Daemonizer: Simple framework for creating daemons with Ruby

Homepage: http://daemonizer.org Git: http://github.com/glebpom/daemonizer Author: Gleb Pomykalov Copyright: 2010 License: MIT License Status: alpha

Synopsis

Daemonizer is a simple ruby framework to create custom daemons. It is fully compatible with EventMachine, Rails and any other Ruby frameworks.

Feature List

1. Daemonfile (similar to Gemfile, Rakefile) as a configuration file. It is possible to describe different worker pools there.

2. Monitoring: If child is found dead it will be immediately restored

3. Logging

4. Statistics: Daemonizer collects worker statistics and let you kill workers if some statistics exceeds regular values.

Installing

To install Daemonizer, use the following command:

$ gem install daemonizer

(Add sudo if you're installing under a POSIX system as root)

Usage

Demfile example:

workers 2
poll_period 5

pool :daemonizer do
  workers 4
  log_file "log/daemonizer.log" #relative to Demfile

  prepare do |block|
    block.call
  end

  start do |worker_id, workers_count|
    logger.info "Started #{worker_id} from #{workers_count}"

    exit = false

    stop = proc {
      exit = true
    }

    trap('TERM', stop)
    trap('INT', stop)
    trap('EXIT', stop)

    loop do
      break if exit
      logger.info "Ping #{worker_id}"
      sleep 10
    end

    true
  end
end

settings_group do
  before_start do |worker_id, workers_count|
    #reconnect to db, etc.
  end

  #simple string option
  set_option :author, "Gleb Pomykalov"

  pool :new_daemonizer do
    on_poll do |pool|
      pool.stats.where(:private_dirty_rss).last_probes_by_count(8).mean.is_higher_then(150_000) do |stat|
        Daemonizer.logger.info "Memory limit exceeded for #{stat}. Gracefully stopping"
        worker = pool.find_worker_by_name(stat)
        worker.stop if worker
      end
    end
    workers 4
    log_file "log/daemonizer.log" #relative to Demfile

    handler MyBackgroundSolution::DaemonizerHandler

    not_cow_friendly #disable Copy-On-Write friendly (enabled by default)

    #automatically-parsed option by daemonizer
    set_option :queue do |worker_id, worker_count|
      "queue_#{worker_id}"
    end

    #lambda-option (transparent for daemonizer, fully processed by handler)
    set_option :on_error, lambda { |object| object.logger.fatal "epic fail"}
  end


  pool :new_daemonizer2 do
    workers 4
    log_file "log/daemonizer2.log" #relative to Demfile

    handler MyBackgroundSolution::DaemonizerHandler

    not_cow_friendly #disable Copy-On-Write friendly (enabled by default)

    #automatically-parsed option by daemonizer
    set_option :queue do |worker_id, worker_count|
      "another_queue_#{worker_id}"
    end

    after_prepare do |logger|
      require 'something'
    end

    #lambda-option (transparent for daemonizer, fully processed by handler)
    set_option :on_error, lambda { |object| object.logger.fatal "epic fail"}
  end
end

Handler example

module MyBackgroundSolution
  class DaemonizerHandler < Daemonizer::Handler
    def preparee(starter, &block)
      require File.join(Daemonizer.root, '/config/environment') #Require rails
      require 'my_background_solution/worker' #Require our code
      super #now we are ready to fork
    end

    def start
      #we are in worker process
      logger.info "Starting cycle. We are number #{worker_id} from #{workers_count}"
      logger.info "Options - #{option(:queue)}" #We can get option :queue, which is set with set_option in pool configuration
      worker = Worker.new
      worker.run
      logger.info "Ending cycle"
    end
  end
end

Who are the authors

This gem has been created in qik.com for our internal use and then the sources were opened for other people to use. All the code in this package has been developed by Gleb Pomykalov. As for the first versions, it was mostly based on http://github.com/kovyrin/loops code written by Alexey Kovyrin. Now most of it is heavily refactored. MemoryStats is taken from Phusion Passenger.The gem is released under the MIT license. For more details, see the LICENSE file.