cache_keys.rb

# Redis::Objects is the only requirement for this solution
require 'redis/objects'

module Redis::CacheKeys
  class ReservedKey < Exception; end

  def self.included(base)
    base.class_eval do
      include Redis::Objects unless base.included_modules.include?(Redis::Objects)

      set "cache_keys"
    end
  end

  def cache_compound_key(key)
    raise ReservedKey, "#{key} is a reserved key." if key == 'cache_keys'

    "#{self.class.table_name}_#{self.id}_#{key}"
  end

  def cache_key(key)
    cache_compound_key(key).tap do |compound_key|
      self.cache_keys << compound_key
    end
  end

  def cache_expire(key = nil)
    # When key is nil, expire all cache keys
    if key.nil?
      self.cache_keys.each do |compound_key|
        ActionController::Base.new.expire_fragment(compound_key)
      end
    else
      cache_compound_key(key).tap do |compound_key|
        ActionController::Base.new.expire_fragment(compound_key)
      end
    end
  end
end

Usage:

some_model = Model.find(123456)

Slow view to cache

cache(some_model.cache_key('slow_area')) do

...

Later, we want to only expire this 'slow_area'

some_model.cache_expire('slow_area')

Even later, we want to expire everything for this model

some_model.cache_expire