Log::Report::Dispatcher - manage message dispatching, display or logging


 Log::Report::Dispatcher is extended by


 use Log::Report;

 # The following will be created for you automatically
 dispatcher 'PERL', 'default', accept => 'NOTICE-';
 dispatcher close => 'default';  # after deamonize

 dispatcher 'FILE', 'log'
   , mode => 'DEBUG', to => '/var/log/mydir/myfile';

 # Full package name is used, same as 'FILE'
 dispatcher Log::Report::Dispatch::File => 'stderr'
   , to => \*STDERR, accept => 'NOTICE-';


In Log::Report, dispatchers are used to handle (exception) messages which are created somewhere else. Those message were produced (thrown) by Log::Report::error() and friends.

This base-class handles the creation of dispatchers, plus the common filtering rules. See the "DETAILS" section, below.




Terminate the dispatcher activities. The dispatcher gets disabled, to avoid the case that it is accidentally used. Returns undef (false) if the dispatcher was already closed.

Log::Report::Dispatcher->new($type, $name, %options)

Create a dispatcher. The $type of back-end to start is required, and listed in the "DESCRIPTION" part of this manual-page. For various external back-ends, special wrappers are created.

The $name must be uniquely identifying this dispatcher. When a second dispatcher is created (via Log::Report::dispatcher()) with the name of an existing dispatcher, the existing one will get replaced.

All %options which are not consumed by this base constructor are passed to the wrapped back-end. Some of them will check whether all %options are understood, other ignore unknown %options.

 -Option       --Default
  accept         depend on mode
  charset        <undef>
  format_reason  'LOWERCASE'
  locale         <system locale>
  mode           'NORMAL'
accept => REASONS

See Log::Report::Util::expand_reasons() for possible values. If the initial mode for this dispatcher does not need verbose or debug information, then those levels will not be accepted.

When the mode equals "NORMAL" (the default) then accept's default is NOTICE-. In case of "VERBOSE" it will be INFO-, ASSERT results in ASSERT-, and "DEBUG" in ALL.

charset => CHARSET

Convert the messages in the specified character-set (codeset). By default, no conversion will take place, because the right choice cannot be determined automatically.


How to show the reason text which is printed before the message. When a CODE is specified, it will be called with a translated text and the returned text is used.

locale => LOCALE

Overrules the global setting. Can be overruled by Log::Report::report(locale).

mode => 'NORMAL'|'VERBOSE'|'ASSERT'|'DEBUG'|0..3

Possible values are NORMAL (or 0 or undef), which will not show INFO or debug messages, VERBOSE (1; shows INFO not debug), ASSERT (2; only ignores TRACE messages), or DEBUG (3) which shows everything. See section "Run modes" in Log::Report.

You are advised to use the symbolic mode names when the mode is changed within your program: the numerical values are available for smooth Getopt::Long integration.



Returns the mode in use for the dispatcher as number. See new(mode) and "Run modes" in Log::Report.


Returns the unique name of this dispatcher.

$obj->needs( [$reason] )

Returns the list with all REASONS which are needed to fulfill this dispatcher's needs. When disabled, the list is empty, but not forgotten.

[0.999] when only one $reason is specified, it is returned if in the list.


The dispatcher $type, which is usually the same as the class of this object, but not in case of wrappers like for Log::Dispatch.



[1.13] Add one or more CODE blocks of caller lines which should not be collected for stack-traces or location display. A CODE gets called with an ARRAY of caller information, and returns true when that line should get skipped.

Warning: this logic is applied globally: on all dispatchers.


By default, all lines in the Log::Report packages are skipped from display, with a simple CODE as this:

  sub in_lr { $_[0][0] =~ m/^Log\:\:Report(?:\:\:|$)/ }

The only parameter to in_lr is the return of caller(). The first element of that ARRAY is the package name of a stack line.


Collect the information to be displayed as line where the error occurred.

$obj->collectStack( [$maxdepth] )
Log::Report::Dispatcher->collectStack( [$maxdepth] )

Returns an ARRAY of ARRAYs with text, filename, line-number.

$obj->log(HASH-$of-%options, $reason, $message, $domain)

This method is called by Log::Report::report() and should not be called directly. Internally, it will call translate(), which does most $of the work.


[1.13] Returns the number of nestings in the stack which should be skipped to get outside the Log::Report (and related) modules. The end-user does not want to see those internals in stack-traces.

 -Option    --Default
  abstract    1
  call        <required>
  filename    <required>
  linenr      <required>
  max_line    undef
  max_params  8
  package     <required>
  params      <required>
abstract => INTEGER

The higher the abstraction value, the less details are given about the caller. The minimum abstraction is specified, and then increased internally to make the line fit within the max_line margin.

call => STRING
filename => STRING
linenr => INTEGER
max_line => INTEGER
max_params => INTEGER
package => CLASS
params => ARRAY
$obj->translate(HASH-$of-%options, $reason, $message)

See "Processing the message", which describes the actions taken by this method. A string is returned, which ends on a new-line, and may be multi-line (in case a stack trace is produced).


