Question

I have an initializer in my config directory, which is something like this:

ActiveSupport::Notifications.subscribe "handle_translation_event" do |name, start, finish, id, payload|
  puts "Called"
end

I have a Rails development server running ( rails s ), and I start in parallel a rails console ( rails c ). Imagine that in the rails console, I write:

ActiveSupport::Notifications.instrument("handle_translation_event")

I cannot see this reflected in the server logs. Is it possible to trigger an event from the console, and have it affect the server? My guess is no.

Answer 1

ActiveSupport::Notifications uses ActiveSupport::Notifications::Fanout class as notifier to notify the subscribers.

This notifier uses simple instance variables to store the subscribers.

You can create your own implementation (with a database backed solution) and you can set the actual notifier to your implementation by setting the notifier attribute of ActiveSupport::Notifications.

ActiveSupport::Notifications.notifier = my_implementation

I could imagine a simple Redis backed implementation of it, because it has a publish/subscribe feature. But if you don’t have Redis as a dependency, you can also do it in SQL.