hi,
you can't specify a base address on Apache because portability and
compatibilty with different other softs. And that way will not fix
this problem.
you can load and manage a shared map in Apache but you can't expand
it. That problem is due in part to the Apache MPM prefork/worker engine.
PostGreSQL doesn't have the same problem because it doesn't have to
interrupt some CGI or exec programs . For example actualy PHP can't
work on threaded environnement because its global variables and note
that its parser isn't atomic. these problems are also present with
Perl, Tomcat etc...
i had work for a long time about this subject and the only way i have
found it's to build a new SHM inter-process protocol associated with
a new MPM engine.
it's a design problem and Apache isn't the person in charge. They can
done what i say but it's little nightmare.
also note that mod_auth_ldap is experimental in Apache.
- michael
Le 16 nov. 05 à 12:09, Vadim Chekan a écrit :
Some time ago I reported a reason why Ldap module can not work on
Windows and crashes when caching is enabled. It is because shared
memory that is obtained by processes has different base address for
each process.
I thought to replace pointers with offsets everywhere but it became
really ugly. To get any pointer you have to make a function and call
it.
This made me thinking how projects like PostgreSQL which recently has
been ported to Win32 and are very shared memory oriented did it. As a
result I found that there is a function in Win API that allows to map
shared memory with desired base address!
Currently APR uses Win32 API MapViewOfFile(). But there is a
modification of this function, MapViewOfFileEx()
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/
fileio/fs/mapviewoffileex.asp
which has an additional argument
================================
lpBaseAddress
[in] A pointer to the memory address in the calling process
address space where mapping begins.
...
If lpBaseAddress is NULL, the operating system chooses the mapping
address. In this scenario, the function is equivalent to the
MapViewOfFile function.
================================
So, I'm quite sure APR needs to use this function to map shared memory
to the same address in all processes and make win application similar
to unix.
Vadim Chekan.
