Class: Daemons::PidFile

Inherits:
Pid
  • Object
show all
Defined in:
lib/daemons/pidfile.rb

Overview

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>_num<number>.pid

(Note that _num<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)

Constant Summary collapse

DEFAULT_PID_DELIMITER = 
'_num'

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Pid

dir, running?, #running?

Constructor Details

#initialize(dir, progname, multiple = false, pid_delimiter = nil) ⇒ PidFile

Returns a new instance of PidFile.



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# File 'lib/daemons/pidfile.rb', line 66

def initialize(dir, progname, multiple = false, pid_delimiter = nil)
  @dir = File.expand_path(dir)
  @progname = progname
  @multiple = multiple
  @pid_delimiter = pid_delimiter || DEFAULT_PID_DELIMITER
  @number = nil
  @number = 0 if multiple

  if multiple
    while File.exist?(filename) && @number < 1024
      @number += 1
    end

    if @number >= 1024
      fail RuntimeException('cannot run more than 1024 instances of the application')
    end
  end
end

Instance Attribute Details

#dir ⇒ Object (readonly)

Returns the value of attribute dir.



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# File 'lib/daemons/pidfile.rb', line 32

def dir
  @dir
end

#multiple ⇒ Object (readonly)

Returns the value of attribute multiple.



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# File 'lib/daemons/pidfile.rb', line 32

def multiple
  @multiple
end

#number ⇒ Object (readonly)

Returns the value of attribute number.



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# File 'lib/daemons/pidfile.rb', line 32

def number
  @number
end

#pid_delimiter ⇒ Object (readonly)

Returns the value of attribute pid_delimiter.



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# File 'lib/daemons/pidfile.rb', line 32

def pid_delimiter
  @pid_delimiter
end

#progname ⇒ Object (readonly)

Returns the value of attribute progname.



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# File 'lib/daemons/pidfile.rb', line 32

def progname
  @progname
end

Class Method Details

.existing(path) ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 54

def self.existing(path)
  new_instance = PidFile.allocate

  new_instance.instance_variable_set(:@path, path)

  def new_instance.filename
    @path
  end

  new_instance
end

.find_files(dir, progname, delete = false, pid_delimiter = nil) ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 34

def self.find_files(dir, progname, delete = false, pid_delimiter = nil)
  files = Dir[File.join(dir, "#{progname}#{pid_delimiter || DEFAULT_PID_DELIMITER}*.pid")]
  files = Dir[File.join(dir, "#{progname}.pid")] if files.size == 0

  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
        begin; File.unlink(f); rescue ::Exception; end
        yield(pid, f) if block_given?
      end
      rsl
    end
  end

  files
end

Instance Method Details

#cleanup ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 101

def cleanup
  File.delete(filename) if pid == Process.pid
end

#exist? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/daemons/pidfile.rb', line 90

def exist?
  File.exist? filename
end

#filename ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 85

def filename
  suffix = "#{pid_delimiter}#{@number}" if @number
  File.join(@dir, "#{@progname}#{suffix}.pid")
end

#pid ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 109

def pid
  begin
    File.open(filename) do |f|
      p = f.gets.to_i
      return nil if p == 0  # Otherwise an invalid pid file becomes pid 0
      return p
    end
  rescue ::Exception
    return nil
  end
end

#pid=(p) ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 94

def pid=(p)
  File.open(filename, 'w') do |f|
    f.chmod(0644)
    f.puts p   # Process.pid
  end
end

#zap ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 105

def zap
  File.delete(filename) if exist?
end