How can I list the keys in the in-memory cache store on Ruby on Rails?

Question

I am using Rails 3.

How can I list the keys in the in-memory cache store on Ruby on Rails?

Answer 1

Rails.cache.instance_variable_get(:@data).keys 

Answer 2

ActiveSupport::Cache::MemoryStore doesn't provide a way to access the store's keys directly (and neither does its parent class ActiveSupport::Cache::Store).

Internally MemoryStore keeps everything in a Hash called @data, however, so you could monkey-patch or subclass it to get the keys, e.g.:

class InspectableMemoryStore < ActiveSupport::Cache::MemoryStore   def keys     @data.keys   end end  ActionController::Base.cache_store = InspectableMemoryStore.new  Rails.cache.keys # => [ "foo", ... ] 

This comes with the usual caveat, however: MemoryStore's internal implementation may change at any time and @data may disappear or be changed to something that doesn't respond_to? :keys. A smarter implementation might be to override the write and delete methods (since, as part of the public API, they're unlikely to change unexpectedly) to keep your own list of keys, e.g.:

class InspectableMemoryStore < ActiveSupport::Cache::MemoryStore   def write *args     super      @inspectable_keys[ args[0] ] = true   end    def delete *args     super      @inspectable_keys.delete args[0]   end    def keys     @inspectable_keys.keys   end end 

This is a very naive implementation, and of course keeping the keys in an additional structure takes up some memory, but you get the gist.