Is Rails.cache.fetch method atomic?

Question

Specifically, if the key does not exist in the cache, I want to add the key-value pair to the cache. Can this be done atomically using Rails.cache.fetch?

Thanks!

Answer 1

You have to write with the :unless_exist option:

Rails.cache.write(k, v, :unless_exist => true)

The method will return true only when the key didn't exist. Otherwise, the method returns false:

if Rails.cache.write(k, v, :unless_exist => true)
  # do something only when the key wasn't there
end