Re: Apache2/Modperl2 fails to preload Win32::OLE at server startup

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Hello all
the discussion has become a little bit technical for me...

What I understand is that I've been lucky to make this work so far and that 
sooner or later I will end up with some problems.

Is there some not-too-complicated way to workaround the problems in the perl 
scripts or at least prevent the most severe problems to happen?

NOTE: Actually what I'm currently doing is a authentication handler derived from 
Apache::AuthCookie. My handler is connecting to a database through Win32::OLE to 
authenticate users. Active connections are kept in a cache until users logout.
 From what I understand of Jan's answer: should I keep an active connection per 
thread-id?

Jan Dubois wrote:
> On Mon, 29 Nov 2004, Stas Bekman wrote:
> 
>>If you just call perl_clone it runs in the new perl context, but
>>inside the same thread. At least on Unix. Under ithreads.pm it
>>probably starts a new thread first (but I'm not sure). Under
>>modperl 2, there is no 1:1 relationship between interpreters and
>>apache threads
>>
>>so that means that it's out of question that Win32::OLE can be used at
>>all, right? I suppose Thierry was just lucky to get the thing working
>>by loading at request time, and most likely under a bit of stress
>>testing it'll show the same problems.
> 
> 
> Yes, it sounds like COM and mod_perl threads won't mix.  Even if Win32::OLE
> was made thread-safe (I still have that on my todo list), it would probably
> not work with mod_perl 2.0 because COM objects have apartment affinity.  You
> can't just create a COM object in one thread and then use it from another.
> 
> It will have to be explicitly marshaled in case the different threads
> belong to different threading apartments. This means COM will create a
> proxy object in the calling thread and uses something like in-process
> RPC to execute the call in the "home-thread" of the real object.
> 
> I guess this can be worked around too, by storing the "owning" thread id
> in each Win32::OLE object and then explicitly requesting it to be
> marshaled if it is being used from a different thread. But that will
> only work if both threads will properly crank the Windows message loop,
> in case one of the threads belongs to a single threaded apartment. It
> becomes a big can of worms...
> 
> It looks like "thread-safety" has a whole range of meanings in the
> ithreads world. :(
> 
> Cheers,
> -Jan
> 
> 


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Thierry Valentin
earth decision sciences SA
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