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

Public Class Methods

existing(path) click to toggle source
    # File lib/daemons/pidfile.rb, line 55
55:     def PidFile.existing(path)
56:       new_instance = PidFile.allocate
57:       
58:       new_instance.instance_variable_set(:@path, path)
59:       
60:       def new_instance.filename
61:         return @path
62:       end
63:       
64:       return new_instance
65:     end
find_files(dir, progname, delete = false) click to toggle source
    # File lib/daemons/pidfile.rb, line 36
36:     def PidFile.find_files(dir, progname, delete = false)
37:       files = Dir[File.join(dir, "#{progname}*.pid")]
38:       
39:       files.delete_if {|f| not (File.file?(f) and File.readable?(f))}
40:       if delete 
41:         files.delete_if do |f|
42:           pid = File.open(f) {|h| h.read}.to_i
43:           rsl =  ! Pid.running?(pid)
44:           if rsl
45:             puts "pid-file for killed process #{pid} found (#{f}), deleting."
46:             begin; File.unlink(f); rescue ::Exception; end
47:           end
48:           rsl
49:         end
50:       end
51:     
52:       return files
53:     end
new(dir, progname, multiple = false) click to toggle source
    # File lib/daemons/pidfile.rb, line 67
67:     def initialize(dir, progname, multiple = false)
68:       @dir = File.expand_path(dir)
69:       @progname = progname
70:       @multiple = multiple
71:       @number = nil
72:       @number = 0 if multiple
73:       
74:       if multiple
75:         while File.exist?(filename) and @number < 1024
76:           @number += 1
77:         end
78:         
79:         if @number == 1024
80:           raise RuntimeException('cannot run more than 1024 instances of the application')
81:         end
82:       end
83:     end

Public Instance Methods

cleanup() click to toggle source
     # File lib/daemons/pidfile.rb, line 100
100:     def cleanup
101:       File.delete(filename) if pid == Process.pid
102:     end
exist?() click to toggle source
    # File lib/daemons/pidfile.rb, line 89
89:     def exist?
90:       File.exist? filename
91:     end
filename() click to toggle source
    # File lib/daemons/pidfile.rb, line 85
85:     def filename
86:       File.join(@dir, "#{@progname}#{ @number or '' }.pid")
87:     end
pid() click to toggle source
     # File lib/daemons/pidfile.rb, line 104
104:     def pid
105:       begin
106:         File.open(filename) {|f|
107:           return f.gets.to_i
108:         }
109:       rescue ::Exception
110:         return nil
111:       end
112:     end
pid=(p) click to toggle source
    # File lib/daemons/pidfile.rb, line 93
93:     def pid=(p)
94:       File.open(filename, 'w') {|f|
95:         f.chmod(0644)
96:         f.puts p   #Process.pid
97:       }
98:     end

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