Andrew,
Also check out IPC::Shareable.
This allows you to tie variables to shared memory segments and allow for
safe concurrant access.
You can use Apache::Session to maintain state information across all child
processes as well. If you use the Apache::Session::IPC then you're going to
be using a fairly consistent access mechanism to your tied variables if you
decide you also want to have regular user sessions too (ie/
Apache::Session::File or other).
Jay
----- Original Message -----
From: "Andrew Ho" <[EMAIL PROTECTED]>
To: "mod_perl List" <[EMAIL PROTECTED]>
Sent: Saturday, March 31, 2001 1:00 AM
Subject: Re: Shared memory between child processes
> Hello,
>
> RR>I'm needing to implement a handler that uses a true Singleton pattern
for
> RR>the class instance. One per server, not just one per process (or
thread).
>
> SL>You'll need to use some form of persistance mechanism such as a
> SL>database, file, or perhaps (assuming you're on a Unix system)
> SL>something like System V shared memory or semaphores.
>
> You can find more information on maintaining server-side state in the
> mod_perl guide or from the mod_perl book (at perl.apache.org and
> www.modperl.com, respectively).
>
> SL>One quick 'n cheap way to implement mutual exclusion between Unix
> SL>processes (executing on the same processor) is to use mkdir, which is
> SL>atomic (ie once a process requests a mkdir, the mkdir will either be
> SL>done or rejected before the requesting process is preempted by any
> SL>other process).
>
> IMO, this is sort of cumbersome; on a single processor, you can just use
> advisory file locking. It's when you get onto NFS mounted systems with
> high concurrency that you have to muck with rolling your own mutexes (I
> find I usually use atomic move for that purpose). But on a single system,
> use flock() and a known lockfile, or sysopen with O_CREAT|O_EXCL if you
> can't put the file there beforehand.
>
> Humbly,
>
> Andrew
>
> ----------------------------------------------------------------------
> Andrew Ho http://www.tellme.com/ [EMAIL PROTECTED]
> Engineer [EMAIL PROTECTED] Voice 650-930-9062
> Tellme Networks, Inc. 1-800-555-TELL Fax 650-930-9101
> ----------------------------------------------------------------------
>
>
