Module: Yahns::Daemon

Defined in:
lib/yahns/daemon.rb

Overview

:nodoc:

Class Method Summary collapse

Class Method Details

.daemon(yahns_server) ⇒ Object

We don’t do a lot of standard daemonization stuff:

* umask is whatever was set by the parent process at startup
  and can be set in config.ru and config_file, so making it
  0000 and potentially exposing sensitive log data can be bad
  policy.
* don't bother to chdir("/") here since yahns is designed to
  run inside APP_ROOT.  Yahns will also re-chdir() to
  the directory it was started in when being re-executed
  to pickup code changes if the original deployment directory
  is a symlink or otherwise got replaced.



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# File 'lib/yahns/daemon.rb', line 18

def self.daemon(yahns_server)
  $stdin.reopen("/dev/null")

  # We only start a new process group if we're not being reexecuted
  # and inheriting file descriptors from our parent
  if ENV['YAHNS_FD']
    # if we're inheriting, need to ensure this remains true so
    # SIGWINCH works when worker processes are in play
    yahns_server.daemon_pipe = true
  else
    # grandparent - reads pipe, exits when master is ready
    #  \_ parent  - exits immediately ASAP
    #      \_ yahns master - writes to pipe when ready

    # We cannot use Yahns::Sigevent (eventfd) here because we need
    # to detect EOF on unexpected death, not just read/write
    rd, wr = IO.pipe
    rd.close_on_exec = wr.close_on_exec = true
    grandparent = $$
    if fork
      wr.close # grandparent does not write
    else
      rd.close # yahns master does not read
      Process.setsid
      exit if fork # parent dies now
    end

    if grandparent == $$
      # this will block until Server#join runs (or it dies)
      master_pid = (rd.readpartial(16) rescue nil).to_i
      unless master_pid > 1
        warn "master failed to start, check stderr log for details"
        exit!
      end
      exit
    else # yahns master process
      yahns_server.daemon_pipe = wr
    end
  end
  # $stderr/$stderr can/will be redirected separately in the Yahns config
end