module Demon; end # intelligent fork based demonizer class Demon::Base def self.demons @demons end def self.start(count = 1, verbose: false) @demons ||= {} count.times do |i| (@demons["#{prefix}_#{i}"] ||= new(i, verbose: verbose)).start end end def self.stop return unless @demons @demons.values.each do |demon| demon.stop end end def self.restart return unless @demons @demons.values.each do |demon| demon.stop demon.start end end def self.ensure_running @demons.values.each do |demon| demon.ensure_running end end attr_reader :pid, :parent_pid, :started, :index attr_accessor :stop_timeout 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 def pid_file "#{@rails_root}/tmp/pids/#{self.class.prefix}_#{@index}.pid" end def alive?(pid = nil) pid ||= @pid if pid Demon::Base.alive?(pid) else false end end def stop_signal "HUP" end def stop @started = false if @pid Process.kill(stop_signal, @pid) wait_for_stop = lambda { timeout = @stop_timeout while alive? && timeout > 0 timeout -= (@stop_timeout / 10.0) sleep(@stop_timeout / 10.0) Process.waitpid(@pid, Process::WNOHANG) rescue -1 end Process.waitpid(@pid, Process::WNOHANG) rescue -1 } 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 def ensure_running return unless @started if !@pid @started = false start return end dead = Process.waitpid(@pid, Process::WNOHANG) rescue -1 if dead STDERR.puts "Detected dead worker #{@pid}, restarting..." @pid = nil @started = false start end end 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 def run if @pid = fork write_pid_file return end monitor_parent establish_app after_fork end def already_running? if File.exists? pid_file pid = File.read(pid_file).to_i if Demon::Base.alive?(pid) return pid end end nil end def self.alive?(pid) Process.kill(0, pid) true rescue false end private def verbose(msg) if @verbose puts msg end end def write_pid_file verbose("writing pid file #{pid_file} for #{@pid}") FileUtils.mkdir_p(@rails_root + "tmp/pids") File.open(pid_file, 'w') do |f| f.write(@pid) end end def delete_pid_file File.delete(pid_file) end def monitor_parent Thread.new do while true begin unless alive?(@parent_pid) Process.kill "TERM", Process.pid sleep 10 Process.kill "KILL", Process.pid end rescue => e STDERR.puts "URGENT monitoring thread had an exception #{e}" end sleep 1 end end end def suppress_stdout true end def suppress_stderr true end def establish_app Discourse.after_fork if defined?(Discourse) Signal.trap("HUP") do begin delete_pid_file ensure # TERM is way cleaner than exit Process.kill("TERM", Process.pid) end end # keep stuff simple for now $stdout.reopen("/dev/null", "w") if suppress_stdout $stderr.reopen("/dev/null", "w") if suppress_stderr end def after_fork end end