Log/Dispatch/Config.pm

package Log::Dispatch::Config;

use strict;
use vars qw($VERSION);
$VERSION = 1.02;

use Log::Dispatch 2.00;
use base qw(Log::Dispatch);

# caller depth: can be changed from outside
$Log::Dispatch::Config::CallerDepth = 0;

sub _croak { require Carp; Carp::croak(@_); }

# accessor for symblic reference
sub __instance {
    my $class = shift;
    no strict 'refs';
    my $instance = "$class\::_instance";
    $$instance = shift if @_;
    return $$instance;
}

sub _configurator_for {
    my($class, $stuff) = @_;
    return $stuff if UNIVERSAL::isa($stuff, 'Log::Dispatch::Configurator');
    require Log::Dispatch::Configurator::AppConfig;
    return Log::Dispatch::Configurator::AppConfig->new($stuff);
}

sub configure {
    my($class, $stuff) = @_;
    _croak "no config file or configurator supplied" unless $stuff;
    my $config = $class->_configurator_for($stuff);
    $config->myinit;
    $class->__instance($config);
}

sub configure_and_watch {
    my $class = shift;
    $class->configure(@_);
    $class->__instance->should_watch(1); # tells conf to watch config file
}

# backward compatibility
sub Log::Dispatch::instance { __PACKAGE__->instance; }

sub instance {
    my $class = shift;

    my $instance = $class->__instance or _croak "configure not yet called.";
    if ($instance->isa('Log::Dispatch::Config')) {
        # reload singleton on the fly
        $class->reload if $instance->needs_reload;
    }
    else {
        # first time call: $_instance is L::D::Configurator::*
        $class->__instance($class->create_instance($instance));
    }
    return $class->__instance;
}

sub needs_reload {
    my $self = shift;
    return $self->{config}->should_watch && $self->{config}->needs_reload;
}

sub reload {
    my $proto = shift;
    my $class = ref $proto || $proto;
    my $instance = $class->__instance;
    $instance->{config}->reload;
    $class->__instance($class->create_instance($instance->{config}));
}

sub create_instance {
    my($class, $config) = @_;
    $config->{LDC_ctime} = time;        # creation time

    my $global = $config->get_attrs_global;
    my $callback = $class->format_to_cb($global->{format}, 0);
    my %dispatchers;
    foreach my $disp (@{$global->{dispatchers}}) {
        $dispatchers{$disp} = $class->config_dispatcher(
            $disp, $config->get_attrs($disp),
        );
    }
    my %args;
    $args{callbacks} = $callback if defined $callback;
    my $instance = $class->new(%args);

    for my $dispname (keys %dispatchers) {
        my $logclass = delete $dispatchers{$dispname}->{class};
        $instance->add(
            $logclass->new(
                name => $dispname,
                %{$dispatchers{$dispname}},
            ),
        );
    }

    $instance->{config} = $config;
    return $instance;
}

sub config_dispatcher {
    my($class, $disp, $var) = @_;

    my $dispclass = $var->{class} or _croak "class param missing for $disp";

    eval qq{require $dispclass};
    _croak $@ if $@ && $@ !~ /locate/;

    if (exists $var->{format}) {
        $var->{callbacks} = $class->format_to_cb(delete $var->{format}, 2);
    }
    return $var;
}

sub format_to_cb {
    my($class, $format, $stack) = @_;
    return undef unless defined $format;

