Merge branch 'improve-mail_room-wrapper' into 'master'

Properly daemonize the mail_room process

The old invocation only worked by accident because we have a '&'
somewhere in the init script for expediency. When ran from a terminal,
the mail_room daemon process ended up in the session of the terminal.
This commit adds a small wrapper that tries to do the textbook
daemonization steps (double fork, setsid etc.) while also taking
care that the pidfile is written before the 'start' process exits.

See merge request !1221

bin/daemon_with_pidfile

+#!/usr/bin/env ruby
+# daemon_with_pidfile
+#
+# Daemonize, write a pidfile, and exec the remainder of the command line.
+
+def main(pidfile, cmd)
+  if middle_pid = Process.fork
+    # outer process
+    # Do not exit the outer process before the middle process finishes
+    Process.waitpid(middle_pid)
+    exit $?.exitstatus
+  end
+
+  if final_pid = Process.fork
+    # middle process
+    open(pidfile, 'w') { |f| f.puts final_pid }
+    exit
+  end
+
+  # Standard daemon things: become session leader, ignore SIGHUP, close stdin.
+  Signal.trap("HUP", "IGNORE")
+  Process.setsid
+  IO.new(0).close
+
+  exec(*cmd)
+end
+
+if ARGV.count < 2
+  abort "Usage: #$0 pidfile command [args...]"
+end
+
+pidfile = ARGV.shift
+main(pidfile, ARGV)

bin/mail_room

@@ -19,9 +19,7 @@ get_mail_room_pid()
 
 start()
 {
-  bundle exec mail_room -q -c $mail_room_config >> $mail_room_logfile 2>&1 &
-  PID=$!
-  echo $PID > $mail_room_pidfile
+  bin/daemon_with_pidfile $mail_room_pidfile bundle exec mail_room -q -c $mail_room_config >> $mail_room_logfile 2>&1
 }
 
 stop()