Log::Dispatch - Dispatches messages to multiple Log::Dispatch::* objects
use Log::Dispatch;
my $dispatcher = Log::Dispatch->new;
$dispatcher->add( Log::Dispatch::File->new( name => 'file1',
min_level => 'debug',
filename => 'logfile' ) );
$dispatcher->log( level => 'info',
message => 'Blah, blah' );
my $sub = sub { my %p = @_; return reverse $p{message}; };
my $reversing_dispatcher = Log::Dispatch->new( callbacks => $sub );
This module manages a set of Log::Dispatch::* objects, allowing you to add and remove output objects as desired.
This parameter may be a single subroutine reference or an array reference of subroutine references. These callbacks will be called in the order they are given and passed a hash containing the following keys:
( message => $log_message, level => $log_level )
In addition, any key/value pairs passed to a logging method will be passed onto your callback.
The callbacks are expected to modify the message and then return a
single scalar containing that modified message. These callbacks will
be called when either the log or log_to methods are called and
will only be applied to a given message once. If they do not return
the message then you will get no output. Make sure to return the
message!
Adds a new a Log::Dispatch::* object to the dispatcher. If an object
of the same name already exists, then that object is replaced. A
warning will be issued if the $^W is true.
NOTE: This method can really take any object that has methods called 'name' and 'log'.
log_to method repeatedly).
Version 1.6 of Log::Dispatch adds a number of convenience methods for
logging. You may now call any valid log level (including valid
abbreviations) as a method on the Log::Dispatch object with a single
argument that is the message to be logged. This is converted into a
call to the log method with the appropriate level.
For example:
$dispatcher->alert('Strange data in incoming request');
translates to:
$dispatcher->log( level => 'alert', message => 'Strange data in incoming request' );
These methods act like Perl's print built-in when given a list of
arguments. Thus, the following calls are equivalent:
my @array = ('Something', 'bad', 'is', here');
$dispatcher->alert(@array);
my $scalar = "@array"; $dispatcher->alert($scalar);
One important caveat about these methods is that its not that forwards
compatible. If I were to add more parameters to the log call, it
is unlikely that these could be integrated into these methods without
breaking existing uses. This probably means that any future
parameters to the log method will never be integrated into these
convenience methods. OTOH, I don't see any immediate need to expand
the parameters given to the log method.
The log levels that Log::Dispatch uses are taken directly from the syslog man pages (except that I expanded them to full words). Valid levels are:
debug info notice warning error critical alert emergency
Alternately, the numbers 0 through 7 may be used (debug is 0 and emergency is 7). The syslog standard of 'err', 'crit', and 'emerg' is also acceptable.
This module is designed to be used as a one-stop logging system. In particular, it was designed to be easy to subclass so that if you want to handle messaging in a way not implemented in this package, you should be able to add this with minimal effort.
The basic idea behind Log::Dispatch is that you create a Log::Dispatch
object and then add various logging objects to it (such as a file
logger or screen logger). Then you call the log method of the
dispatch object, which passes the message to each of the objects,
which in turn decide whether or not to accept the message and what to
do with it.
This makes it possible to call single method and send a message to a log file, via email, to the screen, and anywhere else, all with very little code needed on your part, once the dispatching object has been created.
The logging levels that Log::Dispatch uses are borrowed from the standard UNIX syslog levels, except that where syslog uses partial words ("err") Log::Dispatch also allows the use of the full word as well ("error").
Making your own logging object is generally as simple as subclassing
Log::Dispatch::Output and overriding the new and log methods.
See the Log::Dispatch::Output docs for more details.
If you would like to create your own subclass for sending email then
it is even simpler. Simply subclass Log::Dispatch::Email and
override the send_email method. See the Log::Dispatch::Email
docs for more details.
A few people have written email to me asking me to add something that would tack a newline onto the end of all messages that don't have one. This will never happen. There are several reasons for this. First of all, Log::Dispatch was designed as a simple system to broadcast a message to multiple outputs. It does not attempt to understand the message in any way at all. Adding a newline implies an attempt to understand something about the message and I don't want to go there. Secondly, this is not very cross-platform and I don't want to go down the road of testing Config values to figure out what to tack onto messages based on OS.
I think people's desire to do this is because they are too focused on just the logging to files aspect of this module. In this case newlines make sense. However, imagine someone is using this module to log to a remote server and the interactions between the client and server use newlines as part of the control flow. Casually adding a newline could cause serious problems.
However, the 1.2 release adds the callbacks parameter for the Log::Dispatch object which you can easily use to add newlines to messages if you so desire.
Dominique Dumont has written Log::Dispatch::Tk, which allows log messages to show up in a Tk window.
Written by Tatsuhiko Miyagawa. Allows configuration of logging via a text file similar (or so I'm told) to how it is done with log4j.
Log::Dispatch::DBI, also written by Tatsuhiko Miyagawa. Log output to a database table.
A very different API for doing many of the same things that Log::Dispatch does. Originally written by Raphael Manfredi.
Dave Rolsky, <autarch@urth.org>
Log::Dispatch::ApacheLog, Log::Dispatch::Email, Log::Dispatch::Email::MailSend, Log::Dispatch::Email::MailSender, Log::Dispatch::Email::MailSendmail, Log::Dispatch::Email::MIMELite, Log::Dispatch::File, Log::Dispatch::Handle, Log::Dispatch::Output, Log::Dispatch::Screen, Log::Dispatch::Syslog