Accessing Log::Log4perl Configuration Values

valdez has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

Log::Log4perl is my preferred tool for logging and this time I want to access some values of its configuration from another application. I've read the documentation, but I didn't find any suitable method; so I started from parsing a configuration file, but very soon I realized that I also needed the variable expansion feature provided by Log4perl; after that I dived into the source and came back with the following class to accomplish the task:

package Log::Log4perl::Config::Standalone;

use Log::Log4perl::Config;
use Log::Log4perl::Config::PropertyConfigurator;
use Carp;

sub new {
  my ($class, $filename) = @_;

  confess "configuration '$filename' not found\n" unless -f $filename;

  my $cp = Log::Log4perl::Config::PropertyConfigurator->new;
  $cp->file( $filename );

  my $self = {
    data => $cp->parse()
  };

  return bless $self, $class;
}

sub value {
  my ($self, $path, $default) = @_;

  my @p = split /\./, $path;

  shift @p if $p[0] eq 'log4perl';

  my $found = 1;
  my $r = $self->{data};
  while (my $n = shift @p) {
    if (exists $r->{$n}) {
      $r = $r->{$n};
    }
    else {
      $found = 0;
    }
  }

  return $found ? $r->{value} : $default;
}

1;

__END__
[download]

Given the following configuration file:

# filename: l4p.conf
global_var = /var/log/some/file.log

log4perl.rootLogger = DEBUG, LOGFILE
log4perl.appender.LOGFILE = Log::Log4perl::Appender::File
log4perl.appender.LOGFILE.filename = ${global_var}
log4perl.appender.LOGFILE.mode = append
log4perl.appender.LOGFILE.layout = PatternLayout
log4perl.appender.LOGFILE.layout.ConversionPattern = %d{ISO8601} [%P] 
+%C %p %m%n
[download]

this code retrieves a value:

use Log::Log4perl::Config::Standalone;

my $c = Log::Log4perl::Config::Standalone->new('./l4p.conf');
print $c->value('log4perl.appender.LOGFILE.filename'), "\n";
[download]

What do you think about it? How would you solve the same problem?

