Ruby Daemons

Ruby Daemons
Creston Jamison
RubyTree Software, Inc.

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!

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Ruby Daemons

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