Appender::Limit

Section: User Contributed Perl Documentation (3)
Updated: 2021-02-08
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NAME

Log::Log4perl::Appender::Limit - Limit message delivery via block period

SYNOPSIS

    use Log::Log4perl qw(:easy);

    my $conf = qq(
      log4perl.category = WARN, Limiter
    
          # Email appender
      log4perl.appender.Mailer          = Log::Dispatch::Email::MailSend
      log4perl.appender.Mailer.to       = drone\@pageme.com
      log4perl.appender.Mailer.subject  = Something's broken!
      log4perl.appender.Mailer.buffered = 0
      log4perl.appender.Mailer.layout   = PatternLayout
      log4perl.appender.Mailer.layout.ConversionPattern=%d %m %n

          # Limiting appender, using the email appender above
      log4perl.appender.Limiter              = Log::Log4perl::Appender::Limit
      log4perl.appender.Limiter.appender     = Mailer
      log4perl.appender.Limiter.block_period = 3600
    );

    Log::Log4perl->init(\$conf);
    WARN("This message will be sent immediately.");
    WARN("This message will be delayed by one hour.");
    sleep(3601);
    WARN("This message plus the last one will be sent now, seperately.");

DESCRIPTION

"appender"

Specifies the name of the appender used by the limiter. The appender specified must be defined somewhere in the configuration file, not necessarily before the definition of "Log::Log4perl::Appender::Limit".

"block_period"

Period in seconds between delivery of messages. If messages arrive in between, they will be either saved (if "accumulate" is set to a true value) or discarded (if "accumulate" isn't set).

"persistent"

File name in which "Log::Log4perl::Appender::Limit" persistently stores delivery times. If omitted, the appender will have no recollection of what happened when the program restarts.

"max_until_flushed"

Maximum number of accumulated messages. If exceeded, the appender flushes all messages, regardless if the interval set in "block_period" has passed or not. Don't mix with "max_until_discarded".

"max_until_discarded"

Maximum number of accumulated messages. If exceeded, the appender will simply discard additional messages, waiting for "block_period" to expire to flush all accumulated messages. Don't mix with "max_until_flushed".

"appender_method_on_flush"

Optional method name to be called on the appender attached to the limiter when messages are flushed. For example, to have the sample code in the SYNOPSIS section bundle buffered emails into one, change the mailer's "buffered" parameter to 1 and set the limiters "appender_method_on_flush" value to the string "flush":

      log4perl.category = WARN, Limiter
    
          # Email appender
      log4perl.appender.Mailer          = Log::Dispatch::Email::MailSend
      log4perl.appender.Mailer.to       = drone\@pageme.com
      log4perl.appender.Mailer.subject  = Something's broken!
      log4perl.appender.Mailer.buffered = 1
      log4perl.appender.Mailer.layout   = PatternLayout
      log4perl.appender.Mailer.layout.ConversionPattern=%d %m %n

          # Limiting appender, using the email appender above
      log4perl.appender.Limiter              = Log::Log4perl::Appender::Limit
      log4perl.appender.Limiter.appender     = Mailer
      log4perl.appender.Limiter.block_period = 3600
      log4perl.appender.Limiter.appender_method_on_flush = flush

This will cause the mailer to buffer messages and wait for "flush()" to send out the whole batch. The limiter will then call the appender's "flush()" method when it's own buffer gets flushed out.

If the appender attached to "Limit" uses "PatternLayout" with a timestamp specifier, you will notice that the message timestamps are reflecting the original log event, not the time of the message rendering in the attached appender. Major trickery has been applied to accomplish this (Cough!).

DEVELOPMENT NOTES

"Log::Log4perl::Appender::Limit" 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 future.

LICENSE

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

AUTHOR

Please contribute patches to the project on Github:

    http://github.com/mschilli/log4perl

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

MAILING LIST (questions, bug reports, suggestions/patches): log4perl-devel@lists.sourceforge.net

Authors (please contact them via the list above, not directly): Mike Schilli <m@perlmeister.com>, Kevin Goess <cpan@goess.org>

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 Yang.