Thanks, Valerio

Comment on Accessing Log::Log4perl Configuration Values Select or Download Code

Replies are listed 'Best First'.
Re: Accessing Log::Log4perl Configuration Values by andyford (Curate) on Mar 18, 2007 at 18:03 UTC
If you're willing to go back and redo your configs in XML, Log::Log4perl::Config::DOMConfigurator looks to be tailor made for you. non-Perl: Andy Ford	[reply]
Re^2: Accessing Log::Log4perl Configuration Values by valdez (Monsignor) on Mar 19, 2007 at 07:56 UTC
Thank you andyford, but Log::Log4perl::Config::DOMConfigurator has the same problem of Log::Log4perl::Config::PropertyConfigurator: it cannot be used standalone to access configuration values and, when used with Log::Log4perl::Config, returns an hash reference. This is why I wrote that small package. Ciao, Valerio	[reply]
Re^3: Accessing Log::Log4perl Configuration Values by andyford (Curate) on Mar 19, 2007 at 09:39 UTC
Sorry I should have explained my thoughts in more detail. What I'm thinking is that your write your log4perl configs in XML. Log::Log4perl::Config::DOMConfigurator is used in your perl programs that are actually using Log::Log4perl. Then when you want to get at your config elements from somewhere else, you parse the XML with a DTD and an XML parser. That buys you a clean way to get at everything in the log4perl configs. Of course this is a lot of work and it may be overkill for your needs. However it does "future-proof" you in the case of later requirements causing your home grown parsing to become unwieldy or hard to maintain. non-Perl: Andy Ford	[reply]
Re^4: Accessing Log::Log4perl Configuration Values by valdez (Monsignor) on Mar 19, 2007 at 11:51 UTC
Re^5: Accessing Log::Log4perl Configuration Values by andyford (Curate) on Mar 19, 2007 at 15:14 UTC
Re: Accessing Log::Log4perl Configuration Values by whereiskurt (Friar) on Mar 18, 2007 at 19:07 UTC
I'm feeling some sort of 'O'Reilly tribute' <Saint Patty's just passed> Happy St. Patty's (I'm actually a tad late, somewhere) I have always found that to be an excellent log4perl article series, but as I refer to it I can't seem to see any reference to it. Here's a better source: Variable Substitution (are you not a troll? :L) " To avoid having to retype the same expressions over and over again, Log::Log4perl's configuration files support simple variable substitution. New variables are defined simply by adding `varname = value` [download] lines to the configuration file before using `${varname}` [download] afterwards to recall the assigned values. Here's an example: layout_class = Log::Log4perl::Layout::PatternLayout layout_pattern = %d %F{1} %L> %m %n log4perl.category.Bar.Twix = WARN, Logfile, Screen log4perl.appender.Logfile = Log::Log4perl::Appender::File log4perl.appender.Logfile.filename = test.log log4perl.appender.Logfile.layout = ${layout_class} log4perl.appender.Logfile.layout.ConversionPattern = ${layout_patt +ern} log4perl.appender.Screen = Log::Log4perl::Appender::Screen log4perl.appender.Screen.layout = ${layout_class} log4perl.appender.Screen.layout.ConversionPattern = ${layout_patte +rn} [download] This is a convenient way to define two appenders with the same layout without having to retype the pattern definitions. Update: After rereading your post (I tend to do that) I think that perhaps this more inline with what you're getting at. This is analagous to writing log4perl eval statment - pick your favourite Templater for flavour. Kurt Dirty Tricks Example (Sorry about the Troll comment :)) A simple example to cut-and-paste and get started: `use Log::Log4perl qw(get_logger); my $conf = q( log4perl.category.Bar.Twix = WARN, Logfile log4perl.appender.Logfile = Log::Log4perl::Appender::File log4perl.appender.Logfile.filename = test.log log4perl.appender.Logfile.layout = \ Log::Log4perl::Layout::PatternLayout log4perl.appender.Logfile.layout.ConversionPattern = %d %F{1} %L> +%m %n ); Log::Log4perl::init(\$conf); my $logger = get_logger("Bar::Twix"); $logger->error("Blah");` [download] This will log something like: `2002/09/19 23:48:15 t1 25> Blah` [download] to the log file 'test.log', which Log4perl will append to or create it if it doesn't exist already.	[reply] [d/l] [select]
Re^2: Accessing Log::Log4perl Configuration Values by valdez (Monsignor) on Mar 19, 2007 at 11:41 UTC
Ciao whereiskurt, I know how to use Log4perl configuration files :)) The problem was different, let me rephrase it: I want to access l4p configuration values from outside l4p itself, how? An home-made parser is not the solution, as I should implement also variable substitution; on the other side, l4p Config classes are not so friendly. Now, I'm asking myself if the way I used the Log4perl classes is correct or not. Thanks, Valerio	[reply]
Re^3: Accessing Log::Log4perl Configuration Values by whereiskurt (Friar) on Mar 19, 2007 at 15:45 UTC
Valerio, after looking at your home node it's pretty clear that you would know how to use log4perl :) <kneels humbly> I wonder how you moved forward on this problem? It would seem there are only two ways to go: either you're building a config on the fly and using the log4perl::init call, or you're letting log4perl parse through a config already made and working with the log4perl->value madness. :) I wonder <outloud apparently> if slupring the 'l4p.conf' and munging it might really be your best option? I suspect that the variable substitution wouldn't be that tricky afterall... regards! Kurt PS: I realise that you said *do not* want yet another home made parser but here's one just incase anyone was interested (or incase you changed your mind :))	[reply]
Re^4: Accessing Log::Log4perl Configuration Values by valdez (Monsignor) on Mar 19, 2007 at 18:49 UTC
Re^2: Accessing Log::Log4perl Configuration Values by TomDLux (Vicar) on Jul 20, 2010 at 20:38 UTC
Patty is a girl. Like Patty Hearst, for example, machine-gun and all. An Irish Patrick is Paddy. -- `TTTATCGGTCGTTATATAGATGTTTGCA`	[reply]
Re: Accessing Log::Log4perl Configuration Values by saintmike (Vicar) on Mar 21, 2007 at 06:22 UTC
Actually, Log::Log4perl already offers access to certain parts of the configuration: You can find appenders by name via `Log::Log4perl->appender_by_name`, for example. Make sure to read the explanation in the manual for this. If you're just after the name of a file used by a file appender, that'd be the route I'd recommend for you to use. If you're after a custom appender, there's an FAQ for that. If you need anything else, just let me know what it is you're after, and if it's of general interest, I can put it into Log::Log4perl for you.	[reply]


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