[Devel] [Fwd: Re: [Serdev] main_loop() initialization order]

[Klaus Darilion]

Does this address openser too?

regards
klaus

-------- Original Message --------
Subject: Re: [Serdev] main_loop() initialization order
Date: Wed, 14 Feb 2007 14:14:16 +0100
From: Jan Janak <jan at iptel.org>
To: Jan Andres <jan.andres at freenet-ag.de>
CC: serdev at iptel.org
References: <20070213085456.GA26505 at localhost.localdomain>

Jan Andres wrote:
> Hi,
> 
> We have found a bug in SER and are currently a bit unsure what is the
> correct approach to fix it.
> 
> The problem: main_loop() must call init_child() from the main process
> before forking off the TCP listener processes. init_child() will call
> the child initialization functions of all the loaded modules, and some
> of them may open database sessions. The TCP listeners will inherit these
> sessions after the fork(), so all TCP listeners attempt to communicate
> with the database over the same TCP session, which of course fails sooner
> or later, producing weird errors that are quite hard to debug.
> 
> This problem was specifically observed with the usrloc module, but it
> likely affects other modules as well.
> 
> Potential solutions:
> 1. Fix all modules so that they don't open database sessions when their
>    child init functions are called in PROC_MAIN. Also, database sessions
>    are possibly not be the only thing affected by this issue.
> 2. Never run any modules' child_init_function when init_child(PROC_MAIN)
>    is called. As far as I can see, after it has forked all the children,
>    the main process does nothing but signal handling, so there should be
>    no need to init the modules for that process.
> 
> What are the list's opinions on this?

   It appears to me that the problem is in child_init being called before
   fork. I am not sure why does that happen in TCP listeners (this is
   probably a question for Andrei), but child_init functions should be
   called after the fork (only mod_init is called before fork). All
   modules assume this behavior and hence open database connections from
   child_init (to avoid inherited database connections).

   Thanks for the report, we will take a look at it.

     Jan.
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-- 
Klaus Darilion
nic.at