Why do variables retain their values between requests?
Unless scoped by my() or local(), perl variables in mod_perl
are treated as globals, and values set may persist from one
request to another. This can be seen in as simple a script
as this:
<HTML><BODY>
$counter++;
$Response->Write("<BR>Counter: $counter");
</BODY></HTML>
The value for $counter++ will remain between requests.
Generally use of globals in this way is a BAD IDEA,
and you can spare yourself many headaches if do
"use strict" perl programming which forces you to
explicity declare globals like:
use vars qw($counter);
You can make all your Apache::ASP scripts strict by
default by setting:
PerlSetVar UseStrict 1
Apache errors on the PerlHandler or PerlModule directives ?
You get an error message like this:
Invalid command 'PerlModule', perhaps mis-spelled or defined by a
module not included in the server configuration.
You do not have mod_perl correctly installed for Apache. The PerlHandler
and PerlModule directives in Apache *.conf files are extensions enabled by mod_perl
and will not work if mod_perl is not correctly installed.
Common user errors are not doing a 'make install' for mod_perl, which
installs the perl side of mod_perl, and not starting the right httpd
after building it. The latter often occurs when you have an old apache
server without mod_perl, and you have built a new one without copying
over to its proper location.
To get mod_perl, go to http://perl.apache.org
Error: no request object (Apache=SCALAR(0x???????):)
Your Apache + mod_perl build is not working properly,
and is likely a RedHat Linux RPM DSO build. Make sure
you statically build your Apache + mod_perl httpd,
recompiled fresh from the sources.
I am getting a tie or MLDBM / state error message, what do I do?
Make sure the web server or you have write access to the eg directory,
or to the directory specified as Global in the config you are using.
Default for Global is the directory the script is in (e.g. '.'), but should
be set to some directory not under the www server document root,
for security reasons, on a production site.
Usually a
chmod -R -0777 eg
will take care of the write access issue for initial testing purposes.
Failing write access being the problem, try upgrading your version
of Data::Dumper and MLDBM, which are the modules used to write the
state files.
Sessions
How can I use $Session to store complex data structures.
Very carefully. Please read the $Session documentation in
the OBJECTS section. You can store very complex objects
in $Session, but you have to understand the limits, and
the syntax that must be used to make this happen.
In particular, stay away from statements that that have
more than one level of indirection on the left side of
an assignment like:
BAD: $Session->{complex}{object} = $data;
How can I keep search engine spiders from killing the session manager?
If you want to disallow session creation for certain non web
browser user agents, like search engine spiders, you can use a mod_perl
PerlInitHandler like this to set configuration variables at runtime:
# put the following code into httpd.conf and stop/start apache server
PerlInitHandler My::InitHandler
<Perl>
package My::InitHandler;
use Apache;
sub handler {
my $r = shift; # get the Apache request object
# if not a Mozilla User Agent, then disable sessions explicitly
unless($r->headers_in('User-Agent') =~ /^Mozilla/) {
$r->dir_config('AllowSessionState', 'Off');
}
return 200; # return OK mod_perl status code
}
1;
</Perl>
This will configure your environment before Apache::ASP executes
and sees the configuration settings. You can use the mod_perl
API in this way to configure Apache::ASP at runtime.
Note that the Session Manager is very robust on its own, and denial
of service attacks of the types that spiders and other web bots
normally execute are not likely to affect the Session Manager significantly.
How can I use $Session to store a $dbh database handle ?
You cannot use $Session to store a $dbh handle. This can
be awkward for those coming from the IIS/NT world, where
you could store just about anything in $Session, but this
boils down to a difference between threads vs. processes.
Database handles often have per process file handles open,
which cannot be shared between requests, so though you
have stored the $dbh data in $Session, all the other
initializations are not relevant in another httpd process.
All is not lost! Apache::DBI can be used to cache
database connections on a per process basis, and will
work for most cases.
Development
VBScript or JScript supported?
Only Perl scripting is supported with this module.
How is database connectivity handled?
Database connectivity is handled through perl's DBI & DBD interfaces.
In the UNIX world, it seems most databases have cross platform support in perl.
You can find the book on DBI programming at http://www.oreilly.com/catalog/perldbi/
DBD::ODBC is often your ticket on Win32. On UNIX, commercial vendors
like OpenLink Software (http://www.openlinksw.com/) provide the nuts and
bolts for ODBC.
Database connections can be cached per process with Apache::DBI.
What is the best way to debug an ASP application ?
There are lots of perl-ish tricks to make your life developing
and debugging an ASP application easier. For starters,
you will find some helpful hints by reading the
$Response->Debug() API extension, and the Debug
configuration directive.
How are file uploads handled?
Please see the CGI section. File uploads are implemented
through CGI.pm which is loaded at runtime only for this purpose.
This is the only time that CGI.pm will be loaded by Apache::ASP,
which implements all other cgi-ish functionality natively. The
rationale for not implementing file uploads natively is that
the extra 100K in memory for CGI.pm shouldn't be a big deal if you
are working with bulky file uploads.
How do I access the ASP Objects in general?
All the ASP objects can be referenced through the main package with
the following notation:
$main::Response->Write("html output");
This notation can be used from anywhere in perl, including routines
registered with $Server->RegisterCleanup().
You use the normal notation in your scripts, includes, and global.asa:
$Response->Write("html output");
Can I print() in ASP?
Yes. You can print() from anywhere in an ASP script as it aliases
to the $Response->Write() method. Using print() is portable with
PerlScript when using Win32::ASP in that environment.
Do I have access to ActiveX objects?
Only under Win32 will developers have access to ActiveX objects through
the perl Win32::OLE interface. This will remain true until there
are free COM ports to the UNIX world. At this time, there is no ActiveX
for the UNIX world.
Support and Production
How do I get things I want done?!
If you find a problem with the module, or would like a feature added,
please mail support, as listed in the SUPPORT section, and your
needs will be promptly and seriously considered, then implemented.
What is the state of Apache::ASP? Can I publish a web site on it?
Apache::ASP has been production ready since v.02. Work being done
on the module is on a per need basis, with the goal being to eventually
have the ASP API completed, with full portability to ActiveState PerlScript
and MKS PScript. If you can suggest any changes to facilitate these
goals, your comments are welcome.
