RAILS_ROOT and USR2 restarts

Eric Wong normalperson at yhbt.net
Mon Oct 26 12:01:58 EDT 2009


Ian Leitch <port001 at gmail.com> wrote:
> Hi,
> 
> I've just started using Unicorn in production behind Nginx with a
> Rails app, for the most part its been a smooth transition apart from
> this one issue.
> When I do an in place restart (USR2), the restart process works but
> the workers load my old Rails release, not the new one. I'm guessing
> that because the master process is currently in the old release
> directory, when I signal USR2 it's just reloading inside the current
> directory. I'm deploying with Capistrano, so app/current is a symlink
> to a specific release. I've tried changing to the new release
> directory in before_work but that made no difference. Is there a
> callback that fires before the master preloads the app?

Hi Ian,

Unicorn chdirs to the directory returned by `/bin/sh -c pwd` when it was
originally started.  The output of `pwd` *should* be symlink-aware, but
then Solaris /bin/sh is weird.  Can you confirm that it's broken?

You can put the following in your config (outside of the hooks):

  app_root = "/var/www/apps/systino_production/current"
  Dir.chdir(Unicorn::HttpServer::START_CTX[:cwd] = app_root)

I've been pondering adding a "working_directory" directive to
Configurator, too.  However the START_CTX hash is considered a stable
interface and I recently documented it in
http://unicorn.bogomips.org/Unicorn.html

START_CTX even allows you to switch between different installation paths
for Unicorn[1] and alter command line options that were originally
passed.  Lots of rope there :>

[1] for different Ruby installs/versions,
    or even swap in Rainbows! or vice versa

-- 
Eric Wong


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