Log::Any::Adapter::Development(3p)

NAME
Log::Any::Adapter::Development - Manual for developing new Log::Any adapters

VERSION
version 1.719

SYNOPSIS
The adapter module:

   package Log::Any::Adapter::YAL;
   use strict;
   use warnings;
   use Log::Any::Adapter::Util ();
   use base qw(Log::Any::Adapter::Base);

   # Optionally initialize object, e.g. for delegation
   #
   sub init {
       my ($self) = @_;

       $self->{attr} = ...;
   }

   # Create logging methods: debug, info, etc.
   #
   foreach my $method ( Log::Any::Adapter::Util::logging_methods() ) {
       no strict 'refs';
       *$method = sub { ... };
   }

   # or, support structured logging instead
   sub structured {
       my ($self, $level, $category, @args) = @_;
       # ... process and log all @args
   }

   # Create detection methods: is_debug, is_info, etc.
   #
   foreach my $method ( Log::Any::Adapter::Util::detection_methods() ) {
       no strict 'refs';
       *$method = sub { ... };
   }

and the application:

   Log::Any->set_adapter('YAL');

DESCRIPTION
This document describes how to implement a new Log::Any adapter.

The easiest way to start is to look at the source of existing adapters, such as Log::Any::Adapter::Log4perl and Log::Any::Adapter::Dispatch.

NAMING
If you are going to publicly release your adapter, call it 'Log::Any::Adapter::something' so that users can use it with

    Log::Any->set_adapter(I<something>);

If it's an internal driver, you can call it whatever you like and use it like

    Log::Any->set_adapter('+My::Log::Adapter');

BASE CLASS
All adapters must directly or indirectly inherit from Log::Any::Adapter::Base.

LOG LEVELS
Log::Any supports the following log levels:

•   trace

•   debug

•   info

•   notice

•   warning

•   error

•   critical

•   alert

•   emergency

If the logging mechanism used by your adapter supports different levels, it's your responsibility to map them appropriately when you implement the logging and detection methods described below. For example, if your mechanism only supports "debug", "normal" and "fatal" levels, you might map the levels like this:

•   debug: trace, debug

•   normal: info, notice, warning

•   fatal: error, critical, alert, emergency

METHODS

  Constructor
The constructor ("new") is provided by Log::Any::Adapter::Base. It will:

•   place any adapter arguments into a hash, along with the category

•   bless the hash into your subclass

•   call "init" which may be optionally provided by your subclass

At this point, overriding the default constructor is not supported. Hopefully it will not be needed.

The constructor is called whenever a log object is requested. e.g. If the application initializes Log::Any like so:

    Log::Any->set_adapter('Log::YAL', yal_object => $yal, depth => 3);

and then a class requests a logger like so:

    package Foo;
    use Log::Any qw($log);

Then $log will be populated with the return value of:

    Log::Any::Adapter::Yal->new(yal_object => $yal, depth => 3, category => 'Foo');

This is memoized, so if the same category should be requested again (e.g. through a separate "get_logger" call, the same object will be returned. Therefore, you should try to avoid anything non-deterministic in your "init" function.

  Logging methods
The following methods have no default implementation, and MUST be defined by your subclass, unless your adapter supports "Structured logging":

•   trace ($msg)

•   debug ($msg)

•   info ($msg)

•   notice ($msg)

•   warning ($msg)

•   error ($msg)

•   critical ($msg)

•   alert ($msg)

•   emergency ($msg)

These methods must log a message at the specified level.

To help generate these methods programmatically, you can get a list of the sub names with the Log::Any::Adapter::Util::logging_methods function.

  Log-level detection methods (required)
The following methods have no default implementation, and MUST be defined by your subclass:

•   is_trace ()

•   is_debug ()

•   is_info ()

•   is_notice ()

•   is_warning ()

•   is_error ()

•   is_critical ()

•   is_alert ()

•   is_emergency ()

These methods must return a boolean indicating whether the specified level is active, i.e. whether the adapter is listening for messages of that level.

To help generate these methods programmatically, you can get a list of the sub names with the Log::Any::Adapter::Util::detection_methods function.

  Structured logging
Your adapter can choose to receive structured data instead of a string. In this case, instead of implementing all the "Logging methods", you define a single method called "structured". The method receives the log level, the category, and all arguments that were passed to the logging function, so be prepared to not only handle strings, but also hashrefs, arrayrefs, coderefs, etc.

  Aliases
Aliases (e.g. "err" for "error") are handled by Log::Any::Proxy and will call the corresponding real name in your adapter class. You do not need to implement them in your adapter.

  Optional methods
The following methods have no default implementation but MAY be provided by your subclass:

init
    This is called after the adapter object is created and blessed into your class. Perform any necessary validation or initialization here. For example, you would use "init" to create a logging object for delegation, or open a file or socket, etc.

  Support methods
The following Log::Any::Adapter::Base method may be useful for defining adapters via delegation:

delegate_method_to_slot ($slot, $method, $adapter_method)
    Handle the specified $method by calling $adapter_method on the object contained in "$self->{$slot}".

    See Log::Any::Adapter::Dispatch and Log::Any::Adapter::Log4perl for examples of usage.

The following Log::Any::Adapter::Util functions give you a list of methods that you need to implement. You can get logging methods, detection methods or both:

•   Log::Any::Adapter::Util::logging_methods

•   Log::Any::Adapter::Util::detection_methods

•   Log::Any::Adapter::Util::logging_and_detection_methods

AUTHORS

•   Jonathan Swartz <swartz@pobox.com>

•   David Golden <dagolden@cpan.org>

•   Doug Bell <preaction@cpan.org>

•   Daniel Pittman <daniel@rimspace.net>

•   Stephen Thirlwall <sdt@cpan.org>

COPYRIGHT AND LICENSE
This software is copyright (c) 2017 by Jonathan Swartz, David Golden, and Doug Bell.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.