需要缓存5分钟的Rails片段

Question

These are some lines I have in Rails:

@quickbar_posts = []
SETTINGS[:news_groups].each do |group_short_name|
  @quickbar_posts << quickbar_posts(group_short_name)
end

What I would like is that variable @quickbar_posts to be cached in memory for 5 minutes OR for the final output of the function quickbar_posts (after it has exited the for-loop) to be saved locally in the filesystem for 5 minutes.

My problem is that every time this is run, it's highly inefficient for this to be fetched every time, so I just want it saved for 5 minutes, then fetched again, invalidating the previously cached item if the age of the cached item is > 5 minutes.

In addition, adding or changing gems is not possible - since this code is running in production and for reasons that can't be explained here, nothing else can be changed in production.

Answer 1

ActiveSupport part of Rails allows to use cache.

You should verify that cache is enabled so in config/enviroments/production.rb you should set the following flag:

config.action_controller.perform_caching = true

To cache @quickbar_posts for 5 minutes, you can use the following code:

@quickbar_posts = Rails.cache.fetch("quickbar_posts", expires_in: 5.minutes) do
    SETTINGS[:news_groups].map{|group_short_name| quickbar_posts(group_short_name)}
end

Ruby 1.8.7 syntax:

@quickbar_posts = Rails.cache.fetch("quickbar_posts", :expires_in => 5.minutes) do
    SETTINGS[:news_groups].map{|group_short_name| quickbar_posts(group_short_name)}
end

You can use different cache stores, to set the one you want, you can do it in config/application.rb on in config/environments/your_environment.rb (production/test/deploy)

To use ActiveSupport::Cache::MemoryStore :

config.cache_store = :memory_store

To use ActiveSupport::Cache::FileStore :

config.cache_store = :file_store, "/path/to/cache/directory"