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From: Eric Wong <e@80x24.org>
To: "Bráulio Bhavamitra" <braulio@eita.org.br>
Cc: unicorn-public <unicorn-public@bogomips.org>
Subject: Re: Master hooks needed
Date: Fri, 3 Oct 2014 12:22:22 +0000	[thread overview]
Message-ID: <20141003122222.GA11445@dcvr.yhbt.net> (raw)
In-Reply-To: <CAJri6_tdtd5tfPcrTcTBbmQKrmRYnnGJERFwSo1T6PTDsoOO_A@mail.gmail.com>

Bráulio Bhavamitra <braulio@eita.org.br> wrote:
> Hello all,
> If I need to hook something after master load, I'm currently doing:
> before_fork do |server, worker|
>   # worker 0 is the first to init, so hold the master here
>   if worker.nr == 0
>      #warm up server...
>      #kill old pid...
>   end
>   # other stuff for each worker
> end
> Both operations I currently do (server warm up and old pid kill) need
> to be run only once, and not for every worker as before_fork does,
> that's why I had to put the condition seen above.

The above is fine if your first worker never dies.  I think you can add
a local variable to ensure it only runs the first time worker.nr == 0 is
started, in case a worker dies.  Something like:

    first = true
    before_fork do |server, worker|
      # worker 0 is the first to init, so hold the master here
      if worker.nr == 0 && first
         first = false
         #warm up server...

         #kill old pid...

      # other stuff for each worker

For what it's worth, I'm not a fan of auto-killing the old PID in the
unicorn config and regret having it in the example config.  It's only
for the most memory-constrained configs and fragile (because anything
with pid files is always fragile).

> So hooks for master is needed, something like
> master_after_load(server) and master_init(server).
> What do you think?

rack.git also has a Rack::Builder#warmup method.  Aman originally
proposed it for unicorn, but it's useful outside of unicorn so
we moved it to Rack.

In general, I'm against adding new hooks/options because they tend to
make maintainability and documentation harder for ops folks.
I still have nightmares of some Capistrano config filled with hooks
from years ago :x

Features like these also makes migrating away from unicorn harder, so
that is another reason we ended up adding #warmup to Rack and not

  reply	other threads:[~2014-10-03 12:22 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-03 11:34 Master hooks needed Bráulio Bhavamitra
2014-10-03 12:22 ` Eric Wong [this message]
2014-10-03 12:36   ` Valentin Mihov
2014-10-03 17:50     ` Eric Wong
2014-10-03 18:12       ` Valentin Mihov
2014-10-04  0:53   ` Bráulio Bhavamitra
2014-10-04  1:22     ` Eric Wong
2014-10-04  1:35       ` Bráulio Bhavamitra
2014-10-04  1:57         ` Eric Wong
2014-10-04  2:04           ` Bráulio Bhavamitra
2014-10-04  2:25             ` Eric Wong

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