Available back-ends

When a dispatcher is created (via new() or Log::Report::dispatcher()), you must specify the TYPE of the dispatcher. This can either be a class name, which extends a Log::Report::Dispatcher, or a pre-defined abbreviation of a class name. Implemented are:

Log::Report::Dispatcher::Perl (abbreviation 'PERL')

Use Perl's own print(), warn() and die() to ventilate reports. This is the default dispatcher.

Log::Report::Dispatcher::File (abbreviation 'FILE')

Logs the message into a file, which can either be opened by the class or be opened before the dispatcher is created.

Log::Report::Dispatcher::Syslog (abbreviation 'SYSLOG')

Send messages into the system's syslog infrastructure, using Sys::Syslog.

Log::Report::Dispatcher::Callback (abbreviation 'CALLBACK')

Calls any CODE reference on receipt of each selected message, for instance to send important message as email or SMS.


All of the Log::Dispatch::Output extensions can be used directly. The Log::Report::Dispatcher::LogDispatch will wrap around that back-end.


Use the Log::Log4perl main object to write to dispatchers. This infrastructure uses a configuration file.

Log::Report::Dispatcher::Try (abbreviation 'TRY')

Used by function Log::Report::try(). It collects the exceptions and can produce them on request.

Processing the message

Addition information

The modules which use Log::Report will only specify the base of the message string. The base dispatcher and the back-ends will extend this message with additional information:

. the reason
. the filename/line-number where the problem appeared
. the filename/line-number where it problem was reported
. the error text in $!
. a stack-trace
. a trailing new-line

When the message is a translatable object (Log::Report::Message, for instance created with Log::Report::__()), then the added components will get translated as well. Otherwise, all will be in English.

Exactly what will be added depends on the actual mode of the dispatcher (change it with mode(), initiate it with new(mode)).

                        mode mode mode mode
 trace    program  ...                 S
 assert   program  ...            SL   SL
 info     program  T..       S    S    S
 notice   program  T..  S    S    S    S
 mistake  user     T..  S    S    S    SL
 warning  program  T..  S    S    SL   SL
 error    user     TE.  S    S    SL   SC
 fault    system   TE!  S    S    SL   SC
 alert    system   T.!  SL   SL   SC   SC
 failure  system   TE!  SL   SL   SC   SC
 panic    program  .E.  SC   SC   SC   SC

 T - usually translated
 E - exception (execution interrupted)
 ! - will include $! text at display
 L - include filename and linenumber
 S - show/print when accepted
 C - stack trace (like Carp::confess())


With a filter, you can block or modify specific messages before translation. There may be a wish to change the REASON of a report or its content. It is not possible to avoid the exit which is related to the original message, because a module's flow depends on it to happen.

When there are filters defined, they will be called in order of definition. For each of the dispatchers which are called for a certain REASON (which accept that REASON), it is checked whether its name is listed for the filter (when no names where specified, then the filter is applied to all dispatchers).

When selected, the filter's CODE reference is called with four arguments: the dispatcher object (a Log::Report::Dispatcher), the HASH-of-OPTIONS passed as optional first argument to Log::Report::report(), the REASON, and the MESSAGE. Returned is the new REASON and MESSAGE. When the returned REASON is undef, then the message will be ignored for that dispatcher.

Be warned about processing the MESSAGE: it is a Log::Report::Message object which may have a prepend string and append string or object. When the call to Log::Report::report() contained multiple comma-separated components, these will already have been joined together using concatenation (see Log::Report::Message::concat().

. Example: a filter on syslog

 dispatcher filter => \&myfilter, 'syslog';

 # ignore all translatable and non-translatable messages containing
 # the word "skip"
 sub myfilter($$$$)
 {   my ($disp, $opts, $reason, $message) = @_;
     return () if $message->untranslated =~ m/\bskip\b/;
     ($reason, $message);

. Example: take all mistakes and warnings serious

 dispatch filter => \&take_warns_seriously;
 sub take_warns_seriously($$$$)
 {   my ($disp, $opts, $reason, $message) = @_;
       $reason eq 'MISTAKE' ? (ERROR   => $message)
     : $reason eq 'WARNING' ? (FAULT   => $message)
     :                        ($reason => $message);


This module is part of Log-Report distribution version 1.36, built on October 27, 2023. Website:


Copyrights 2007-2023 by [Mark Overmeer <>]. For other contributors see ChangeLog.

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