Learn how to use daemons with your ruby based application like Ruby on Rails. See how it compares to other queueing systems like Queue Classic, Sidekiq, or Delayed Job.

1. Ruby Daemons
Creston Jamison
RubyTree Software, Inc.

3. GAMEhud
 HTTPAPI accepts event and player based
data from game clients.
 Incoming data needs to be distributed
between 10-20 tables.
 Don’t want to do that in the request.
 Need to do background processing!

4. 1. Reliability
2. Speed

5. Background Processing Options
 Delayed Job
 Beanstalkd
 Resque
 Sidekiq
 Queue Classic
 Daemons

6. Delayed Job
 Uses rake
 Uses full rails environment
 Best for long running and infrequent jobs

7. Beanstalkd
 Fast queue
 Does not poll
 Good for raw speed
 Authentication and queue management ?

8. Resque
 Redis based queue system
 Requires Redis
 Comes with an admin interface
 Uses polling

9. Sidekiq
 Redis based queue system
 Requires Redis
 Comes with an admin interface
 Uses polling
 Uses threads
 Code needs to be thread safe

10. Queue Classic
 Postgres based queue system
 Requires postgresql
 Avoids separate queue process
 Can avoid polling

11. Queue vs. Worker

12. Daemons
 Converts a script into a daemon
 Not a queue system
 A way to create a worker process

13. What is a daemon?
 A computer program that runs as a
background process
 Daemon processes typically end in ‘d’
 For example: sshd

14. Setting up a daemon
 Install daemons gem
 Create a control file
event_worker_control.rb
 Create a loop in the script called by the control file
event_worker.rb

15. Create a control file
require 'rubygems'
require 'bundler/setup'
require 'daemons'
Daemons.run('lib/daemons/event_worker.rb')

16. Loop in your script
$: << File.expand_path(".", File.dirname(__FILE__))
require ‘event_processor'
event_processor = EventProcessor.new
loop do
event_processor.process
sleep(5)
end

17. Control your daemon
 ruby daemon-name_control.rb start
 ruby daemon-name_control.rb restart
 ruby daemon-name_control.rb stop
 ruby lib/daemons/event_worker_control.rb
start -- production
 PID file

18. Capistrano
before 'deploy:update_code', 'deploy:stop_workers'
desc "Stop the worker processes“
task :stop_workers, :roles => :app do
run "cd #{current_path};
ruby lib/daemons/event_worker_control.rb
stop -- production“
end

19. Gotchas
 Need rock solid error handling
 Otherwise your process dies
 Need a way to skip over errors and come back
to them

20. Extra Credit
jstorimer.com/2012/04/19/daemon-processes-in-ruby.html
labs.headlondon.com/2010/07/skinny-daemons/

21. Questions?
Creston Jamison
@crestonjamison
creston.jamison@rubytreesoftware.com