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From: Eric Wong <e@80x24.org>
To: =?utf-8?Q?Br=C3=A1ulio?= Bhavamitra <braulio@eita.org.br>
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Subject: Re: Master hooks needed
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Bráulio Bhavamitra <braulio@eita.org.br> wrote:
> I think the hook is needed because I took too much time to figure out
> the problem and much more time to figure out the solution (this
> master_run variable). Also, I don't think this master_run solution is
> elegant.

A guard variable is fairly common practice for initialization.
It's not always nice, but I do not consider the existing hooks
to be elegant, either; they're only unfortunately necessary.

I consider having redundant features to be even worse.

How about the following documentation change instead?

--- a/examples/unicorn.conf.rb
+++ b/examples/unicorn.conf.rb
@@ -54,12 +54,23 @@ GC.respond_to?(:copy_on_write_friendly=) and
 # fast LAN.
 check_client_connection false
 
+# local variable to guard against running a hook multiple times
+run_once = true
+
 before_fork do |server, worker|
   # the following is highly recomended for Rails + "preload_app true"
   # as there's no need for the master process to hold a connection
   defined?(ActiveRecord::Base) and
     ActiveRecord::Base.connection.disconnect!
 
+  # Occasionally, it may be necessary to run non-idempotent code in the
+  # master before forking.  Keep in mind the above disconnect! example
+  # is idempotent and does not need a guard.
+  if run_once
+    # do_something_once_here ...
+    run_once = false # prevent from firing again
+  end
+
   # The following is only recommended for memory/DB-constrained
   # installations.  It is not needed if your system can house
   # twice as many worker_processes as you have configured.