Re: [log4perl-devel] How to get Log4Perl to switch logfiles

[Mike S. <msc...@ao...>]

Simon Taylor wrote on 10/29/2003, 2:48 PM:

 > The logger resets the filename so I should get a new log for each job.

I'm assuming by "job" you mean a call within the same (Unix) process -- 
correct?

 > The logger is then saved as part of the object

Actually, loggers should *never* be saved in objects or elsewhere. You 
can always obtain them cheaply by calling get_logger("category"). This 
way, you're safe to change the configuration on the fly without ending 
up with stale loggers.

 > Log4PerlInit - is called from Config.
 > SelfLog is used when i want to get the Config module to log to the
 > same file as the module that called Log4PerlInit

Not quite sure why you have two different functions -- there's a lot of 
code duplication between the two. Hopefully, you'll like the approach 
outlined further down.

 > Whats the best way to undef all the loggers at each job change. Or put
 > another way when running a long job how do I safely get log4perl to
 > switch to a new log appender and stop using the old one

I won't suggest to call Log4perl's init() on every job, although that 
would probably work for your scenario.

Unfortunately, our current file appender doesn't have a "switch_file" 
method. So, for now, you could create a new file appender class, inherit 
from L4p::Appender::File and define a switch_file method, blatently 
making use of L4p::Appender::File's private data:

##################################################
package ReopeningFileAppender;
##################################################
use warnings;
use strict;
use base qw(Log::Log4perl::Appender::File);

##################################################
sub switch_file {
##################################################
     my($self, $newname) = @_;

     undef $self->{fh};
     $self->{filename} = $newname;
     my $arrows = ">";

     if($self->{mode} eq "append") {
         $arrows = ">>";
     }
     my $fh = do { local *FH; *FH; };
     open $fh, "$arrows$self->{filename}" or
         die "Can't open $self->{filename} ($@)";
     $self->{fh} = $fh;
}
1;

__END__

If you put that code into ReopeningFileAppender.pm and define a 
configuration file l4p.conf like

# l4p.conf
log4perl.logger = DEBUG, APP1
log4perl.appender.APP1=ReopeningFileAppender
log4perl.appender.APP1.layout    = Log::Log4perl::Layout::SimpleLayout
log4perl.appender.APP1.filename  = test.log

then your code is free to do something like

   Log::Log4perl->init("l4p.conf");
   DEBUG("logged to test.log");

       # Get appender and switch file on it
   my $app = Log::Log4perl::appenders()->{APP1};
   $app->switch_file("foobar.log");
   DEBUG("logged to foobar.log");

which first logs to test.log, then obtains the appender and causes it to 
  flush its buffer to the old file and open a new one.
Again, not pretty, because it assumes L4p::Appender::File isn't changing 
its private 'fh' handle, but for the next version, I might add a 
switch_file() method to our file appender.

-
-- Mike
Mike Schilli
m...@pe...