Re: Inversion of control: logging and configuration

Couple of Log::Log4perl's best practices:

Call Log::Log4perl->init once, in the main script, not in any module you're using.
I'm not sure why you're using AppConfig on top of that, this way, you're giving up on useful functionality like init_and_watch. The most common usage of init() is passing it the name of a Log4perl configuration file.

In your modules, use

    # Foo.pm
    package Foo;
    use Log::Log4perl qw(:easy);
    sub foo {
        DEBUG "Fooing the database";
    }
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In your Log4perl config file (read in by the main script, not the module, via ->init($cfg_file)), you're telling which modules you want logging enabled in:

    # l4p.conf

    # Where should logging be enabled? 
    log4perl.category.Foo              = DEBUG, Logfile
    log4perl.category.Bar              = DEBUG, Logfile

    # Appenders
    log4perl.appender.Logfile          = Log::Log4perl::Appender::File
    log4perl.appender.Logfile.filename = test.log
    log4perl.appender.Logfile.layout   = Log::Log4perl::Layout::Simple
+Layout
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If the main program doesn't call init(), the Log4perl statements in Foo.pm will be dormant.
If the main script calls init(), logging will be active. This doesn't necessarily mean Foo will be generating output, from the central config file, you will be able to control the amount of logging for each individual module separately (or alltogether, if you like to).

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