Use Log4Perl in sub routine?

Question

If I make an abstraction function with Log4Perl inside, then it will output the line number where the $logger->error_die($m) line is, and not where the fatalError() function is.

sub fatalError {
    my $m = shift;
    email($m, $c->{subject});
    unlink $c->{lock};
    $logger->error_die($m);
}

fatalError("Directory $d ...");

In Bash have I solved the problem by writing [###] at the end of each error message, and parse the Bash script after wards to replace [###] with unique numbers. That way I knew exactly where the error output were from. However it is not optimal to have a second script modify your source code.

Question

Is there a way to have Log4Perl to write the line number where my fatalError() function were called, or how should the problem be solved?

score 3 · Answer 1 · answered Jul 30 '14 at 13:56

You can use caller to get the details for the level above the subroutine.

However, you can also call the Log4perl methods with code refs. You do the extra processing you want and return the message you like:

$logger->error_die( sub { ... do some stuff ...; $log_message } );

For the email bit, I think I'd add another appender to handle that.

Eric Redon · Accepted Answer · 2014-07-30T16:16:27.153

The easy way is to add this line to your fatalError method:

local $Log::Log4perl::caller_depth++;

This will make Log4perl "skip" the current subroutine from the caller context.

Alternatively, if you have many such wrapper methods, encapsulate them in a single package, and register them with Log4perl like this:

Log::Log4perl->wrapper_register('My::Logger');

This topic is covered in the Log::Log4perl documentation.

tjd · Answer 3 · 2014-07-30T13:53:36.617

1

It strikes me that if you used an additional appender of a class like Log::Dispatch::Email or friends and bound it to either the ERROR or FATAL levels, and did the unlink in a subroutine referenced by either $SIG{__DIE__} or the DESTROY method of $c's class, then your sub fatalError would become unnecessary, thus solving your problem.

edited Jul 30 '14 at 13:53

answered Jul 30 '14 at 13:47

tjd

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score 1 · Answer 4 · answered Jul 30 '14 at 13:58

From what I can tell from peeking at Log4Perl's source code, it looks like it honors the warn/die convention of only appending location information to messages that don't end in a newline. That means that you can add the location via your function and stop Log4Perl from appending it:

sub fatalError {
    my $m = shift;
    my (undef, $file, $line) = caller;
    my $at = " at $file line $line.\n";
    email($m, $c->{subject});
    unlink $c->{lock};
    $logger->error_die($m . $at);
}

Use Log4Perl in sub routine?

4 Answers4