def expire_home_cache
  puts "expire_home_cache"
  expire_fragment("news") 
end

...or try this ...

 - cache({:key=>"news"}) do    
   %h2 News
   - etc

I am thinking the issue may be that ruby or rails is having a hard time determining what the key is exactly and so the cache method and expire_fragment are generating two different cache keys.

How to get the proper key to use expire_fragment?

I'm not sure if this is by design, or whether there is a bug in Rails. But what is happening is the suffix /dca9add42d461d4c76103c08d12a6571 that's added to the end of the cache key when I use the cache command in my views, is a digest, which you can skip by calling cache like so:

<% cache("my-key", { :skip_digest: true }) %>
    html
<% end %>

That way the suffix (digest) gets left off the key.

Now where I think a possible bug (?) is coming in, is that the expire_fragment command doesn't add the digest to the end of the key - so I never actually end up expiring my fragments.

So my answer for now - is to use :skip_digest: true if I want to manually expire them.

Rails fragment caching strategy

Action caching is also technically type of fragment caching which wraps your fragment. So your fragment might expire but this will not be visible untill the action cache expires.

So if want your fragment to expire you need to expire the action as well. But the fragment caching is not without purpose. If the action expires, the cached fragment will be used.