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

Constant Summary collapse

HOSTNAME =
Socket.gethostname

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

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

Returns a new instance of Base.



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# File 'lib/demon/base.rb', line 55

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

Instance Attribute Details

#indexObject (readonly)

Returns the value of attribute index.



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

def index
  @index
end

#parent_pidObject (readonly)

Returns the value of attribute parent_pid.



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

def parent_pid
  @parent_pid
end

#pidObject (readonly)

Returns the value of attribute pid.



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

def pid
  @pid
end

#startedObject (readonly)

Returns the value of attribute started.



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

def started
  @started
end

#stop_timeoutObject

Returns the value of attribute stop_timeout.



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# File 'lib/demon/base.rb', line 53

def stop_timeout
  @stop_timeout
end

Class Method Details

.alive?(pid) ⇒ Boolean

Returns:

  • (Boolean)


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# File 'lib/demon/base.rb', line 199

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

.demonsObject



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# File 'lib/demon/base.rb', line 10

def self.demons
  @demons
end

.ensure_runningObject



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# File 'lib/demon/base.rb', line 43

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 47

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

.reset_demonsObject



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# File 'lib/demon/base.rb', line 19

def self.reset_demons
  @demons = {}
end

.restartObject



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# File 'lib/demon/base.rb', line 38

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

.set_demons(demons) ⇒ Object



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# File 'lib/demon/base.rb', line 15

def self.set_demons(demons)
  @demons = demons
end

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



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# File 'lib/demon/base.rb', line 28

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

.stopObject



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# File 'lib/demon/base.rb', line 33

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 74

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 190

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 139

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
    log("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 83

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

#log(message, level: :info) ⇒ Object



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# File 'lib/demon/base.rb', line 66

def log(message, level: :info)
  @logger.public_send(level, message)
end

#pid_fileObject



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# File 'lib/demon/base.rb', line 70

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

#restartObject



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# File 'lib/demon/base.rb', line 91

def restart
  stop
  start
end

#runObject



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# File 'lib/demon/base.rb', line 176

def run
  Discourse.before_fork if defined?(Discourse)

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

  write_pid_file
end

#set_pid(pid) ⇒ Object



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# File 'lib/demon/base.rb', line 23

def set_pid(pid)
  @pid = pid
end

#startObject



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# File 'lib/demon/base.rb', line 163

def start
  return if @pid || @started

  if existing = already_running?
    # should not happen ... so kill violently
    log("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 96

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?
      log(
        "Process would not terminate cleanly, force quitting. pid: #{@pid} #{self.class}\n#{caller.join("\n")}",
      )
      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 87

def stop_signal
  "HUP"
end