NAME

Log::Message;

SYNOPSIS use Log::Message private => 0, config => '/our/cf_file';

    my $log = Log::Message->new(    private => 1,
                                    level   => 'log',
                                    config  => '/my/cf_file',
                               );

    $log->store('this is my first message');

    $log->store(    message => 'message #2',
                    tag     => 'MY_TAG',
                    level   => 'carp',
                    extra   => ['this is an argument to the handler'],
               );

    my @last_five_items = $log->retrieve(5);

    my @items = $log->retrieve( tag     => qr/my_tag/i,
                                message => qr/\d/,
                                remove  => 1,
                              );

    my @items = $log->final( level => qr/carp/, amount => 2 );

    my $first_error = $log->first()

    # croak with the last error on the stack
    $log->final->croak;

    # empty the stack
    $log->flush();


=head1 DESCRIPTION

Log::Message is a generic message storage mechanism. It allows you to store messages on a stack -- either shared or private -- and assign meta-data to it. Some meta-data will automatically be added for you, like a timestamp and a stack trace, but some can be filled in by the user, like a tag by which to identify it or group it, and a level at which to handle the message (for example, log it, or die with it)

Log::Message also provides a powerfull way of searching through items by regexes on messages, tags and level.

Hierarchy

There are 4 modules of interest when dealing with the Log::Message::* modules:

Log::Message: Log::Message provides a few methods to manipulate the stack it keeps. It has the option of keeping either a private or a public stack. More on this below.
Log::Message::Item: These are individual message items, which are objects that contain the user message as well as the meta-data described above. See the the Log::Message::Item manpage manpage to see how to extract this meta-data and how to work with the Item objects. You should never need to create your own Item objects, but knowing about their methods and accessors is important if you want to write your own handlers. (See below)
Log::Message::Handlers: These are a collection of handlers that will be called for a level that is used on a the Log::Message::Item manpage object. For example, if a message is logged with the 'carp' level, the 'carp' handler from the Log::Message::Handlers manpage will be called. See the the Log::Message::Handlers manpage manpage for more explenation about how handlers work, which one are available and how to create your own.
Log::Message::Config: Per Log::Message object, there is a configuration required that will fill in defaults if the user did not specify arguments to override them (like for example what tag will be set if none was provided), the Log::Message::Config manpage handles the creation of these configurations.; Configuration can be specified in 4 ways:

Options

When using Log::Message, or creating a new Log::Message object, you can supply various options to alter it's behaviour. Of course, there are sensible defaults should you choose to omit these options.

Below an explenation of all the options and how they work.

config: The path to a configuration file to be read. See the manpage of the Log::Message::Config manpage for the required format; These options will be overridden by any explicit arguments passed.
private: Wether to create, by default, private or shared objects. If you choose to create shared objects, all Log::Message objects will use the same stack.; This means that even though every module may make it's own $log object they will still be sharing the same error stack on which they are putting errors and from which they are retrieving.; This can be usefull in big projects.; If you choose to create a private object, then the stack will of course be private to this object, but it will still fall back to the shared config should no private config or overriding arguments be provided.
verbose: Log::Message makes use of another module to validate it's arguments, which is called the Params::Check manpage, which is a lightweight, yet powerful input checker and parser. (See the the Params::Check manpage manpage for details).; The verbose setting will control whether this module will generate warnings if something improper is passed as input, or merely silently returns undef, at which point Log::Message will generate a warning.; It's best to just leave this at it's default value, which is '1'
tag: The tag to add to messages if none was provided. If neither your config, nor any specific arguments supply a tag, then Log::Message will set it to 'NONE'; Tags are usefull for searching on or grouping by. For example, you could tag all the messages you want to go to the user as 'USER ERROR' and all those that are only debug information with 'DEBUG'.; At the end of your program, you could then print all the ones tagged 'USER ERROR' to STDOUT, and those marked 'DEBUG' to a log file.
level: level describes what action to take when a message is logged. Just like tag, Log::Message will provide a default (which is 'log') if neither your config file, nor any explicit arguments are given to override it.; See the Log::Message::Handlers manpage to see what handlers are available by default and what they do, as well as to how to add your own handlers.
remove: This indicates whether or not to automatically remove the messages from the stack when you've retrieved them. The default setting provided by Log::Message is '0': do not remove.
chrono: This indicates whether messages should always be fetched in chronological order or not. This simply means that you can choose whether, when retrieving items, the item most recently added should be returned first, or the one that had been added most long ago.; The default is to return the newest ones first

Methods

new

This creates a new Log::Message object; The parameters it takes are described in the Options section below and let it just be repeated that you can use these options like this:

    my $log = Log::Message->new( %options );

as well as during use time, like this:

    use Log::Message option1 => value, option2 => value

There are but 3 rules to keep in mind:

use

store

This will create a new Item object and store it on the stack.

Possible arguments you can give to it are:

message: This is the only argument that is required. If no other arguments are given, you may even leave off the message key. The argument will then automatically be assumed to be the message.
tag: The tag to add to this message. If not provided, Log::Message will look in your configuration for one.
level: The level at which this message should be handled. If not provided, Log::Message will look in your configuration for one.
extra: This is an array ref with arguments passed to the handler for this message, when it is called from store();; The handler will receive them as a normal list

store() will return true upon success and undef upon failure, as well as issue a warning as to why it failed.

retrieve

This will retrieve all message items matching the criteria specified from the stack.

Here are the criteria you can discriminate on:

tag: A regex to which the tag must adhere. For example qr/\w/.
level: A regex to which the level must adhere.
message: A regex to which the message must adhere.
amount: Maximum amount of errors to return
chrono: Return in chronological order, or not?
remove: Remove items from the stack upon retrieval?

In scalar context it will return the first item matching your criteria and in list context, it will return all of them.

If an error occurs while retrieving, a warning will be issued and undef will be returned.

first

This is a shortcut for retrieving the first item(s) stored on the stack. It will default to only retrieving one if called with no arguments, and will always return results in chronological order.

If you only supply one argument, it is assumed to be the amount you wish returned.

Furthermore, it can take the same arguments as retrieve can.

first

This is a shortcut for retrieving the last item(s) stored on the stack. It will default to only retrieving one if called with no arguments, and will always return results in reverse chronological order.

If you only supply one argument, it is assumed to be the amount you wish returned.

Furthermore, it can take the same arguments as retrieve can.

flush

This removes all items from the stack and returns them to the caller

AUTHOR

This module by Jos Boumans <kane@cpan.org>.

Acknowledgements

Thanks to Ann Barcomb for her suggestions.

COPYRIGHT

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

/usr/local/perl/lib/site_perl/5.8.5/Log/Message.pm