Does phusion passenger use forking, and if so, where to set after_fork config?

Question

Does phusion passenger use forking? If so, where should I set an after_fork configuration, as recommended by Heroku for unicorn (re: Setting up PostGIS with Rails)?

From Heroku's docs:

Additionally, if unicorn or any other process forking code is used where the connection is re-established, make sure to override the adapter to postgis as well. For example:

# unicorn.rb
after_fork do |server, worker|
  if defined?(ActiveRecord::Base)
    config = Rails.application.config.database_configuration[Rails.env]
    config['adapter'] = 'postgis'
    ActiveRecord::Base.establish_connection(config)
  end
end

Answer 1

Yes, Phusion Passenger does forking, almost exactly like how Unicorn does it. Unicorn's default behavior (preload_app off) is the same as Phusion Passenger's "direct spawning" (not default in Phusion Passenger). Unicorn's preload_app on is the same as Phusion Passenger's "smart spawning" (default in Phusion Passenger). Sources:

• passenger_spawn_method documentation
• Appendix C: Spawning methods explained

The latter also teaches you how to install an after-fork hook.

Answer 2

Phusion Passenger is primarily multi-process; the Enterprise version can do both multi-process and multi-threaded.

• Ruby on Rails Server options
• http://blog.phusion.nl/2013/03/12/tuning-phusion-passengers-concurrency-settings/

I don't know if an after_fork type thing is needed with Passenger, because it's not Ruby doing the forking of the process, but I'm not 100% sure there.