Re^2: mod_perl and multiuser global variables

Replies are listed 'Best First'.
Re^3: mod_perl and multiuser global variables by wazzuteke (Hermit) on Dec 05, 2005 at 15:51 UTC
This is somewhat of a tricky question. Assuming you're running Apache on *nix, each child will be forked off into it's own process. Therefore, if you make a variable global, it will only be global to that child. However, if you make the same variable name global in each child to the same value (via a database, or something similar), then you will have some sort of psudo-global variable. Nonetheless, to have a variable that is global to the Parent and each child is not possible; at least from my knowledge of mod_perl and Apache (someone correct me if I'm wrong here). ---hA\|\|ta---- `print map{$_.' '}grep{/\w+/}@{[reverse(qw{Perl Code})]} or die while ( 'trying' );`	[reply] [d/l]
Re^4: mod_perl and multiuser global variables by maverick (Curate) on Dec 05, 2005 at 16:14 UTC
You can use "global" in memory values, but only as constants. Once you change the value in one place, it only changes there. There's a couple of ways you can make read-write globals. Via a database (as mentioned above), via a second instance of Apache::Session (or CGI::Session) using a constant superLongSecretKeyThatDoesn'tFitTheAutoGenerateFormatKey (ahem) or something like IPC::ShareLite to get true "shared across all children" global variables. The Database method might have some performance penalties, but the advantage is that if you every start load balancing web servers, your global variables are still global. The Secret Session method, is probably the fastest and easiest to code, since you already have similar parts in your program, but it also has some security implications surrounding your secret session key. The IPC::SharedLite method requires installing a new module and learning some new (but realively straight forward) techniques. The amount of "shared" memory on a system is much smaller than "main" memory (at least with Unix) so you can't cram it TOO full, but it will yield the desired effect. For what you're trying to do, I'd be tempted to pick this method. /\/\averick	[reply]
Re^4: mod_perl and multiuser global variables by rsennat (Beadle) on Dec 05, 2005 at 15:56 UTC
Probably that should be right. But then whats the way to override this problem?? And i just got a thought here, even after using CGI::Session, i will read the user id from the session stored and store it in a variable in that .cgi file. Anyways it becomes a global var. So how do i use it to maintain a persistent data. thanks	[reply]
Re^5: mod_perl and multiuser global variables by Moron (Curate) on Dec 05, 2005 at 16:56 UTC
You need to manage the multi-user session info in a Storable. I couldn't find a CGI::Session::Driver::Storable, but it should be easy enough to write interface routines between CGI::Session::Driver and Storable. The latter has advisory locking routines which will be needed when updating the storable in the multi-session scenario. -M Free your mind	[reply]