Setting the cache_store in an initializer

After some research, a probable explanation is that the initialize_cache initializer is run way before the rails/initializers are. So if it's not defined earlier in the execution chain then the cache store wont be set. You have to configure it earlier in the chain, like in application.rb or environments/production.rb

My solution was to move the APP_CONFIG loading before the app gets configured like this:

APP_CONFIG = YAML.load_file(File.expand_path('../config.yml', __FILE__))[Rails.env]

and then in the same file:

config.cache_store = :redis_store, APP_CONFIG['redis']

Another option was to put the cache_store in a before_configuration block, something like this:

config.before_configuration do  APP_CONFIG = YAML.load_file(File.expand_path('../config.yml', __FILE__))[Rails.env]  config.cache_store = :redis_store, APP_CONFIG['redis']end

The config/initializers are run after the Rails.cache is initialized, but after config/application.rb and config/environments.

Configuration in config/application.rb or environments

Thus, one solution would be to configure the cache in config/application.rb or config/environments/*.rb.

Configuration in config/initializers/cache.rb

If the cache should be configured in an initializer intentionally, this can be done by setting Rails.cache manually after the configuration:

# config/initializers/cache.rbRails.application.config.cache_store = :redis_store, APP_CONFIG['redis']# Make sure to add this line (http://stackoverflow.com/a/38619281/2066546):Rails.cache = ActiveSupport::Cache.lookup_store(Rails.application.config.cache_store)

Add a spec

In order to make sure it worked, add a spec like this:

# spec/features/smoke_spec.rbrequire 'spec_helper'feature "Smoke test" do  scenario "Testing the rails cache" do    Rails.cache.write "foo", "bar"    expect(Rails.cache.read("foo")).to eq "bar"    expect(Rails.cache).to be_kind_of ActiveSupport::Cache::RedisStore  endend

Further information

• Rails.cache is set here during the application bootstrap: https://github.com/rails/rails/blob/5-0-stable/railties/lib/rails/application/bootstrap.rb#L62L70. The redis store does not respond to :middleware. Thus, we can leave out the additional lines.
• See also: https://github.com/rails/rails/issues/10908#issuecomment-19281765
• http://guides.rubyonrails.org/caching_with_rails.html#cache-stores

I tried the following and it works out.

MyApp::Application.config.cache_store = :redis_storeself.class.send :remove_const, :RAILS_CACHE if self.class.const_defined? :RAILS_CACHERAILS_CACHE = ActiveSupport::Cache.lookup_store(MyApp::Application.config.cache_store)