looper

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Looper is a dead simple Ruby module for daemonizing your code, meant for use with Rails' script/runner. No forking involved, no detaching, simply running a nice healthy loop, but allowing your code to bail out of it, and making it responsive to signals.

You implement a class like "DoSomething" that checks for new message objects and then does something to them. This class will include @Looper@ in order to easily loop, respond to shutdown signals, and it can then be run via script/runner as a daemon.

The loop handles sleeping between runs, and will catch any unhandled exceptions that bubble up and keep on truckin'. Thus, if you want to exit on a particular exception, you've got to rescue it in your code and set @@run@ to @false@.

Here's an example usage:

require 'looper'

class DoSomething
  include Looper
  
  attr_accessor :run
  
  def initialize(config)
    @run = true
    # do config stuff, etc...
    @sleep = config[:sleep].nil? ? 60 : config[:sleep]
  end # initialize
  
  def run
    loopme(@sleep) do
      begin
        # this is where the meat of your code goes...
        messages = twitter.direct_messages({:since => since.strftime("%a, %d %b %Y %H:%M:%S %Z")})
      rescue Twitter::EpicFailure => e
        puts "bailing out, dude!"
        # set run to false to put the kabosh on the next run
        @run = false
      end
    end
  end
end

# and here's how we kick it off:
DoSomething.new( { :sleep => 10 } ).run

Now we can just kick that off any way we like and background the process, but we tend to use it with script/runner in our Rails environments to have access to our models and such. It boils down to:

@$ nohup script/runner -e RAILS_ENV /path/to/DoSomething.rb@

And then looking up the PID by matching on /path/to/DoSomething.rb via grep and use kill to send the term signal.