Fallen

A simpler daemon library for Ruby processes.

Usage

require "fallen"

module Azazel
  extend Fallen
  
  def self.run
    while running?
      puts "Time is on my side... Yes it is..."
      sleep 666
    end
  end
end

Azazel.start!

This will print Time is on my side... Yes it is.. every 666 seconds on STDOUT. You can stop the daemon by pressing CTRL+c.

Callbacks

Fallen includes four callback methods that are executed on starting and stopping the daemon. These are:

before_start
after_start
before_stop
after_stop

Override them in your script to add the desired functionality, like so:

require "fallen"

module Azazel
  extend Fallen
  
  def self.run
    while running?
      # Do something
    end
  end
  
  def self.before_start
    puts "I'm just getting started!"
  end
  
  def self.before_stop
    puts "I'm about to stop. Bye!"
  end
end

Control your daemon

Fallen accepts the following methods:

daemonize!: detaches the process and keeps running it in the background;
chdir!: changes the current working directory of the process (useful for log and PID files);
pid_file: allows to indicate a file path where the daemon PID will be stored; could be either an absolute or a relative path to the current working directory (see chdir!);
stdout, stderr & stdin: redirect the process STDOUT, STDERR and STDIN to either an absolute or relative file path; note that when a process is daemonized by default all these streams are redirected to /dev/null.

For example, the previous example could have the following lines before Azazel.start! to store the PID and log to a file:

Azazel.pid_file "/var/run/azazel.pid"
Azazel.stdout "/var/log/azazel.log"
Azazel.daemonize!
Azazel.start!

CLI support

Fallen supports command line parameters, by default using the clap gem. In order to enable command line support you need to do the following:

require "fallen"
require "fallen/cli"

module Azazel
  extend Fallen
  extend Fallen::CLI
  
  # ...
  
  def self.usage
    puts "..." # Your usage message
    # Default Fallen usage options
    puts fallen_usage
  end
end

case Clap.run(ARGV, Azazel.cli).first
when "start"
  Azazel.start!
when "stop"
  Azazel.stop!
else
  Azazel.usage
end

Azazel.usage will print the following:

Fallen introduced command line arguments:

  -D    Daemonize this process
  -C    Change directory.
  -P    Path to PID file. Only used in daemonized process.
  -out  Path to redirect STDOUT.
  -err  Path to redirect STDERR.
  -in   Path to redirect STDIN.

License

See the UNLICENSE file included with this gem distribution.

lenn4rd / fallen