Manually Generating Rails Cache Key

Question

I'm trying to use isolated workers to build and manipulate my cache. I would like to keep these workers as lean as possible. (don't use rails)

I'm having difficulty forging rails generated cache keys

In my view I have this:

cache ["comments", @ama]

I'm trying to replicate the key that it produces with the following:

updated_at = Time.parse(row['updated_at'])
timestamp = updated_at.utc.strftime('%Y%m%d%H%M%S')
cache_key = "views/comments/amas/#{row['id']}-#{timestamp}"

Which will produce:

views/comments/amas/432-20121227010114

The cache from that key is blank.

Either I'm not formatting my key correctly, or the cache is missing. I'm 95% confident the cache i'm seeking is there.

(I'm able to push cache with a key such as 'test', and then get it back. So I know the caching is working)

Helpful References:

• http://apidock.com/rails/ActiveRecord/Base/cache_key
• http://apidock.com/rails/ActiveSupport/CoreExtensions/Time/Conversions

Helpful Information:

• The cache server isn't local, and yes I'm pointing to it.
• Even if the key didn't exist, When I load the page in production the key & cache would be built on the spot. Which I have tried.
• using Rails 4.0.0

Answer 1

The most efficient way to implement low-level caching is using the Rails.cache.fetch method. It will read a value from the cache if it available; otherwise it will execute a block passed to it and return the result:

You can manually set the cache key from rails console(by typing 'rails c' in command prompt)

>> Rails.cache.fetch('answer')
==> "nil"
>> Rails.cache.fetch('answer') {1 + 1}
==> 2
Rails.cache.fetch('answer')
==> 2

Consider the following example. An application has a Product model with a class method returning all out of stock items, and an instance method that looks up the product’s price on a competing website. The data returned by these methods would be perfect for low-level caching:

# product.rb

def Product.out_of_stock
  Rails.cache.fetch("out_of_stock_products", :expires_in => 5.minutes) do
    Product.all.joins(:inventory).conditions.where("inventory.quantity = 0")
  end
end

def competing_price
  Rails.cache.fetch("/product/#{id}-#{updated_at}/comp_price", :expires_in => 12.hours) do
    Competitor::API.find_price(id)
  end
end

I think it will be helpful for you.

Thanks.

Answer 2

template cache keys look like this:

views/projects/123-20120806214154/7a1156131a6928cb0026877f8b749ac9
       ^class   ^id ^updated_at    ^template tree digest

Reference: http://api.rubyonrails.org/classes/ActionView/Helpers/CacheHelper.html#method-i-cache