Class: Demon::Base

Inherits:
Object
  • Object
show all
Defined in:
lib/demon/base.rb

Overview

intelligent fork based demonizer

Direct Known Subclasses

EmailSync, RailsAutospec, Sidekiq

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(index, rails_root: nil, parent_pid: nil, verbose: false) ⇒ Base

Returns a new instance of Base.



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# File 'lib/demon/base.rb', line 42

def initialize(index, rails_root: nil, parent_pid: nil, verbose: false)
  @index = index
  @pid = nil
  @parent_pid = parent_pid || Process.pid
  @started = false
  @stop_timeout = 10
  @rails_root = rails_root || Rails.root
  @verbose = verbose
end

Instance Attribute Details

#indexObject (readonly)

Returns the value of attribute index.



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# File 'lib/demon/base.rb', line 39

def index
  @index
end

#parent_pidObject (readonly)

Returns the value of attribute parent_pid.



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# File 'lib/demon/base.rb', line 39

def parent_pid
  @parent_pid
end

#pidObject (readonly)

Returns the value of attribute pid.



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# File 'lib/demon/base.rb', line 39

def pid
  @pid
end

#startedObject (readonly)

Returns the value of attribute started.



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# File 'lib/demon/base.rb', line 39

def started
  @started
end

#stop_timeoutObject

Returns the value of attribute stop_timeout.



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# File 'lib/demon/base.rb', line 40

def stop_timeout
  @stop_timeout
end

Class Method Details

.alive?(pid) ⇒ Boolean

Returns:

  • (Boolean)


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# File 'lib/demon/base.rb', line 169

def self.alive?(pid)
  Process.kill(0, pid)
  true
rescue StandardError
  false
end

.demonsObject



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# File 'lib/demon/base.rb', line 8

def self.demons
  @demons
end

.ensure_runningObject



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# File 'lib/demon/base.rb', line 30

def self.ensure_running
  @demons.values.each { |demon| demon.ensure_running }
end

.kill(signal) ⇒ Object



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# File 'lib/demon/base.rb', line 34

def self.kill(signal)
  return unless @demons
  @demons.values.each { |demon| demon.kill(signal) }
end

.restartObject



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# File 'lib/demon/base.rb', line 22

def self.restart
  return unless @demons
  @demons.values.each do |demon|
    demon.stop
    demon.start
  end
end

.start(count = 1, verbose: false) ⇒ Object



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# File 'lib/demon/base.rb', line 12

def self.start(count = 1, verbose: false)
  @demons ||= {}
  count.times { |i| (@demons["#{prefix}_#{i}"] ||= new(i, verbose: verbose)).start }
end

.stopObject



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# File 'lib/demon/base.rb', line 17

def self.stop
  return unless @demons
  @demons.values.each { |demon| demon.stop }
end

Instance Method Details

#alive?(pid = nil) ⇒ Boolean

Returns:

  • (Boolean)


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# File 'lib/demon/base.rb', line 56

def alive?(pid = nil)
  pid ||= @pid
  if pid
    Demon::Base.alive?(pid)
  else
    false
  end
end

#already_running?Boolean

Returns:

  • (Boolean)


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# File 'lib/demon/base.rb', line 160

def already_running?
  if File.exist? pid_file
    pid = File.read(pid_file).to_i
    return pid if Demon::Base.alive?(pid)
  end

  nil
end

#ensure_runningObject



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# File 'lib/demon/base.rb', line 113

def ensure_running
  return unless @started

  if !@pid
    @started = false
    start
    return
  end

  dead =
    begin
      Process.waitpid(@pid, Process::WNOHANG)
    rescue StandardError
      -1
    end
  if dead
    STDERR.puts "Detected dead worker #{@pid}, restarting..."
    @pid = nil
    @started = false
    start
  end
end

#kill(signal) ⇒ Object



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# File 'lib/demon/base.rb', line 65

def kill(signal)
  Process.kill(signal, @pid)
end

#pid_fileObject



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# File 'lib/demon/base.rb', line 52

def pid_file
  "#{@rails_root}/tmp/pids/#{self.class.prefix}_#{@index}.pid"
end

#runObject



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# File 'lib/demon/base.rb', line 149

def run
  @pid =
    fork do
      Process.setproctitle("discourse #{self.class.prefix}")
      monitor_parent
      establish_app
      after_fork
    end
  write_pid_file
end

#startObject



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# File 'lib/demon/base.rb', line 136

def start
  return if @pid || @started

  if existing = already_running?
    # should not happen ... so kill violently
    STDERR.puts "Attempting to kill pid #{existing}"
    Process.kill("TERM", existing)
  end

  @started = true
  run
end

#stopObject



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# File 'lib/demon/base.rb', line 73

def stop
  @started = false
  if @pid
    Process.kill(stop_signal, @pid)

    wait_for_stop =
      lambda do
        timeout = @stop_timeout

        while alive? && timeout > 0
          timeout -= (@stop_timeout / 10.0)
          sleep(@stop_timeout / 10.0)
          begin
            Process.waitpid(@pid, Process::WNOHANG)
          rescue StandardError
            -1
          end
        end

        begin
          Process.waitpid(@pid, Process::WNOHANG)
        rescue StandardError
          -1
        end
      end

    wait_for_stop.call

    if alive?
      STDERR.puts "Process would not terminate cleanly, force quitting. pid: #{@pid} #{self.class}"
      Process.kill("KILL", @pid)
    end

    wait_for_stop.call

    @pid = nil
    @started = false
  end
end

#stop_signalObject



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# File 'lib/demon/base.rb', line 69

def stop_signal
  "HUP"
end