Rails cache expire

Question

I have a rails application, in that I am using simple rails cache. My testing is as follows:

Rails.cache.write('temp',Date.today,:expires_in => 60.seconds)

I can read it through Rails.cache.read('temp') and Rails.cache.fetch('temp').

The problem is it doesn't expire. It will still be alive after 60 seconds. Can any one tell me what is missing here.

FYI: I have declared in my development.rb as follows :

config.action_controller.perform_caching = true

config.cache_store = :memory_store

Is there anything I missed out? I want to expires my cache.

Answer 1

After some search, I have found one possible reason why the cache is not cleaned after 60 seconds.

1. You call Rails.cache.write which is documented here.
2. It calls write_entry(namespaced_key(name, options), entry, options), where your option :expires_in is one part of the options argument.

3. The implementation of write_entry has the following condition:

   if expires_in > 0 && !options[:raw]
       # Set the memcache expire a few minutes in the future to support race condition ttls on read
       expires_in += 5.minutes
   end
   

So there are 5 minutes added to your 60 seconds. 2 possible solutions:

• Just live with it :-)
• Try to include the option :raw => true, perhaps this will skip the condition, so that your expiry works as suspected.