    # caller() called only when necessary
    my $needs_caller = $format =~ /%[FLPS]/;
    return sub {
        my %p = @_;
        $p{p} = delete $p{level};
        $p{m} = delete $p{message};
        $p{n} = "\n";
        $p{'%'} = '%';
        require POSIX;
        $p{i} = POSIX::getpid();

        if ($needs_caller) {
            my $depth = 0;
            $depth++ while caller($depth) =~ /^Log::Dispatch/;
            $depth += $Log::Dispatch::Config::CallerDepth;
            @p{qw(P F L)} = caller($depth);
            my $subname = (caller($depth+1))[3];
            $p{S} = $subname;
            $subname =~ s/^.*:://;
            $p{s} = $subname;
        }

        my $log = $format;
        $log =~ s{
            (%d(?:{(.*?)})?)|   # $1: datetime $2: datetime fmt
            (?:%([%pmFLPSnis])) # $3: others
        }{
            if ($1 && $2) {
                _strftime($2);
            }
            elsif ($1) {
                scalar localtime;
            }
            elsif ($3) {
                $p{$3};
            }
        }egx;
        return $log;
    };
}

{
    use vars qw($HasTimePiece);
    BEGIN { eval { require Time::Piece; $HasTimePiece = 1 }; }

    sub _strftime {
        my $fmt = shift;
        if ($HasTimePiece) {
            return Time::Piece->new->strftime($fmt);
        } else {
            require POSIX;
            return POSIX::strftime($fmt, localtime);
        }
    }
}

1;
__END__

=head1 NAME

Log::Dispatch::Config - Log4j for Perl

=head1 SYNOPSIS

  use Log::Dispatch::Config;
  Log::Dispatch::Config->configure('/path/to/log.conf');

  my $dispatcher = Log::Dispatch::Config->instance;
  $dispatcher->debug('this is debug message');
  $dispatcher->emergency('something *bad* happened!');

  # automatic reloading conf file, when modified
  Log::Dispatch::Config->configure_and_watch('/path/to/log.conf');

  # 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);

=head1 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.

=head1 METHOD

This module has a class method C<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 C<instance>
call).

So, what you should do is call C<configure> method once in somewhere
(like C<startup.pl> in mod_perl), then you can get configured
dispatcher instance via C<Log::Dispatch::Config-E<gt>instance>.

=head1 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
L<Log::Dispatch::Configurator::AppConfig> for details.

See L</"PLUGGABLE CONFIGURATOR"> for other config parsing scheme.

=head2 GLOBAL PARAMETERS

=over 4

=item dispatchers

  dispatchers = file screen

C<dispatchers> defines logger names, which will be splitted by spaces.
If this parameter is unset, no logging is done.

=item format

  format = [%d] [%p] %m at %F line %L%n

C<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)
  %%    % itself
  %i    process-id, returns POSIX::getpid()
        %S  subroutine with package name
        %s  subroutine without package name

Note that datetime (%d) format is configurable by passing C<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 C<strftime>
implementation, otherwise POSIX.

C<format> defined here would apply to all the log messages to
dispatchers. This parameter is B<optional>.

See L</"CALLER STACK"> for details about package, line number and
filename.

=back

=head2 PARAMETERS FOR EACH DISPATCHER

Parameters for each dispatcher should be prefixed with "name.", where
"name" is the name of each one, defined in global C<dispatchers>
parameter.

You can also use C<.ini> style grouping like:

  [foo]
  class = Log::Dispatch::File
  min_level = debug

See L<Log::Dispatch::Configurator::AppConfig> for details.

=over 4

=item class

  screen.class = Log::Dispatch::Screen

C<class> defines class name of Log::Dispatch subclasses. This
parameter is B<essential>.

=item format

  screen.format = -- %m --

C<format> defines log format which would be applied only to the
dispatcher. Note that if you define global C<format> also, C<%m> is
double formated (first global one, next each dispatcher one). This
parameter is B<optional>.

=item (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.

=back

=head1 SINGLETON

Declared C<instance> method would make C<Log::Dispatch::Config> class
singleton, so multiple calls of C<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, lifetime of
Singleton instance becomes sometimes messy. If you want to reload
singleton object manually, call C<reload> method.

  Log::Dispatch::Config->reload;

And, if you want to reload object on the fly, as you edit C<log.conf>
or something like that, what you should do is to call
C<configure_and_watch> method on Log::Dispatch::Config instead of
C<configure>. Then C<instance> call will check mtime of configuration
file, and compares it with instanciation time of singleton object. If
config file is newer than last instanciation, it will automatically
reload object.

