Parent

Daemons::PidFile

What is a Pid-File?

A Pid-File is a file containing the process identification number (pid) that is stored in a well-defined location of the filesystem thus allowing other programs to find out the pid of a running script.

Daemons needs the pid of the scripts that are currently running in the background to send them so called signals. Daemons uses the TERM signal to tell the script to exit when you issue a stop command.

How does a Pid-File look like?

Pid-Files generated by Daemons have to following format:

<scriptname>.rb<number>.pid

(Note that <number> is omitted if only one instance of the script can run at any time)

Each file just contains one line with the pid as string (for example 6432).

Where are the Pid-Files stored?

Daemons is configurable to store the Pid-Files relative to three different locations:

  1. in a directory relative to the directory where the script (the one that is supposed to run as a daemon) resides (:script option for :dir_mode)

  2. in a directory given by :dir (:normal option for :dir_mode)

  3. in the preconfigured directory /var/run (:system option for :dir_mode)

Attributes

dir[R]
multiple[R]
number[R]
progname[R]

Public Class Methods

existing(path) click to toggle source
# File lib/daemons/pidfile.rb, line 55
def PidFile.existing(path)
  new_instance = PidFile.allocate
  
  new_instance.instance_variable_set(:@path, path)
  
  def new_instance.filename
    return @path
  end
  
  return new_instance
end
find_files(dir, progname, delete = false) click to toggle source
# File lib/daemons/pidfile.rb, line 36
def PidFile.find_files(dir, progname, delete = false)
  files = Dir[File.join(dir, "#{progname}*.pid")]
  
  files.delete_if {|f| not (File.file?(f) and File.readable?(f))}
  if delete 
    files.delete_if do |f|
      pid = File.open(f) {|h| h.read}.to_i
      rsl =  ! Pid.running?(pid)
      if rsl
        puts "pid-file for killed process #{pid} found (#{f}), deleting."
        begin; File.unlink(f); rescue ::Exception; end
      end
      rsl
    end
  end

  return files
end
new(dir, progname, multiple = false) click to toggle source
# File lib/daemons/pidfile.rb, line 67
def initialize(dir, progname, multiple = false)
  @dir = File.expand_path(dir)
  @progname = progname
  @multiple = multiple
  @number = nil
  @number = 0 if multiple
  
  if multiple
    while File.exist?(filename) and @number < 1024
      @number += 1
    end
    
    if @number == 1024
      raise RuntimeException('cannot run more than 1024 instances of the application')
    end
  end
end

Public Instance Methods

cleanup() click to toggle source
# File lib/daemons/pidfile.rb, line 100
def cleanup
  File.delete(filename) if pid == Process.pid
end
exist?() click to toggle source
# File lib/daemons/pidfile.rb, line 89
def exist?
  File.exist? filename
end
filename() click to toggle source
# File lib/daemons/pidfile.rb, line 85
def filename
  File.join(@dir, "#{@progname}#{ @number or '' }.pid")
end
pid() click to toggle source
# File lib/daemons/pidfile.rb, line 104
def pid
  begin
    File.open(filename) {|f|
      return f.gets.to_i
    }
  rescue ::Exception
    return nil
  end
end
pid=(p) click to toggle source
# File lib/daemons/pidfile.rb, line 93
def pid=(p)
  File.open(filename, 'w') {|f|
    f.chmod(0644)
    f.puts p   #Process.pid
  }
end

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