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Manual Reference Pages  -  LOG::CONTEXTUAL::ROLE::ROUTER (3)

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Log::Contextual::Role::Router - Abstract interface between loggers and logging code blocks



version 0.006005


  package MyApp::Log::Router;

  use Moo;
  use Log::Contextual::SimpleLogger;

  with Log::Contextual::Role::Router;

  has logger => (is => lazy);

  sub _build_logger {
     return Log::Contextual::SimpleLogger->new({ levels_upto => debug });

  sub before_import {
     my ($self, %export_info) = @_;
     my $exporter = $export_info{exporter};
     my $target = $export_info{target};
     print STDERR "Package $target will import from $exporter\n";

  sub after_import {
     my ($self, %export_info) = @_;
     my $exporter = $export_info{exporter};
     my $target = $export_info{target};
     print STDERR "Package $target has imported from $exporter\n";

  sub handle_log_request {
     my ($self, %message_info) = @_;
     my $log_code_block = $message_info{message_sub};
     my $args = $message_info{message_args};
     my $log_level_name = $message_info{message_level};
     my $logger = $self->logger;
     my $is_active = $logger->can("is_${log_level_name}");

     return unless defined $is_active && $logger->$is_active;
     my $log_message = $log_code_block->(@$args);

  package MyApp::Log::Contextual;

  use Moo;
  use MyApp::Log::Router;

  extends Log::Contextual;

  #This example router is a singleton
  sub router {
     our $Router ||= MyApp::Log::Router->new

  package main;

  use strict;
  use warnings;
  use MyApp::Log::Contextual qw(:log);

  log_info { "Hello there" };


Log::Contextual has three parts
Export manager and logging method generator These tasks are handled by the Log::Contextual package.
Logger selection and invocation The logging functions generated and exported by Log::Contextual call a method on an instance of a log router object which is responsible for invoking any loggers that should get an opportunity to receive the log message. The Log::Contextual::Router class implements the set_logger() and with_logger() functions as well as uses the arg_ prefixed functions to configure itself and provide the standard Log::Contextual logger selection API.
Log message formatting and output The logger objects themselves accept or reject a log message at a certain log level with a guard method per level. If the logger is going to accept the log message the router is then responsible for executing the log message code block and passing the generated message to the logging object’s log method.


before_import($self, %import_info)
after_import($self, %import_info) These two required methods are called with identical arguments at two different places during the import process. The before_import() method is invoked prior to the logging subroutines being exported into the target package and after_import() is called when the export is completed but before control returns to the package that imported the API.

The arguments are passed as a hash with the following keys:
exporter This is the name of the package that has been imported. It can also be ’Log::Contextual’ itself. In the case of the synopsis the value for exporter would be ’MyApp::Log::Contextual’.
target This is the package name that is importing the logging API. In the case of the synopsis the value would be ’main’.
arguments This is a hash reference containing the configuration values that were provided for the import. The key is the name of the configuration item that was specified without the leading hyphen (’-’). For instance if the logging API is imported as follows

  use Log::Contextual qw( :log ), -logger => Custom::Logger->new({ levels => [qw( debug )] });

then $import_info{arguments}->{logger} would contain that instance of Custom::Logger.

handle_log_request($self, %message_info) This method is called by Log::Contextual when a log event happens. The arguments are passed as a hash with the following keys
exporter This is the name of the package that created the logging methods used to generate the log event.
caller_package This is the name of the package that the log event has happened inside of.
caller_level This is an integer that contains the value to pass to caller() that will provide information about the location the log event was created at.
log_level This is the name of the log level associated with the log event.
message_sub This is the message generating code block associated with the log event passed as a subref. If the logger accepts the log request the router should execute the subref to create the log message and then pass the message as a string to the logger.
message_args This is an array reference that contains the arguments given to the message generating code block. When invoking the message generator it will almost certainly be expecting these argument values as well.


Arthur Axel fREW Schmidt <>


This software is copyright (c) 2015 by Arthur Axel fREW Schmidt.

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

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perl v5.20.3 LOG::CONTEXTUAL::ROLE::ROUTER (3) 2015-03-14

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