=head1 NAMESPACE COLLISION

If you use Log::Dispatch::Config in multiple projects on the same perl
interpreter (like mod_perl), namespace collision would be a
problem. Bizzare thing will happen when you call
C<Log::Dispatch::Config-E<gt>configure> multiple times with differenct
argument.

In such cases, what you should do is to define your own logger class.

  package My::Logger;
  use Log::Dispatch::Config;
  use base qw(Log::Dispatch::Config);

Or make wrapper for it. See L<POE::Component::Logger> implementation
by Matt Sergeant.

=head1 PLUGGABLE CONFIGURATOR

If you pass filename to C<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 L</"CONFIGURATION">.

=over 4

=item *

Inherit from Log::Dispatch::Configurator.

  package Log::Dispatch::Configurator::Hardwired;
  use base qw(Log::Dispatch::Configurator);

Declare your own C<new> constructor. Stub C<new> method is defined in
Configurator base class, but you want to put parsing method in your
own constructor. In this example, we just bless reference. Note that
your object should be blessed hash.

  sub new { bless {}, shift }

=item *

Implement two required object methods C<get_attrs_global> and
C<get_attrs>.

C<get_attrs_global> should return hash reference of global parameters.
C<dispatchers> should be an array reference of names of dispatchers.

  sub get_attrs_global {
      my $self = shift;
      return {
          format => undef,
          dispatchers => [ qw(file screen) ],
      };
  }

C<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";
      }
  }

=item *

Implement optional C<needs_reload> and C<reload>
methods. C<needs_reload> should return boolean value if the object is
stale and needs reloading itself. This method will be triggered when
you configure logging object with C<configure_and_watch> method.

Stub config file mtime based C<needs_reload> method is declared in
Log::Dispatch::Configurator, so if your config class is based on
filesystem files, you do not need to reimplement this.

If you do not need I<singleton-ness> at all, always return true.

  sub needs_reload { 1 }

C<reload> method should redo parsing of the config file. Configurator
base class has a stub null C<reload> method, so you should better
override it.

See Log::Dispatch::Configurator::AppConfig source code for details.

=item *

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 C<configure> method call instead of config file name.

  use Log::Dispatch::Config;
  use Log::Dispatch::Configurator::Hardwired;

  my $config = Log::Dispatch::Configurator::Hardwired->new;
  Log::Dispatch::Config->configure($config);

=back

=head1 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 C<$Log::Dispatch::Config::CallerDepth>
to increase the caller stack depth. The default value is 0.

  sub logit {
      my($class, $level, $msg) = @_;
      local $Log::Dispatch::Config::CallerDepth = 1;
      $Logger->$level($msg);
  }

Note that your log caller's namespace should not match against
C</^Log::Dispatch/>, which makes this module confusing.

=head1 AUTHOR

Tatsuhiko Miyagawa E<lt>miyagawa@bulknews.netE<gt> with much help from
Matt Sergeant E<lt>matt@sergeant.orgE<gt>.

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

=head1 SEE ALSO

L<Log::Dispatch::Configurator::AppConfig>, L<Log::Dispatch>,
L<AppConfig>, L<POE::Component::Logger>

