Using Data::Dumper With Log4perl

I’m currently working on some Perl code for a change, and as part of a refactor I’ve added log4perl in to support my debugging.

I tend to overuse Data::Dumper as it’s so useful for seeing what is going on inside an object, and I had been passing the results directly to log4perl. This is actually very inefficient if I changed my logging level to turn off the dumps, as Dumper would still run, but the results would just be ignored.

Thankfully log4perl supports filters, so I can use this to defer the Dumper operation until it actually needs to be output.

get_logger(ref $self)->trace({
  filter => &Data::Dumper::Dumper,
  value  => $data

In the above example, I’m getting the singleton instance of log4perl for my current class, then calling trace, and saying I’d like the $data passed through Data::Dumper::Dumper. This will only be filtered if I have trace level monitoring enabled, if not it will be silently ignored and not executed, saving me valuable resources.