How can I tell if Log4perl emitted any warnings during a run?

Question

I've been using Log4perl extensively in a number of scripts. I'd like to augment those scripts to set an error code if any WARN or ERROR messages have been logged. I couldn't find any obvious way to do this based on existing documentation.

I'd like to avoid a brute-force rewrite of my existing scripts to add a check on every WARN or ERROR log message; I'd prefer to handle it prior to script exit if possible like this pseudocode:

if $log->has_warnings_or_errors then
  exit 1
else
  exit 0

Is there any easy way to call Log4Perl to determine if the current logger has issues messages of certain levels?

Answer 1

Use an appender.

MyCounter.pm:

package MyCounter;

use warnings;
use strict;

use Log::Log4perl::Level;

sub new {
  my($class,%arg) = @_;
  bless {} => $class;
}

sub log {
  my($self,%arg) = @_;
  ++$self->{ $arg{log4p_level} };
}

sub howmany {
  my($self,@which) = @_;
  my $total = 0;
  $total += ($self->{$_} || 0) for @which;
  $total;
}

1;

myprog:

#! /usr/bin/perl

use warnings;
use strict;

use Log::Log4perl;

my $conf = q(
  log4perl.category.MyLogger = INFO, Screen

  log4perl.appender.Screen = Log::Log4perl::Appender::Screen
  log4perl.appender.Screen.layout = Log::Log4perl::Layout::SimpleLayout
);

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

my $l = Log::Log4perl->get_logger("MyLogger");

my $counter = Log::Log4perl::Appender->new("MyCounter");
$l->add_appender($counter);

$l->warn("warning");
$l->info("info");
$l->error("incorrect");
$l->fatal("really bad, man");

print $counter->howmany(qw/ WARN ERROR FATAL /), "\n";

exit ($counter->howmany(qw/ WARN ERROR FATAL /) ? 1 : 0);

Output:

$ ./myprog 
WARN - warning
INFO - info
ERROR - incorrect
FATAL - really bad, man
3
$ echo $?
1

Comment out the ...->warn, ...->error, and ...->fatal lines to get

$ ./myprog 
INFO - info
0
$ echo $?
0