SYNOPSIS

In your config.yml

   logger: log4perl
   log: core
   log4perl:
      config_file: log4perl.conf

In your log4perl.conf

   log4perl.rootLogger              = DEBUG, LOG1
   log4perl.appender.LOG1           = Log::Log4perl::Appender::File
   log4perl.appender.LOG1.filename  = /var/log/mylog.log
   log4perl.appender.LOG1.mode      = append
   log4perl.appender.LOG1.layout    = Log::Log4perl::Layout::PatternLayout
   log4perl.appender.LOG1.layout.ConversionPattern = %d %p %m %n

DESCRIPTION

This class is an interface between Dancer's logging engine abstraction layer and the Log::Log4perl library. In order to use it, you have to set the "logger" engine to "log4perl".

You can use either Log::Log4perl or Log::Log4perl::Tiny. If you want to use the latter, just specify the "tiny" option in the specific configuration.

You can decide to let the module perform the initialisation of the logging system, or you can do it by yourself. In the latter case, you can pass the "no_init" parameter, which instructs the module not to perform the initialisation.

After initialisation, you can decide to use Dancer's functions or the ones provided by either Log::Log4perl or Log::Log4perl::Tiny, e.g. the stealth loggers in case of a simplified interface.

Note that Dancer's "log" and "logger_format" options are still honored, which means you need to be aware of the following:

"logger_format" is still processed and becomes %m in Log4perl's format placeholders. This allows you to pass Dancer placeholders that aren't available as Log4perl placeholders.

Dancer's "core" level messages are passed to Log4perl as level "trace" but will not be passed unless Dancer's "log" config is "core".

"log" should be set a lower priority than the lowest priority as set in your Log4perl configuration. If it isn't, Dancer::Logger::Abstract will not pass the message to Log4perl.

CONFIGURATION

The configuration capabilities vary depending on the underlying library you have, even though the following configurations are common:

no_init: skip the initialisation phase of the logging module, assuming that it is performed elsewhere.
tiny: allows you to decide whether Log::Log4perl (when set to a false value) or Log::Log4perl::Tiny (when set to a true value) should be used.

Log::Log4perl

If you're using standard Log::Log4perl, then you have two alternatives to pass a configuration:

config_file

via a configuration file, using the "config_file" option:

   logger: log4perl
   log4perl:
      config_file: log4perl.conf

config

via a straight configuration text, using the "config" option:

   logger: log4perl
   log4perl:
      config: |
         log4perl.rootLogger              = DEBUG, LOG1
         log4perl.appender.LOG1           = Log::Log4perl::Appender::File
         log4perl.appender.LOG1.filename  = /var/log/mylog.log
         log4perl.appender.LOG1.mode      = append
         log4perl.appender.LOG1.layout    = Log::Log4perl::Layout::PatternLayout
         log4perl.appender.LOG1.layout.ConversionPattern = %d %p %m %n

Log::Log4perl::Tiny

If all you have is Log::Log4perl::Tiny, you can set some parameters:

level

the log "level"

   logger: log4perl
   log4perl:
      tiny: 1
      level: INFO

format

the log "format" (aliased to "layout" as well)

   logger: log4perl
   log4perl:
      tiny: 1
      format: [%p] %m%n

EXAMPLES

All examples below assume that you have your Log::Log4perl initialisation stuff inside a file called log4perl.conf, e.g. something along the following lines:

   log4perl.logger = INFO, Screen
   log4perl.appender.Screen = Log::Log4perl::Appender::Screen
   log4perl.appender.Screen.stderr = 1
   log4perl.appender.Screen.stdout = 0
   log4perl.appender.Screen.layout = Log::Log4perl::Layout::PatternLayout
   log4perl.appender.Screen.layout.ConversionPattern = [%d] [%-5p] %m%n

The above initialisation text is actually what you get by default.

Log::Log4perl, Automatic Initialisation, Dancer Logging Interface

In this case you'll probably want to let the module handle the initialisation and forget about Log::Log4perl in your code. In the Dancer configuration file:

   # config.yml
   logger: log4perl
   log: info
   log4perl:
      config_file: log4perl.conf

In your code:

   # somewhere...
   get '/please/warn' => sub {
      warning "ouch!"; # good ol' Dancer warning
      return ':-)';
   };

Log::Log4perl, Manual Initialisation, Log::Log4perl Stealth Interface

If you want to use Log::Log4perl's stealth interface, chances are you also want to avoid a full configuration file and rely upon "easy_init()". In this case, you will probably want to perform the initialisation by your own, so your configuration file will be bare bones:

   # config.yml
   logger: log4perl
   log: info
   log4perl:
      no_init: 1

and your code will contain all the meat:

   use Log::Log4perl qw( :easy );
   Log::Log4perl->easy_init($INFO);
   get '/please/warn' => sub {
      WARN 'ouch!'; # Log::Log4perl way of warning
      return ';-)';
   };

Log::Log4perl, Whatever Initialisation, Whatever Interface

Whatever the method you use to initialise the logger (but take care to initialise it once and only once, see Log::Log4perl), you can always use both Dancer and Log::Log4perl functions:

   use Log::Log4perl qw( :easy );
   get '/please/warn/2/times' => sub {
      warning 'ouch!'; # Dancer style
      WARN    'OUCH!'; # Log::Log4perl style
      return ':-D';
   };

If you don't like either functional interface, and prefer to stick to Log::Log4perl's object-oriented interface to avoid collisions in function names:

   use Log::Log4perl ();
   get '/please/warn/2/times' => sub {
      get_logger()->warn('ouch!'); # Log::Log4perl, OO way
      return 'B-)';
   };

Well, you get the idea... just peruse Log::Log4perl documentation for more!

Log::Log4perl::Tiny, Automatic Initialisation, Any Interface

If you prefer to use Log::Log4perl::Tiny you can put the relevant options directly inside the configuration file:

   # config.yml
   logger: log4perl
   log: debug
   log4perl:
      tiny: 1
      level: DEBUG
      format:  [%p] %m%n

At this point, you can import the relevant methods in your code and use them as you would with Log::Log4perl:

   use Log::Log4perl::Tiny qw( :easy );
   get '/please/warn' => sub {
      WARN 'ouch!'; # Log::Log4perl(::Tiny) way of warning
      # you can also use Dancer's warning here...
      warning 'OUCH!';
      return ';-)';
   };

Log::Log4perl::Tiny, Any Initialisation, Any Interface

As an alternative to the previous example, you can also limit the configuration file to a minimum:

   # config.yml
   logger: log4perl
   log: info
   log4perl:
      tiny: 1

and initialise the logging library inside the code:

   use Log::Log4perl::Tiny qw( :easy );
   Log::Log4perl->easy_init($INFO);
   get '/please/warn' => sub {
      WARN 'ouch!'; # Log::Log4perl(::Tiny) way of warning
      # you can also use Dancer's warning here...
      warning 'OUCH!';
      return ';-)';
   };

SUPPORT

If you find a bug, have a comment or (constructive) criticism you have different options:

just write to the "AUTHOR"
open a bug request on the relevant RT queue at https://rt.cpan.org/Public/Dist/Display.html?Name=Dancer-Logger-Log4perl
open an issue or propose a patch on GitHub at https://github.com/polettix/Dancer-Logger-Log4perl