Comments on: Making sure Ruby Daemons die

By: gemFinder

gemFinder — Mon, 21 Jun 2010 00:04:14 +0000

great extension , thanks

By: links for 2010-02-09 « Bloggitation

links for 2010-02-09 « Bloggitation — Wed, 10 Feb 2010 06:05:33 +0000

[...] Making sure Ruby Daemons die (tags: ruby sysadmin) [...]

By: Irish

Irish — Tue, 15 Dec 2009 23:03:20 +0000

Thanks Chris and Seamus, this fix & gem was exactly what I needed

By: The Daemons are Dead (long live the Daemons) « reevoolabs

The Daemons are Dead (long live the Daemons) « reevoolabs — Tue, 24 Nov 2009 17:50:38 +0000

[...] This problem has thankfully been solved by the use of RapLeafs’ daemon_extension code which is basically a bundle of hacks to kill -9 a daemon that refuses to die after a certain timeout period. This isn’t perfect by any stretch of the imagination, but from a pragmatists point of view: It’ll do! [...]

By: Greg Hazel

Greg Hazel — Wed, 26 Aug 2009 19:59:18 +0000

As Tony said, that is just a wait function. In fact, the Daemons library already uses kill(0, pid) to implement Daemons::Pid.running?(pid), and as noted there kill(0, pid) does not send a signal; it’s just a syscall to see if a signal may be sent.

So you can see where it fits into the Daemons code, and so there’s a gem, I’ve made a github repo out of the Daemons SVN repository:
http://github.com/ghazel/daemons/

Here is the relevant commit:
http://github.com/ghazel/daemons/commit/3e91f91c5a95409bdbd54039e4163ea509d66619

By: Brian Armstrong

Brian Armstrong — Wed, 12 Aug 2009 01:43:54 +0000

Thanks for posting this, I was having the same problem.

I ended up switching to the daemons-spawn gem instead using instructions here and that also fixed it:
http://rwldesign.com/journals/1-solutions/posts/24-working-with-delayed-job

One drawback is the daemons-gem script doesn’t (yet) support multiple workers with a -n option (it only launches one). Probably wouldn’t be too hard to modify it. Anyway, just wanted to post another solution.

delayed_job should really update their daemonizing instructions on github! As evidenced by this thread, what they have posted is not stable in production.

Thanks!
Brian
http://feedmailpro.com

By: Tony Payne

Tony Payne — Wed, 22 Jul 2009 03:06:37 +0000

Note that Greg’s code is merely a wait function, not a kill. It continues to loop as long as the process exists. kill -0 does not signal the process, but instead returns true if the process is alive, false otherwise. It’s a pretty standard kill value.

By: Mike Ayers

Mike Ayers — Mon, 20 Jul 2009 23:51:12 +0000

Signal 0 is, as best I can tell, a meta-signal that causes an exception if the process does not exist. I saw it in some Ruby code, which I copied, then discovered that this signal is not only not POSIX, it’s not even uniformly supported on Linux! I think Greg meant “Process.kill(‘TERM’, pid)”, as signal 0 would not stop anything.

By: chris

chris — Sun, 08 Mar 2009 17:21:49 +0000

Hi Greg,
We’re always looking for ways to simplify code, so thanks for the ideas. I have a couple of questions:

1. What signal does ‘0′ correspond to (in ‘Process.kill(0, pid)’)? On both my Mac and CentOS, TERM is ‘15′ and KILL is ‘9′. Maybe I’m just missing something…
2. Does this work with :multiple => true? Perhaps it would help to see where this fits into the Daemons code.

Our use cases might be very different, but it is important for us to receive feedback via STDOUT along the way. In your solution, we could just add a ‘puts’ in the while loop, but we probably wouldn’t want that message to appear 10 times a second. That brings up another subtle difference. In your solution, a signal is sent after every sleep period. In our solution we send a TERM signal, then wait a configurable amount of time for the process to exit gracefully before sending the KILL signal.

By: Greg Hazel

Greg Hazel — Fri, 27 Feb 2009 09:14:36 +0000

Ok, more than one line. Process.wait doesn’t work because the pid is not a child of the process that is stopping everything. Instead you need:

def fancy_wait pid
begin
while (1) do
Process.kill(0, pid)
sleep 0.1
end
rescue Errno::ESRCH, Errno::ECHILD
end
end