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

[prev] [thread] [next] [Date index for 2004/11/30]

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...

What about the solution of ithreads? Originally ithreads were storing 
their context in ThreadLocalStorage, and this didn't work under mp2, so it 
was rewritten to store the context in a perl PL_ interpreter global, now 
ithreads can be run inside the same thread.

Could the same solution be applied for COM context? Make it independent 
from threads?

> It looks like "thread-safety" has a whole range of meanings in the
> ithreads world. :(

:(

        -- 
        __________________________________________________________________
Stas Bekman            JAm_pH ------> Just Another mod_perl Hacker
http://stason.org/     mod_perl Guide ---> http://perl.apache.org
mailto:stas@xxxxxx.xxx http://use.perl.org http://apacheweek.com
http://modperlbook.org http://apache.org   http://ticketmaster.com

-- 
Report problems: http://perl.apache.org/bugs/
Mail list info: http://perl.apache.org/maillist/modperl.html
List etiquette: http://perl.apache.org/maillist/email-etiquette.html