Class: Opener::Daemons::Pidfile

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

Overview

Class for writing and retrieving PID files as well as managing the associated process.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(path) ⇒ Pidfile

Returns a new instance of Pidfile.

Parameters:

  • path (String) 


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# File 'lib/opener/daemons/pidfile.rb', line 17

def initialize(path)
  @path = path
end

Instance Attribute Details

#path ⇒ String (readonly)

The path to store the PID in.

Returns:

  • (String) 


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# File 'lib/opener/daemons/pidfile.rb', line 11

class Pidfile
  attr_reader :path

  ##
  # @param [String] path
  #
  def initialize(path)
    @path = path
  end

  ##
  # Writes the given process ID to `@path`.
  #
  # @param [Fixnum] id
  #
  def write(id)
    File.open(path, 'w') do |handle|
      handle.write(id.to_s)
    end

  # Kill the process immediately if we couldn't write the PID
  rescue Errno::ENOENT, Errno::EPERM => error
    Process.kill('KILL', id)
  end

  ##
  # Reads and returns the process ID.
  #
  # @return [Fixnum]
  #
  def read
    return File.read(path).to_i
  end

  ##
  # Removes the associated file, if it exists.
  #
  def unlink
    File.unlink(path) if File.file?(path)
  end

  ##
  # Terminates the process by sending it the TERM signal and waits for it to
  # shut down.
  #
  def terminate
    id = read

    begin
      Process.kill('TERM', id)
      Process.wait(id)
    rescue Errno::ESRCH, Errno::ECHILD
      # Process terminated, yay. Any other error is re-raised.
    end
  end

  ##
  # Returns `true` if the associated process is alive.
  #
  # @return [TrueClass|FalseClass]
  #
  def alive?
    id = read

    begin
      Process.kill(0, id)

      return true
    rescue Errno::ESRCH, Errno::EPERM
      return false
    end
  end
end

Instance Method Details

#alive? ⇒ TrueClass|FalseClass

Returns ‘true` if the associated process is alive.

Returns:

  • (TrueClass|FalseClass) 


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# File 'lib/opener/daemons/pidfile.rb', line 72

def alive?
  id = read

  begin
    Process.kill(0, id)

    return true
  rescue Errno::ESRCH, Errno::EPERM
    return false
  end
end

#read ⇒ Fixnum

Reads and returns the process ID.

Returns:

  • (Fixnum) 


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# File 'lib/opener/daemons/pidfile.rb', line 41

def read
  return File.read(path).to_i
end

#terminate ⇒ Object

Terminates the process by sending it the TERM signal and waits for it to shut down.



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

def terminate
  id = read

  begin
    Process.kill('TERM', id)
    Process.wait(id)
  rescue Errno::ESRCH, Errno::ECHILD
    # Process terminated, yay. Any other error is re-raised.
  end
end

#unlink ⇒ Object

Removes the associated file, if it exists.



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# File 'lib/opener/daemons/pidfile.rb', line 48

def unlink
  File.unlink(path) if File.file?(path)
end

#write(id) ⇒ Object

Writes the given process ID to ‘@path`.

Parameters:

  • id (Fixnum) 


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# File 'lib/opener/daemons/pidfile.rb', line 26

def write(id)
  File.open(path, 'w') do |handle|
    handle.write(id.to_s)
  end

# Kill the process immediately if we couldn't write the PID
rescue Errno::ENOENT, Errno::EPERM => error
  Process.kill('KILL', id)
end