Custom Daemon with Rails 3 - ruby-on-rails

Question

I'm trying to create a custom daemon that loads up the Rails environment.
My environment is as follows:
ruby-1.9.2-p180
rails 3.0.5
I did the following:
-Installed the daemons gem
-Installed daemon_generator plugin found here:
https://github.com/dougal/daemon_generator
-Generated a daemon: rails generate daemon listener
All this worked fine. When I run the daemon, it works.
However, as soon as I try to access an active record object like trying to retrieve a user, it blows up.
*** below you find the most recent exception thrown, this will be likely (but not certainly) the exception that made the application exit abnormally ***
#<NameError: method `recognize' not defined in Rack::Mount::RouteSet>
*** below you find all exception objects found in memory, some of them may have been thrown in your application, others may just be in memory because they are standard exceptions ***
#<NoMemoryError: failed to allocate memory>
#<SystemStackError: stack level too deep>
#<fatal: exception reentered>
#<NoMethodError: undefined method `eq' for nil:NilClass>
#<NameError: method `recognize' not defined in Rack::Mount::RouteSet>
Any thoughts on how to create a Daemon that loads up Rails 3.0.5?

Answer 1

I prefer to roll my own rails daemon controllers. Here is a simple example that works for most cases:
script/daemon
#!/usr/bin/env ruby
require 'rubygems'
require 'daemons'
ENV["APP_ROOT"] ||= File.expand_path("#{File.dirname(__FILE__)}/..")
ENV["RAILS_ENV_PATH"] ||= "#{ENV["APP_ROOT"]}/config/environment.rb"
script = "#{ENV["APP_ROOT"]}/daemons/#{ARGV[1]}"
Daemons.run(script, dir_mode: :normal, dir: "#{ENV["APP_ROOT"]}/tmp/pids")
daemons/your_daemon_script.rb
require ENV["RAILS_ENV_PATH"]
loop {
... your code ...
}
You can control your deamons by using the following commands:
script/daemon run your_daemon_script.rb
script/daemon start your_daemon_script.rb
script/daemon stop your_daemon_script.rb
This enables me to easily add new daemons and I can easily load rails in each script if necessary.

Answer 2

I had a lot of problems trying get daemon_generator working. I got my daemon working by skipping the daemon_generator all together and just using the daemons gem (v1.1.3).
in urserver_control.rb (in root ruby app directory):
#!/usr/bin/env ruby
require 'rubygems'
require 'daemons'
require 'TweetMsg'
Daemons.run('urserver.rb')
in urserver.rb:
#!/usr/bin/env ruby
require File.expand_path(File.join(File.dirname(__FILE__), 'config', 'environmen
t'))
require "rubygems"
--- insert your code here ---
You can test by running your server directly ruby urserver.rb or ruby urserver_controller run
And then once that is working starting and stopping the controllerruby urserver_control.rb {start | stop | run }

Answer 3

Looking at the code in https://github.com/dougal/daemon_generator/blob/master/lib/generators/daemon/templates/script.rb it appears they load things in the wrong order...
Looking at my delayed_job daemon script and config.ru they load config/environment.rb (which in turn loads application.rb and initializes the app)
So a possible fix would be to edit the generated script and make it only require 'config/environment.rb'
I tried this:
#!/usr/bin/env ruby
# You might want to change this
ENV["RAILS_ENV"] ||= "development"
require File.dirname(__FILE__) + "/../config/environment"
$running = true
Signal.trap("TERM") do
$running = false
end
while($running) do
# Replace this with your code
Rails.logger.auto_flushing = true
o = Order.last
Rails.logger.info "The latest order is #{o.id}"
sleep 10
end
and it yielded no errors... (Tried both Rails 3.0.3 and 3.0.5)

Answer 4

I had problems running daemon as is on my staging server (Rails 3.0.7, ruby 1.8.7, passenger 3.0.0). Neither
require File.dirname(FILE) + "/../../config/application"
Rails.application.require_environment!
nor
require File.dirname(FILE) + "/../config/environment"
Worked.
I fixed it by re-installing the standard config.ru in rails root (which I had de-installed to integrate w passenger... not sure now how I will get daemons & passenger to work together now ...)