=cut
1	package Log::Dispatch::Config;
2
3	use strict;
4	use vars qw($VERSION);
5	$VERSION = 1.02;
6
7	use Log::Dispatch 2.00;
8	use base qw(Log::Dispatch);
9
10	# caller depth: can be changed from outside
11	$Log::Dispatch::Config::CallerDepth = 0;
12
13	sub _croak { require Carp; Carp::croak(@_); }
14
15	# accessor for symblic reference
16	sub __instance {
17	my $class = shift;
18	no strict 'refs';
19	my $instance = "$class\::_instance";
20	$$instance = shift if @_;
21	return $$instance;
22	}
23
24	sub _configurator_for {
25	my($class, $stuff) = @_;
26	return $stuff if UNIVERSAL::isa($stuff, 'Log::Dispatch::Configurator');
27	require Log::Dispatch::Configurator::AppConfig;
28	return Log::Dispatch::Configurator::AppConfig->new($stuff);
29	}
30
31	sub configure {
32	my($class, $stuff) = @_;
33	_croak "no config file or configurator supplied" unless $stuff;
34	my $config = $class->_configurator_for($stuff);
35	$config->myinit;
36	$class->__instance($config);
37	}
38
39	sub configure_and_watch {
40	my $class = shift;
41	$class->configure(@_);
42	$class->__instance->should_watch(1); # tells conf to watch config file
43	}
44
45	# backward compatibility
46	sub Log::Dispatch::instance { __PACKAGE__->instance; }
47
48	sub instance {
49	my $class = shift;
50
51	my $instance = $class->__instance or _croak "configure not yet called.";
52	if ($instance->isa('Log::Dispatch::Config')) {
53	# reload singleton on the fly
54	$class->reload if $instance->needs_reload;
55	}
56	else {
57	# first time call: $_instance is L::D::Configurator::*
58	$class->__instance($class->create_instance($instance));
59	}
60	return $class->__instance;
61	}
62
63	sub needs_reload {
64	my $self = shift;
65	return $self->{config}->should_watch && $self->{config}->needs_reload;
66	}
67
68	sub reload {
69	my $proto = shift;
70	my $class = ref $proto \|\| $proto;
71	my $instance = $class->__instance;
72	$instance->{config}->reload;
73	$class->__instance($class->create_instance($instance->{config}));
74	}
75
76	sub create_instance {
77	my($class, $config) = @_;
78	$config->{LDC_ctime} = time; # creation time
79
80	my $global = $config->get_attrs_global;
81	my $callback = $class->format_to_cb($global->{format}, 0);
82	my %dispatchers;
83	foreach my $disp (@{$global->{dispatchers}}) {
84	$dispatchers{$disp} = $class->config_dispatcher(
85	$disp, $config->get_attrs($disp),
86	);
87	}
88	my %args;
89	$args{callbacks} = $callback if defined $callback;
90	my $instance = $class->new(%args);
91
92	for my $dispname (keys %dispatchers) {
93	my $logclass = delete $dispatchers{$dispname}->{class};
94	$instance->add(
95	$logclass->new(
96	name => $dispname,
97	%{$dispatchers{$dispname}},
98	),
99	);
100	}
101
102	$instance->{config} = $config;
103	return $instance;
104	}
105
106	sub config_dispatcher {
107	my($class, $disp, $var) = @_;
108
109	my $dispclass = $var->{class} or _croak "class param missing for $disp";
110
111	eval qq{require $dispclass};
112	_croak $@ if $@ && $@ !~ /locate/;
113
114	if (exists $var->{format}) {
115	$var->{callbacks} = $class->format_to_cb(delete $var->{format}, 2);
116	}
117	return $var;
118	}
119
120	sub format_to_cb {
121	my($class, $format, $stack) = @_;
122	return undef unless defined $format;
123
124	# caller() called only when necessary
125	my $needs_caller = $format =~ /%[FLPS]/;
126	return sub {
127	my %p = @_;
128	$p{p} = delete $p{level};
129	$p{m} = delete $p{message};
130	$p{n} = "\n";
131	$p{'%'} = '%';
132	require POSIX;
133	$p{i} = POSIX::getpid();
134
135	if ($needs_caller) {
136	my $depth = 0;
137	$depth++ while caller($depth) =~ /^Log::Dispatch/;
138	$depth += $Log::Dispatch::Config::CallerDepth;
139	@p{qw(P F L)} = caller($depth);
140	my $subname = (caller($depth+1))[3];
