NAME Log::Dispatch::Config - Log4j for Perl SYNOPSIS use Log::Dispatch::Config; Log::Dispatch::Config->configure('/path/to/config'); my $dispatcher = Log::Dispatch::Config->instance; # or the same my $dispatcher = Log::Dispatch->instance; # or if you write your own config parser: use Log::Dispatch::Configurator::XMLSimple; my $config = Log::Dispatch::Configurator::XMLSimple->new('log.xml'); Log::Dispatch::Config->configure($config); DESCRIPTION Log::Dispatch::Config is a subclass of Log::Dispatch and provides a way to configure Log::Dispatch object with configulation file (default, in AppConfig format). I mean, this is log4j for Perl, not with all API compatibility though. METHOD This module has a class method "configure" which parses config file for later creation of the Log::Dispatch::Config singleton instance. (Actual construction of the object is done in the first "instance" call). So, what you should do is call "configure" method once in somewhere (like "startup.pl" in mod_perl), then you can get configured dispatcher instance via "Log::Dispatch::Config->instance". Formerly, "configure" method declares "instance" method in Log::Dispatch namespace. Now it inherits from Log::Dispatch, so the namespace pollution is not necessary. Currrent version still defines one-liner shortcut: sub Log::Dispatch::instance { Log::Dispatch::Config->instance } so still you can call "Log::Dispatch->instance", if you prefer, or for backward compatibility. CONFIGURATION Here is an example of the config file: dispatchers = file screen file.class = Log::Dispatch::File file.min_level = debug file.filename = /path/to/log file.mode = append file.format = [%d] [%p] %m at %F line %L%n screen.class = Log::Dispatch::Screen screen.min_level = info screen.stderr = 1 screen.format = %m In this example, config file is written in AppConfig format. See the Log::Dispatch::Configurator::AppConfig manpage for details. See the section on "PLUGGABLE CONFIGURATOR" for other config parsing scheme. GLOBAL PARAMETERS dispatchers dispatchers = file screen "dispatchers" defines logger names, which will be splitted by spaces. If this parameter is unset, no logging is done. format format = [%d] [%p] %m at %F line %L%n "format" defines log format. Possible conversions format are %d datetime string (ctime(3)) %p priority (debug, info, warning ...) %m message string %F filename %L line number %P package %n newline (\n) Note that datetime (%d) format is configurable by passing "strftime" fmt in braket after %d. (I know it looks quite messy, but its compatible with Java Log4j ;) format = [%d{%Y%m%d}] %m # datetime is now strftime "%Y%m%d" If you have Time::Piece, this module uses its "strftime" implementation, otherwise POSIX. "format" defined here would apply to all the log messages to dispatchers. This parameter is optional. See the section on "CALLER STACK" for details about package, line number and filename. PARAMETERS FOR EACH DISPATCHER Parameters for each dispatcher should be prefixed with "name.", where "name" is the name of each one, defined in global "dispatchers" parameter. You can also use ".ini" style grouping like: [foo] class = Log::Dispatch::File min_level = debug See the Log::Dispatch::Configurator::AppConfig manpage for details. class screen.class = Log::Dispatch::Screen "class" defines class name of Log::Dispatch subclasses. This parameter is essential. format screen.format = -- %m -- "format" defines log format which would be applied only to the dispatcher. Note that if you define global "format" also, %m is double formated (first global one, next each dispatcher one). This parameter is optional. (others) screen.min_level = info screen.stderr = 1 Other parameters would be passed to the each dispatcher construction. See Log::Dispatch::* manpage for the details. SINGLETON Declared "instance" method would make "Log::Dispatch::Config" class singleton, so multiple calls of "instance" will all result in returning same object. my $one = Log::Dispatch::Config->instance; my $two = Log::Dispatch::Config->instance; # same as $one See GoF Design Pattern book for Singleton Pattern. But in practice, in persistent environment like mod_perl, Singleton instance is not so useful. Log::Dispatch::Config defines "instance" method so that the object reloads itself when configuration file is modified since its last object creation time. PLUGGABLE CONFIGURATOR If you pass filename to "configure" method call, this module handles the config file with AppConfig. You can change config parsing scheme by passing another pluggable configurator object. Here is a way to declare new configurator class. The example below is hardwired version equivalent to the one above in the section on "CONFIGURATION". * Inherit from Log::Dispatch::Configurator. Stub "new" constructor is inherited, but you can roll your own with it. package Log::Dispatch::Configurator::Hardwired; use base qw(Log::Dispatch::Configurator); sub new { bless {}, shift; } * Implement two required object methods "get_attrs_global" and "get_attrs". "get_attrs_global" should return hash reference of global parameters. "dispatchers" should be an array reference of names of dispatchers. sub get_attrs_global { my $self = shift; return { 'format' => undef, dispatchers => [ qw(file screen) ], }; } "get_attrs" accepts name of a dispatcher and should return hash reference of parameters associated with the dispatcher. sub get_attrs { my($self, $name) = @_; if ($name eq 'file') { return { class => 'Log::Dispatch::File', min_level => 'debug', filename => '/path/to/log', mode => 'append', 'format' => '[%d] [%p] %m at %F line %L%n', }; } elsif ($name eq 'screen') { return { class => 'Log::Dispatch::Screen', min_level => 'info', stderr => 1, 'format' => '%m', }; } else { die "invalid dispatcher name: $name"; } } * Implement optional "needs_reload" and "reload" methods. "needs_reload" accepts Log::Dispatch::Config instance and should return boolean value if the object is stale and needs reloading itself. Stub config file mtime based "needs_reload" method is declared in Log::Dispatch::Configurator as below, so if your config class is based on filesystem files, you do not need to reimplement this. sub needs_reload { my($self, $obj) = @_; return $obj->{ctime} < (stat($self->{file}))[9]; } If you do not need *singleton-ness*, always return true. sub needs_reload { 1 } "reload" method is called when "needs_reload" returns true, and should return new Configurator instance. Typically you should place configuration parsing again on this method, so Log::Dispatch::Configurator again declares stub "reload" method that clones your object. sub reload { my $self = shift; my $class = ref $self; return $class->new($self->{file}); } * That's all. Now you can plug your own configurator (Hardwired) into Log::Dispatch::Config. What you should do is to pass configurator object to "configure" method call instead of config file name. use Log::Dispatch; use Log::Dispatch::Configurator::Hardwired; my $config = Log::Dispatch::Configurator::Hardwired->new; Log::Dispatch::Config->configure($config); CALLER STACK When you call logging method from your subroutines / methods, caller stack would increase and thus you can't see where the log really comes from. package Logger; my $Logger = Log::Dispatch::Config->instance; sub logit { my($class, $level, $msg) = @_; $Logger->$level($msg); } package main; Logger->logit('debug', 'foobar'); You can adjust package variable $Log::Dispatch::Config::CallerDepth to change the caller stack depth. The default value is 3, (which depends heavily on Log::Dispatch's undocumented implementation. It might be changed in future). sub logit { my($class, $level, $msg) = @_; local $Log::Dispatch::Config::CallerDepth = 4; $Logger->$level($msg); } AUTHOR Tatsuhiko Miyagawa with much help from Matt Sergeant . This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. SEE ALSO the Log::Dispatch::Configurator::AppConfig manpage, the Log::Dispatch manpage, the AppConfig manpage