Code Serialization and mod_perl
Hello, Please help me understand how Perl with mod_perl handles the following situation. Consider 2 clients out in the WWW using the same form to work on 2 different records of the same type. At submission, the form executes a database function and passes the data entered using the form. The function retrieves the data from the CGI-like connection, assigns the data to Perl dataspaces and begins processing the code series of the function. Now the 2nd client executes the function in the same way, right on the heels of the 1st client. In the C language in a network environment, when a client calls a database function in a DLL to access a server database, a system semaphore is is used to serialize code access to prevent the corruption ofdataspaces. With only Perl, a different Perl interpreter instance is started for each CGI request. The instances don't know about each other and dataspaces are unique to an instance. How does Perl with mod_perl handle this. Are there any important differences with the only Perl situation. Might the dataspaces be corrupted? How does this work? My technical environment is Windows XP Home, Apache 2.0.049, Perl 5.8.3, and mod_perl 2.0.2. Thank you in advance for any responses. I appreciate your time. Craig Tussey [EMAIL PROTECTED] __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Re: Code Serialization and mod_perl
On 10/5/06, Craig Tussey [EMAIL PROTECTED] wrote: Please help me understand mod_perl With only Perl, ... the instances don't know about each other and dataspaces are unique to an instance. How does mod_perl handle this. Are there any important differences with the only Perl situation. any introduction to mod_perl should tell you that some of the data may persist between request events while some is per-request. Database connections in particular may pooled and conserved. Understanding these subtleties to avoid data corruption issues such as you are legitimately concerned about is why the competent mod_perl developers can demand the big bucks. http://www.google.com/search?q=introduction+to+mod_perl is a good starting point for starting points. Have a nice day.
Re: Code Serialization and mod_perl
On Thu, 2006-10-05 at 11:56 -0700, Craig Tussey wrote: With only Perl, a different Perl interpreter instance is started for each CGI request. The instances don't know about each other and dataspaces are unique to an instance. How does Perl with mod_perl handle this. In exactly the same way. The interpreters are in separate processes or threads and share nothing. The only exception is if you run mod_perl 2 using threads and intentionally share some variables. Are there any important differences with the only Perl situation. Not in terms of separation between instances. There are issues with code that doesn't clean up after itself (e.g. using global variables instead of lexical ones) since the interpreters do not exit after each request the way they do in CGI. - Perrin
Re: Code Serialization and mod_perl
On Oct 5, 2006, at 2:56 PM, Craig Tussey wrote:
How does Perl with mod_perl handle this. Are there any
important differences with the only Perl situation.
Might the dataspaces be corrupted? How does this work?
variables will persist through every connection...
so 'use strict()' and specifically declare every variable with my /
our as appropriate
ie:
my $connected= 0;
sub connect {
my $connection= 'dbi connection';
$connected++;
return $connection
}
sub handler{
my $r= shift
if ( ! $connection ) {
$connection= connect()
}
print $connected;
}
the first time you run that, you'll call connect and increment
connected, which is local to the package. the second time though,
$connection will have been set within the handler block
and then everything that David Nicol said
