Re: shared memory

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Perrin Harkins wrote:
> On Tue, 2005-03-15 at 23:26 +0100, André Warnier wrote:
> 
>>Do I get the feeling this is getting a bit off-topic ? :-)
> 
> 
> That's because we believe we answered your question and are now talking
> about interesting side-topics.
> 
> 
>>a) is it possible/easy to share this data between a number of 
>>Apache2/mod_perl2 request handlers ? If yes, how ?
> 
> 
> BerkeleyDB, MySQL, or SQLite3, but I don't think BDB works in Win32.  I
> don't think any of the shared memory modules work on Win32 either, and
> they tend to be slower than MySQL anyway, for various reasons.
> 
Thank you.  Now you did indeed.
Pardon my insistence.  I undertand I am the one looking for help, and 
that you are kind enough to offer it, and I am grateful.

I have previously gone though a lot of perl and mod_perl documentation, 
and perl module descriptions, and I never seemed to find a clear answer 
about wether yes or no it was possible to share in-memory data between 2 
perl processes (or threads) running under Apache.
There are lots of discussions and explanations about children and 
threads and forking and copy-on-write and SV's and so on, but nothing 
very clear for a simple mind like mine.
I understand from all that information, that it is not an easy thing to 
do, specially under OS'es as different as Unix and Windows, with perl 
not really separating data and code and so on.

I guess what you answer above means "no, there isn't".

What I am wondering about is this : such a possibility of sharing a 
memory area seems like something rather desirable under some 
circumstances.  At least I have seen several messages on that very 
topic, in this list and other places.
On the other hand, mod_perl seems to have some deep interactions with 
the innards of the Apache server, for example direct manipulation of the 
"bucket brigades".  How come no-one has come up yet with some scheme to 
"hijack" one of these bucket brigades (or some other internal Apache 
memory area) to provide such a capability ?

Also, for instance, the DBI module and it's companion Apache::DBI 
provide persistent connections to databases. And to my knowledge, they 
are available under Unix as well as Windows.  For doing this, there must 
be some form of memory sharing at work, isn't it so ?

André Warnier