141	$p{S} = $subname;
142	$subname =~ s/^.*:://;
143	$p{s} = $subname;
144	}
145
146	my $log = $format;
147	$log =~ s{
148	(%d(?:{(.*?)})?)\| # $1: datetime $2: datetime fmt
149	(?:%([%pmFLPSnis])) # $3: others
150	}{
151	if ($1 && $2) {
152	_strftime($2);
153	}
154	elsif ($1) {
155	scalar localtime;
156	}
157	elsif ($3) {
158	$p{$3};
159	}
160	}egx;
161	return $log;
162	};
163	}
164
165	{
166	use vars qw($HasTimePiece);
167	BEGIN { eval { require Time::Piece; $HasTimePiece = 1 }; }
168
169	sub _strftime {
170	my $fmt = shift;
171	if ($HasTimePiece) {
172	return Time::Piece->new->strftime($fmt);
173	} else {
174	require POSIX;
175	return POSIX::strftime($fmt, localtime);
176	}
177	}
178	}
179
180	1;
181	__END__
182
183	=head1 NAME
184
185	Log::Dispatch::Config - Log4j for Perl
186
187	=head1 SYNOPSIS
188
189	use Log::Dispatch::Config;
190	Log::Dispatch::Config->configure('/path/to/log.conf');
191
192	my $dispatcher = Log::Dispatch::Config->instance;
193	$dispatcher->debug('this is debug message');
194	$dispatcher->emergency('something bad happened!');
195
196	# automatic reloading conf file, when modified
197	Log::Dispatch::Config->configure_and_watch('/path/to/log.conf');
198
199	# or if you write your own config parser:
200	use Log::Dispatch::Configurator::XMLSimple;
201
202	my $config = Log::Dispatch::Configurator::XMLSimple->new('log.xml');
203	Log::Dispatch::Config->configure($config);
204
205	=head1 DESCRIPTION
206
207	Log::Dispatch::Config is a subclass of Log::Dispatch and provides a
208	way to configure Log::Dispatch object with configulation file
209	(default, in AppConfig format). I mean, this is log4j for Perl, not
210	with all API compatibility though.
211
212	=head1 METHOD
213
214	This module has a class method C<configure> which parses config file
215	for later creation of the Log::Dispatch::Config singleton instance.
216	(Actual construction of the object is done in the first C<instance>
217	call).
218
219	So, what you should do is call C<configure> method once in somewhere
220	(like C<startup.pl> in mod_perl), then you can get configured
221	dispatcher instance via C<Log::Dispatch::Config-E<gt>instance>.
222
223	=head1 CONFIGURATION
224
225	Here is an example of the config file:
226
227	dispatchers = file screen
228
229	file.class = Log::Dispatch::File
230	file.min_level = debug
231	file.filename = /path/to/log
232	file.mode = append
233	file.format = [%d] [%p] %m at %F line %L%n
234
235	screen.class = Log::Dispatch::Screen
236	screen.min_level = info
237	screen.stderr = 1
238	screen.format = %m
239
240	In this example, config file is written in AppConfig format. See
241	L<Log::Dispatch::Configurator::AppConfig> for details.
242
243	See L</"PLUGGABLE CONFIGURATOR"> for other config parsing scheme.
244
245	=head2 GLOBAL PARAMETERS
246
247	=over 4
248
249	=item dispatchers
250
251	dispatchers = file screen
252
253	C<dispatchers> defines logger names, which will be splitted by spaces.
254	If this parameter is unset, no logging is done.
255
256	=item format
257
258	format = [%d] [%p] %m at %F line %L%n
259
260	C<format> defines log format. Possible conversions format are
261
262	%d datetime string (ctime(3))
263	%p priority (debug, info, warning ...)
264	%m message string
265	%F filename
266	%L line number
267	%P package
268	%n newline (\n)
269	%% % itself
270	%i process-id, returns POSIX::getpid()
271	%S subroutine with package name
272	%s subroutine without package name
273
274	Note that datetime (%d) format is configurable by passing C<strftime>
275	fmt in braket after %d. (I know it looks quite messy, but its
276	compatible with Java Log4j ;)
277
278	format = [%d{%Y%m%d}] %m # datetime is now strftime "%Y%m%d"
279
280	If you have Time::Piece, this module uses its C<strftime>
