Re: Log::Log4Perl best practices

[saintmike]

Should there be this much overhead? When I see all this repeated code, I don't like it. This adds 4 lines to each program (not a big deal) but it also adds 4 lines to each .t script (?!?!) and 2 lines to module...surely it shouldn't require this much repeated code?

Log::Log4perl can be used in different ways, just pick the one that suits you:

For simple scripts, people like using :easy mode. This approach is also discussed in this FAQ and uses

• a simplified init method without a configuration file and
• logging functions instead of objects/method calls

Here's an example:

    use Log::Log4perl qw(:easy);

    Log::Log4perl->easy_init( 
        { level   => $DEBUG,
          file    => ">>test.log" } );

    DEBUG("Debug this!");

Calling DEBUG() instead of obtaining a logger reference via get_logger($category) and then calling $logger->debug() is what Log4perl calls using stealth loggers. Stealth loggers are also recommended to be used in modules, just say

package MyPackage;
use Log::Log4perl qw(:easy);
sub method {
    DEBUG "Doing something!";
}

and you've got full-fledged logging in place. Stealth loggers use Log4perl categories equal to the current package. Performance stays the same.

The main program is responsible for calling init() or easy_init(). If it doesn't, Log::Log4perl will keep sleeping.

As for spreading like Kudzu through your application, that's a common issue with logging systems. Log::Log4perl reduces the exposure by not requiring to pass a handler around, but provides a singleton mechanism.

However, ideally, logging would be completely orthogonal to your application logic. You may have heard of aspect oriented programming (AOP), that's how it's done. Log4perl might provide a way to do that in the future.

[water]

If the modules use stealth logging,

package MyPackage;
use Log::Log4perl qw(:easy);
sub method {
    DEBUG "Doing something!";
}

How does the main driver turn debugging on an off?

use Log::Log4perl qw(:levels);
Log::Log4perl->init("/home/mycode/log4perl-conf.txt");
my $logger = Log::Log4perl->get_logger;
$logger->level($DEBUG);

is not "seen" by the module.

Or am I just not getting it by trying to set levels in my code, rather than in the conf file? I don't envision using the 'change logging level while code is running' feature, and it seems more direct to me to set the log level in the code, rather than in the conf file. I'm really just using the conf file for appender & filter specification, it seems.

Thanks for any clarification. Mike, your advice has been great, thanks.