Welcome to the Log::Log4perl recipe of the week. Today:
============================================================
Log::Log4perl Recipe of the Week (#14):
How can I drill down on references before logging them?
============================================================
If you've got a reference to a nested structure or object,
then you probably don't want to log it as "HASH(0x81141d4)"
but rather dump it as something like
$VAR1 = {
'a' => 'b',
'd' => 'e'
};
via a module like Data::Dumper. While it's syntactically
correct to say
$logger->debug(Data::Dumper::Dumper($ref));
this call imposes a huge performance penalty on your
application if the message is suppressed by Log::Log4perl,
because Data::Dumper will perform its expensive operations
in any case, because it doesn't know that its output will be
thrown away immediately.
As of Log::Log4perl 0.28, there's a better way: Use the
message output filter format as in
$logger->debug( {filter => \&Data::Dumper::Dumper,
value => $ref} );
and Log::Log4perl won't call the filter function unless the
message really gets written out to an appender. Just make
sure to pass the whole slew as a reference to a hash
specifying a filter function (as a sub reference) under the
key "filter" and the value to be passed to the filter
function in "value"). When it comes to logging,
Log::Log4perl will call the filter function, pass the
"value" as an argument and log the return value. Saves you
serious cycles.
Have fun! Until next week.
-- Mike
###################################
# Mike Schilli #
# log...@pe... #
# http://perlmeister.com #
# http://log4perl.sourceforge.net #
###################################
|
