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 <miyagawa@bulknews.net> with much help from Matt
Sergeant <matt@sergeant.org>.
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