man Poet::Log (3): Poet logging

SYNOPSIS

# In a conf file...
log:
defaults:
level: info
output: poet.log
layout: "%d{dd/MMM/yyyy:HH:mm:ss.SS} [%p] %c - %m - %F:%L - %P%n"
class:
CHI:
level: debug
output: chi.log
layout: "%d{dd/MMM/yyyy:HH:mm:ss.SS} %m - %P%n"
MyApp::Foo:
output: stdout
# In a script...
use Poet::Script qw($log);
# In a module...
use Poet qw($log);
# In a component...
my $log = $m->log;
# For an arbitrary category...
my $log = Poet::Log->get_logger(category => 'MyApp::Bar');
# then...
$log->error("an error occurred");
$log->debugf("arguments are: %s", \@_)
if $log->is_debug();

DESCRIPTION

Poet uses Log::Any and Log::Log4perl for logging, with simplified configuration for the common case.

Log::Any is a logging abstraction that allows CPAN modules to log without knowing about which logging framework is in use. It supports standard logging methods ("$log->debug", "$log->is_debug") along with sprintf variants ("$log->debugf").

Log4perl is a powerful logging package that provides just about any logging-related feature you'd want. One of its only drawbacks is its somewhat cumbersome configuration. So, we provide a way to configure Log4perl simply through Poet configuration if you just want common features.

Note: Log4perl is not a strict dependency for Poet. Log messages will simply not get logged until you install it or until you modify logging for your app.

CONFIGURATION

The configurations below can go in any Poet conf file, e.g. "local.cfg" or "global/log.cfg".

Here's a simple configuration that caches everything to "logs/poet.log" at "info" level. This is also the default if no configuration is present.

    log:
      defaults:
        level: info
        output: poet.log
        layout: %d{dd/MMM/yyyy:HH:mm:ss.SS} [%p] %c - %m - %F:%L - %P%n

Here's a more involved configuration that maintains the same default, but adds several categories that are logged differently:

    log:
      defaults:
        level: info
        output: poet.log
        layout: "%d{dd/MMM/yyyy:HH:mm:ss.SS} [%p] %c - %m - %F:%L - %P%n"
      category:
        CHI:
          level: debug
          output: chi.log
          layout: "%d{dd/MMM/yyyy:HH:mm:ss.SS} %m - %P%n"
        MyApp::Foo:
          output: stdout

For the default and for each category, you can specify three different settings:

level - one of the valid log4perl levels (fatal, error, warn, info, debug, trace)
output - can be a relative filename (which will be placed in the Poet log directory), an absolute filename, or the special names ``stdout'' or ``stderr''
layout - a valid log4perl PatternLayout string.

If a setting isn't defined for a specific category then it falls back to the default. In this example, "MyApp::Foo" will inherit the default level and layout.

Notice that we use '::' instead of '.' to specify hierarchical category names, because '.' would interfere with Poet::Conf dot notation.

Finally, if you must use a full Log4perl configuration file, you can specify it this way:

    log:
      log4perl_conf: /path/to/log4perl.conf

USAGE

Obtaining log handle

In a script (log category will be 'main'):
```
    use Poet::Script qw($log);
```
In a module "MyApp::Foo" (log category will be 'MyApp::Foo'):
```
    use Poet qw($log);
```
In a component "/foo/bar" (log category will be 'Mason::Component::foo::bar'):
```
    my $log = $m->log;
```

Manually for an arbitrary log category:

    my $log = Poet::Log->get_logger(category => 'Some::Category');
        
    # or
    
    my $log = MyApp::Log->get_logger(category => 'Some::Category');

Using log handle

    $log->error("an error occurred");
    $log->debugf("arguments are: %s", \@_)
        if $log->is_debug();

See "Log::Any|Log::Any" for more details.

MODIFIABLE METHODS

These methods are not intended to be called externally, but may be useful to override or modify with method modifiers in subclasses. Their APIs will be kept as stable as possible.

initialize_logging: Called once when the Poet environment is initialized. By default, initializes log4perl with the results of ``generate_log4perl_config'' and then calls "Log::Any::Adapter->set('Log4perl')". You can modify this to initialize log4perl in your own way, or use a different Log::Any adapter, or use a completely different logging system.
generate_log4perl_config: Returns a log4perl config string based on Poet configuration. You can modify this to construct and return your own config.

AUTHOR

Jonathan Swartz <[email protected]>

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.