sigwinch and screen

Eric Wong normalperson at
Wed Sep 14 13:32:13 EDT 2011

Brian P O'Rourke <bpo at> wrote:
> (my apologies if this gets posted twice - don't think my earlier mail
> went through)

I've noticed rubyforge has occasional slowness :<   It uses Postgrey so
first time posters could be delayed...

> I'm running unicorn within screen and have run into some trouble.
> Unicorn tries to ignore sigwinch when it's not daemonized.
> Unfortunately the check for daemonization fails when unicorn is exec'd
> from a process that already has a pgrp.
> You can simulate this problem from *within* a screen session with
> something like this:
>     screen sleep 5 && screen bundle exec unicorn -c unicorn.conf

So, start "screen", get a terminal + shell, /then/ type the above?

> sigwinch will be sent to the second screen session the first time you
> change to it. This doesn't happen unless you launch at least two
> screens in rapid succession, for reasons that escape me so far -
> haven't dug into that part much yet.

I haven't been able to reproduce it on my end.
It could be system-dependent (terminals are often wonky/inconsistent).

> It seems to me that this is a problem, and is occurring because
> Unicorn's check for daemonization is "is init my parent or is my group
> different from my pid?", which isn't necessarily the same as checking
> whether daemonization has happened.

Agreed.  Regardless of what the problem is, I like your check based on
RACKUP[:daemonized].  It's much more readable and obvious :)

> Here is the patch I would like to see applied:

I'll apply it.   Is there a commit message you'd like to use?
(Otherwise I'll just edit something based on your email)


> --- a/lib/unicorn/http_server.rb
> +++ b/lib/unicorn/http_server.rb
> @@ -282,7 +282,7 @@ class Unicorn::HttpServer
>        when :USR2 # exec binary, stay alive in case something went wrong
>          reexec
>        when :WINCH
> -        if Process.ppid == 1 || Process.getpgrp != $$
> +        if Unicorn::Configurator::RACKUP[:daemonized]
>            respawn = false
>   "gracefully stopping all workers"
>            kill_each_worker(:QUIT)
Eric Wong

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