NAME

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

SYNOPSIS

    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
    );

    Log::Log4perl->init(\$conf);

    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.");

DESCRIPTION

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

appender

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.

max_messages

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.

trigger_level

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. Defining

    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

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() method:

        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.

Shortcut

DEVELOPMENT NOTES

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 future.

LEGALESE

AUTHOR

2004, Mike Schilli <m@perlmeister.com>