[log4perl-devel] Design question: Why doesn't Log::Log4Perl descend from Class::Singleton?

[Craig M. <C.M...@of...>]

Hi,

Looking at the Log::Log4Perl code and it's suitability to be used in an
application framework I'm working on, I see that it can't be used
(safely) in multiple applications running within the same mod_perl
server. This is because even though these applications use there own
module namespaces, they obviously will clash with each other when
calling the init or init_once method.=20

I think a better design would be to make Log::Log4Perl descend from
Class::Singleton, store all variables that are now globals in the
instance, and let users optionally create subclassed versions of
Log::Log4Perl in there own namespaces.

E.g. you'ld get something like this:

=20

package AppX;

use AppX::Log4Perl; # descends from Log::Log4Perl

...

my $l4p =3D AppX::Log4Perl->instance();

$l4p->init_once('appx.conf');

my $logger =3D $l4p->get_logger();

=20

.... then in another application sharing the same httpd:

package AppY;

use AppY::Log4Perl; # descends from Log::Log4Perl

...

$l4p->init_once('appy.conf');

my $logger =3D $l4p->get_logger();

=20

=20

... and AppX::Log4Perl will look like exactly like this:

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package AppX::Log4Perl;

use strict;

use base(Log::Log4Perl);

1;

__END__

=20

=20

I know it will be a major change to build this into Log::Log4Perl but I
think it can be done while retaining backwards compatibility.

All current class methods now can be automatically turned into both
class and object methods at the same time like this:

sub a_class_method {

 my $proto =3D shift;

 my $self =3D ref($proto)  ? $proto : $proto->instance();

 }

Actually the magic above can become more involved if necessary.

=20

Log::Log4Perl is a great piece of work.... I only miss that.

=20

In general when making packages, one must really scratch one's head a
few times if deciding to use globals, because they are almost always
unnecessary (except for constants) and a simple object or else
Class::Singleton based alternative is almost always the solution.

=20

That's just my 2p.

=20

Regards,

Craig Manley.