Provided by: liblog-log4perl-perl_1.49-1_all bug


           Log::Log4perl::Appender::Buffer - Buffering Appender


           use Log::Log4perl qw(:easy);

           my $conf = qq(
           log4perl.category                  = DEBUG, Buffer

               # Regular Screen Appender
           log4perl.appender.Screen           = Log::Log4perl::Appender::Screen
           log4perl.appender.Screen.stdout    = 1
           log4perl.appender.Screen.layout    = PatternLayout
           log4perl.appender.Screen.layout.ConversionPattern = %d %p %c %m %n

               # Buffering appender, using the appender above as outlet
           log4perl.appender.Buffer               = Log::Log4perl::Appender::Buffer
           log4perl.appender.Buffer.appender      = Screen
           log4perl.appender.Buffer.trigger_level = ERROR


           DEBUG("This message gets buffered.");
           INFO("This message gets buffered also.");

           # Time passes. Nothing happens. But then ...

           print "It's GO time!!!\n";

           ERROR("This message triggers a buffer flush.");


       "Log::Log4perl::Appender::Buffer" takes these arguments:

           Specifies the name of the appender it buffers messages for. The appender specified
           must be defined somewhere in the configuration file, not necessarily before the
           definition of "Log::Log4perl::Appender::Buffer".

           Specifies the maximum number of messages the appender will hold in its ring buffer.
           "max_messages" is optional. By default, "Log::Log4perl::Appender::Buffer" will not
           limit the number of messages buffered. This might be undesirable in long-running
           processes accumulating lots of messages before a flush happens. If "max_messages" is
           set to a numeric value, "Log::Log4perl::Appender::Buffer" will displace old messages
           in its buffer to make room if the buffer is full.

           If trigger_level is set to one of Log4perl's levels (see Log::Log4perl::Level), a
           "trigger" function will be defined internally to flush the buffer if a message with a
           priority of $level or higher comes along. This is just a convenience function.

               log4perl.appender.Buffer.trigger_level = ERROR

           is equivalent to creating a trigger function like

               log4perl.appender.Buffer.trigger = sub {   \
                   my($self, $params) = @_;               \
                   return $params->{log4p_level} >=       \
                          $Log::Log4perl::Level::ERROR; }

           See the next section for defining generic trigger functions.

           "trigger" holds a reference to a subroutine, which "Log::Log4perl::Appender::Buffer"
           will call on every incoming message with the same parameters as the appender's "log()"

                   my($self, $params) = @_;

           $params references a hash containing the message priority (key "l4p_level"), the
           message category (key "l4p_category") and the content of the message (key "message").

           If the subroutine returns 1, it will trigger a flush of buffered messages.



       "Log::Log4perl::Appender::Buffer" is a composite appender.  Unlike other appenders, it
       doesn't log any messages, it just passes them on to its attached sub-appender.  For this
       reason, it doesn't need a layout (contrary to regular appenders).  If it defines none,
       messages are passed on unaltered.

       Custom filters are also applied to the composite appender only.  They are not applied to
       the sub-appender. Same applies to appender thresholds. This behaviour might change in the


       Copyright 2002-2013 by Mike Schilli <> and Kevin Goess <>.

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


       Please contribute patches to the project on Github:


       Send bug reports or requests for enhancements to the authors via our

       MAILING LIST (questions, bug reports, suggestions/patches):

       Authors (please contact them via the list above, not directly): Mike Schilli
       <>, Kevin Goess <>

       Contributors (in alphabetical order): Ateeq Altaf, Cory Bennett, Jens Berthold, Jeremy
       Bopp, Hutton Davidson, Chris R. Donnelly, Matisse Enzer, Hugh Esco, Anthony Foiani, James
       FitzGibbon, Carl Franks, Dennis Gregorovic, Andy Grundman, Paul Harrington, Alexander
       Hartmaier  David Hull, Robert Jacobson, Jason Kohles, Jeff Macdonald, Markus Peter, Brett
       Rann, Peter Rabbitson, Erik Selberg, Aaron Straup Cope, Lars Thegler, David Viner, Mac