281	implementation, otherwise POSIX.
282
283	C<format> defined here would apply to all the log messages to
284	dispatchers. This parameter is B<optional>.
285
286	See L</"CALLER STACK"> for details about package, line number and
287	filename.
288
289	=back
290
291	=head2 PARAMETERS FOR EACH DISPATCHER
292
293	Parameters for each dispatcher should be prefixed with "name.", where
294	"name" is the name of each one, defined in global C<dispatchers>
295	parameter.
296
297	You can also use C<.ini> style grouping like:
298
299	[foo]
300	class = Log::Dispatch::File
301	min_level = debug
302
303	See L<Log::Dispatch::Configurator::AppConfig> for details.
304
305	=over 4
306
307	=item class
308
309	screen.class = Log::Dispatch::Screen
310
311	C<class> defines class name of Log::Dispatch subclasses. This
312	parameter is B<essential>.
313
314	=item format
315
316	screen.format = -- %m --
317
318	C<format> defines log format which would be applied only to the
319	dispatcher. Note that if you define global C<format> also, C<%m> is
320	double formated (first global one, next each dispatcher one). This
321	parameter is B<optional>.
322
323	=item (others)
324
325	screen.min_level = info
326	screen.stderr = 1
327
328	Other parameters would be passed to the each dispatcher
329	construction. See Log::Dispatch::* manpage for the details.
330
331	=back
332
333	=head1 SINGLETON
334
335	Declared C<instance> method would make C<Log::Dispatch::Config> class
336	singleton, so multiple calls of C<instance> will all result in
337	returning same object.
338
339	my $one = Log::Dispatch::Config->instance;
340	my $two = Log::Dispatch::Config->instance; # same as $one
341
342	See GoF Design Pattern book for Singleton Pattern.
343
344	But in practice, in persistent environment like mod_perl, lifetime of
345	Singleton instance becomes sometimes messy. If you want to reload
346	singleton object manually, call C<reload> method.
347
348	Log::Dispatch::Config->reload;
349
350	And, if you want to reload object on the fly, as you edit C<log.conf>
351	or something like that, what you should do is to call
352	C<configure_and_watch> method on Log::Dispatch::Config instead of
353	C<configure>. Then C<instance> call will check mtime of configuration
354	file, and compares it with instanciation time of singleton object. If
355	config file is newer than last instanciation, it will automatically
356	reload object.
357
358	=head1 NAMESPACE COLLISION
359
360	If you use Log::Dispatch::Config in multiple projects on the same perl
361	interpreter (like mod_perl), namespace collision would be a
362	problem. Bizzare thing will happen when you call
363	C<Log::Dispatch::Config-E<gt>configure> multiple times with differenct
364	argument.
365
366	In such cases, what you should do is to define your own logger class.
367
368	package My::Logger;
369	use Log::Dispatch::Config;
370	use base qw(Log::Dispatch::Config);
371
372	Or make wrapper for it. See L<POE::Component::Logger> implementation
373	by Matt Sergeant.
374
375	=head1 PLUGGABLE CONFIGURATOR
376
377	If you pass filename to C<configure> method call, this module handles
378	the config file with AppConfig. You can change config parsing scheme
379	by passing another pluggable configurator object.
380
381	Here is a way to declare new configurator class. The example below is
382	hardwired version equivalent to the one above in L</"CONFIGURATION">.
383
384	=over 4
385
386	=item *
387
388	Inherit from Log::Dispatch::Configurator.
389
390	package Log::Dispatch::Configurator::Hardwired;
391	use base qw(Log::Dispatch::Configurator);
392
393	Declare your own C<new> constructor. Stub C<new> method is defined in
394	Configurator base class, but you want to put parsing method in your
