unicorn worker partially restarted when using USR2

unicorn worker partially restarted when using USR2

[Stone]

In the deployment I did kill -s USR2 `cat unicorn_pid` to gracefully
restart unicorn. But I noticed that unicorn workers were partially
restarted when using USR2.

The following is how I did test:

start unicorn in production environment:

the action has the following code:

  def index
    logger.info "-----------------------------------------fooo bar ---------"
    logger.info "-----------------------------------fooo bar ---------"
  end

then  changed the code to:

  def index
    logger.info "--####---------------------------------fooo bar ---------"
    logger.info "-----------------------------------fooo bar ---------"
  end

and run kill -s USR2 `cat unicorn_pid`

and then tail the production.log  (after several minutes)


Started GET "/" for 192.168.21.1 at Sat May 07 04:13:31 -0700 2011
  Processing by NewHomeController#index as HTML
-----------------------------------fooo bar ---------
-----------------------------------fooo bar ---------
Rendered new_home/index.html.erb within layouts/new_home (15.5ms)
Completed 200 OK in 16ms (Views: 16.2ms)


Started GET "/" for 192.168.21.1 at Sat May 07 04:13:31 -0700 2011
  Processing by NewHomeController#index as HTML
--####---------------------------------fooo bar ---------
-----------------------------------fooo bar ---------
Rendered new_home/index.html.erb within layouts/new_home (28.1ms)
Completed 200 OK in 29ms (Views: 28.9ms)


Started GET "/" for 192.168.21.1 at Sat May 07 04:13:31 -0700 2011
  Processing by NewHomeController#index as HTML
-----------------------------------fooo bar ---------
-----------------------------------fooo bar ---------
Rendered new_home/index.html.erb within layouts/new_home (17.5ms)
Completed 200 OK in 20ms (Views: 18.4ms)


Started GET "/" for 192.168.21.1 at Sat May 07 04:13:37 -0700 2011
  Processing by NewHomeController#index as HTML
--####---------------------------------fooo bar ---------
-----------------------------------fooo bar ---------
Rendered new_home/index.html.erb within layouts/new_home (13.5ms)


So it seems that unicorn was just partially restarted.


Best Regards,
Stone
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Re: unicorn worker partially restarted when using USR2

[Eric Wong]

Stone <stones.gao@gmail.com> wrote:
> In the deployment I did kill -s USR2 `cat unicorn_pid` to gracefully
> restart unicorn. But I noticed that unicorn workers were partially
> restarted when using USR2.

You need to send a SIGQUIT to the original master process, otherwise
both masters and all workers continue running.  This allows you to test
the new deploy (combined with SIGWINCH).

The last section of http://unicorn.bogomips.org/SIGNALS.html
describes this process in detail.

> The following is how I did test:
> 
> start unicorn in production environment:
> 
> the action has the following code:

Ugh, don't you have something like "ps axf" that shows you a process
tree?  It's much easier just to *see* the process tree.

-- 
Eric Wong
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