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.

Properly daemonize the mail_room process
1081a322 · Jacob Vosmaer · abb5b9f6 · 1081a322 · 1081a322
Commit 1081a322 authored Aug 27, 2015 by Jacob Vosmaer
Hide whitespace changes
Inline Side-by-side

Showing with 34 additions and 3 deletions

daemon_with_pidfile bin/daemon_with_pidfile +33 -0

mail_room bin/mail_room +1 -3

No files found.
--- a/bin/daemon_with_pidfile
+++ b/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)
--- a/bin/mail_room
+++ b/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()