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Daemons Version 1.0.11

(See Releases for release-specific information)

What is Daemons?

Daemons provides an easy way to wrap existing ruby scripts (for example a self-written server) to be run as a daemon and to be controlled by simple start/stop/restart commands.

If you want, you can also use daemons to run blocks of ruby code in a daemon process and to control these processes from the main application.

Besides this basic functionality, daemons offers many advanced features like exception backtracing and logging (in case your ruby script crashes) and monitoring and automatic restarting of your processes if they crash.

Daemons includes the <tt>daemonize.rb</tt> script written by Travis Whitton to do the daemonization process.

Basic Usage

You can use Daemons in four differet ways:

1. Create wrapper scripts for your server scripts or applications

Layout: suppose you have your self-written server <tt>myserver.rb</tt>:

# this is myserver.rb
# it does nothing really useful at the moment

loop do
  sleep(5)
end

To use <tt>myserver.rb</tt> in a production environment, you need to be able to run <tt>myserver.rb</tt> in the background (this means detach it from the console, fork it in the background, release all directories and file descriptors).

Just create <tt>myserver_control.rb</tt> like this:

# this is myserver_control.rb

require 'rubygems'        # if you use RubyGems
require 'daemons'

Daemons.run('myserver.rb')

And use it like this from the console:

$ ruby myserver_control.rb start
    (myserver.rb is now running in the background)
$ ruby myserver_control.rb restart
    (...)
$ ruby myserver_control.rb stop

For testing purposes you can even run <tt>myserver.rb</tt> without forking in the background:

$ ruby myserver_control.rb run

An additional nice feature of Daemons is that you can pass additional arguments to the script that should be daemonized by seperating them by two hyphens:

$ ruby myserver_control.rb start -- --file=anyfile --a_switch another_argument

2. Create wrapper scripts that include your server procs

Layout: suppose you have some code you want to run in the background and control that background process from a script:

# this is your code
# it does nothing really useful at the moment

loop do
  sleep(5)
end

To run this code as a daemon create <tt>myproc_control.rb</tt> like this and include your code:

# this is myproc_control.rb

require 'rubygems'        # if you use RubyGems
require 'daemons'

Daemons.run_proc('myproc.rb') do
  loop do
    sleep(5)
  end
end

And use it like this from the console:

$ ruby myproc_control.rb start
    (myproc.rb is now running in the background)
$ ruby myproc_control.rb restart
    (...)
$ ruby myproc_control.rb stop

For testing purposes you can even run <tt>myproc.rb</tt> without forking in the background:

$ ruby myproc_control.rb run

3. Control a bunch of daemons from another application

Layout: you have an application <tt>my_app.rb</tt> that wants to run a bunch of server tasks as daemon processes.

# this is my_app.rb

require 'rubygems'        # if you use RubyGems
require 'daemons'

task1 = Daemons.call(:multiple => true) do
  # first server task

  loop {
    conn = accept_conn()
    serve(conn)
  }
end

task2 = Daemons.call do
  # second server task
  
  loop {
    something_different()
  }
end

# the parent process continues to run

# we can even control our tasks, for example stop them
task1.stop
task2.stop
  
exit

4. Daemonize the currently running process

Layout: you have an application <tt>my_daemon.rb</tt> that wants to run as a daemon (but without the ability to be controlled by daemons via start/stop commands)

# this is my_daemons.rb

require 'rubygems'        # if you use RubyGems
require 'daemons'

# Initialize the app while we're not a daemon
init()

# Become a daemon
Daemons.daemonize

# The server loop
loop {
  conn = accept_conn()
  serve(conn)
}

For further documentation, refer to the module documentation of Daemons.

Download and Installation

Download: just go to http://rubyforge.org/projects/daemons/

Installation with RubyGems:

$ su
# gem install daemons

Installation without RubyGems:

$ tar xfz daemons-x.x.x.tar.gz
$ cd daemons-x.x.x
$ su
# ruby setup.rb

Documentation

For further documentation, refer to the module documentation of Daemons (click on Daemons).

The RDoc documentation is also online at http://daemons.rubyforge.org

Author

Written in 2005-2008 by Thomas Uehlinger mailto:th.uehlinger@gmx.ch.

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

This license does not apply to daemonize.rb, which is was written by Travis Whitton und published under the following license:

The Daemonize extension module is copywrited free software by Travis Whitton whitton@atlantic.net. You can redistribute it under the terms specified in the COPYING file of the Ruby distribution.

Feedback and other resources

At http://rubyforge.org/projects/daemons.