From: ara.t.howard@...
Date: 2007-03-05T06:12:47+09:00
Subject: Re: Strange interference between LSAPI, popen3 and MySQL

On Mon, 5 Mar 2007, Andreas Schwarz wrote:

> and reopen it after it to avoid problems.
>
>> i bet what happens is that the parent (rails) has setup an at_exit handler to
>> close the db on exit.
>
> That makes sense, although I couldn't find any reference to at_exit in
> Rails or ruby-lsapi.

huh - maybe it's the actuall c mysql driver.

>> i'd try putting this
>>    class Object
>>      alias_method '__fork__', 'fork'
>>      def fork *a, &b
>>        at_exit{ exit! }
>>        __fork__ *a, &b
>>      end
>>    end
>>    module Kernel
>>      alias_method '__fork__', 'fork'
>>      def fork *a, &b
>>        at_exit{ exit! }
>>        __fork__ *a, &b
>>      end
>>    end
>>
>> in environment.rb or something.
>
> This fixes the MySQL problem (as does manually
> disconnecting/reconnecting), but now I have another problem: popen3 just
> doesn't do anything when used within LSAPI. The program is never
> executed. Any ideas?

hmmm. no.  must be related though.  i'm staring to thinks it's lsapi which has
setup all the funky at_exit handlers, and that this is causing you grief...

> Who would have thought that simply calling an external program could be
> so difficult...

me ;-)

ultimately, in ruby queue, i had to setup a drb process before setting up db
connections.  then i used that drb process to do all forking/waiting for me.

here's another idea, try systemu, it does not use fork at all

   gem install systemu

   http://rubyforge.org/frs/?group_id=1024&release_id=7721
   http://codeforpeople.com/lib/ruby/systemu/systemu-1.0.0/README

unless you need realtime control over stdin/stdout/stderr it'll do the trick.

regards.


-a
-- 
be kind whenever possible... it is always possible.
- the dalai lama