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>.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 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)

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Pid

dir, running?

Constructor Details

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

Returns a new instance of PidFile.



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# File 'lib/daemons/pidfile.rb', line 56

def initialize(dir, progname, multiple = false)
  @dir = File.expand_path(dir)
  @progname = progname
  @multiple = multiple
  @number = 0 if multiple
end

Instance Attribute Details

#dir ⇒ Object (readonly)

Returns the value of attribute dir.



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

def dir
  @dir
end

#multiple ⇒ Object (readonly)

Returns the value of attribute multiple.



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

def multiple
  @multiple
end

#number ⇒ Object (readonly)

Returns the value of attribute number.



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

def number
  @number
end

#progname ⇒ Object (readonly)

Returns the value of attribute progname.



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

def progname
  @progname
end

Class Method Details

.existing(path) ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 44

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) ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 36

def PidFile.find_files(dir, progname)
  files = Dir[File.join(dir, "#{progname}*.pid")]
  
  files.delete_if {|f| not (File.file?(f) and File.readable?(f))}
  
  return files
end

Instance Method Details

#cleanup ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 87

def cleanup
  File.delete(filename)
end

#exists? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/daemons/pidfile.rb', line 67

def exists?
  File.exists? filename
end

#filename ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 63

def filename
  File.join(@dir, "#{@progname}#{ @number or '' }.pid")
end

#pid ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 91

def pid
  File.open(filename) {|f|
    return f.gets.to_i
  }
end

#pid=(p) ⇒ Object 



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# File 'lib/daemons/pidfile.rb', line 71

def pid=(p)
  if multiple
    while File.exists?(filename) and @number < 1024
      @number += 1
    end
    
    if @number == 1024
      raise RuntimeException('cannot run more than 1024 instances of the application')
    end
  end
  
  File.open(filename, 'w') {|f|
    f.puts p   #Process.pid
  }
end