395	own constructor. In this example, we just bless reference. Note that
396	your object should be blessed hash.
397
398	sub new { bless {}, shift }
399
400	=item *
401
402	Implement two required object methods C<get_attrs_global> and
403	C<get_attrs>.
404
405	C<get_attrs_global> should return hash reference of global parameters.
406	C<dispatchers> should be an array reference of names of dispatchers.
407
408	sub get_attrs_global {
409	my $self = shift;
410	return {
411	format => undef,
412	dispatchers => [ qw(file screen) ],
413	};
414	}
415
416	C<get_attrs> accepts name of a dispatcher and should return hash
417	reference of parameters associated with the dispatcher.
418
419	sub get_attrs {
420	my($self, $name) = @_;
421	if ($name eq 'file') {
422	return {
423	class => 'Log::Dispatch::File',
424	min_level => 'debug',
425	filename => '/path/to/log',
426	mode => 'append',
427	format => '[%d] [%p] %m at %F line %L%n',
428	};
429	}
430	elsif ($name eq 'screen') {
431	return {
432	class => 'Log::Dispatch::Screen',
433	min_level => 'info',
434	stderr => 1,
435	format => '%m',
436	};
437	}
438	else {
439	die "invalid dispatcher name: $name";
440	}
441	}
442
443	=item *
444
445	Implement optional C<needs_reload> and C<reload>
446	methods. C<needs_reload> should return boolean value if the object is
447	stale and needs reloading itself. This method will be triggered when
448	you configure logging object with C<configure_and_watch> method.
449
450	Stub config file mtime based C<needs_reload> method is declared in
451	Log::Dispatch::Configurator, so if your config class is based on
452	filesystem files, you do not need to reimplement this.
453
454	If you do not need I<singleton-ness> at all, always return true.
455
456	sub needs_reload { 1 }
457
458	C<reload> method should redo parsing of the config file. Configurator
459	base class has a stub null C<reload> method, so you should better
460	override it.
461
462	See Log::Dispatch::Configurator::AppConfig source code for details.
463
464	=item *
465
466	That's all. Now you can plug your own configurator (Hardwired) into
467	Log::Dispatch::Config. What you should do is to pass configurator
468	object to C<configure> method call instead of config file name.
469
470	use Log::Dispatch::Config;
471	use Log::Dispatch::Configurator::Hardwired;
472
473	my $config = Log::Dispatch::Configurator::Hardwired->new;
474	Log::Dispatch::Config->configure($config);
475
476	=back
477
478	=head1 CALLER STACK
479
480	When you call logging method from your subroutines / methods, caller
481	stack would increase and thus you can't see where the log really comes
482	from.
483
484	package Logger;
485	my $Logger = Log::Dispatch::Config->instance;
486
487	sub logit {
488	my($class, $level, $msg) = @_;
489	$Logger->$level($msg);
490	}
491
492	package main;
493	Logger->logit('debug', 'foobar');
494
495	You can adjust package variable C<$Log::Dispatch::Config::CallerDepth>
496	to increase the caller stack depth. The default value is 0.
497
498	sub logit {
499	my($class, $level, $msg) = @_;
500	local $Log::Dispatch::Config::CallerDepth = 1;
501	$Logger->$level($msg);
502	}
503
504	Note that your log caller's namespace should not match against
505	C</^Log::Dispatch/>, which makes this module confusing.
506
507	=head1 AUTHOR
508
509	Tatsuhiko Miyagawa E<lt>miyagawa@bulknews.netE<gt> with much help from
510	Matt Sergeant E<lt>matt@sergeant.orgE<gt>.
511
512	This library is free software; you can redistribute it and/or modify
513	it under the same terms as Perl itself.
514
515	=head1 SEE ALSO
516
517	L<Log::Dispatch::Configurator::AppConfig>, L<Log::Dispatch>,
518	L<AppConfig>, L<POE::Component::Logger>
519
520	=cut
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