Re: [log4perl-devel] Config file reload on signal

[Kevin G. <ke...@go...>]

That's a pretty neat idea, go for it, dude!

msc...@ao... wrote:
> Hey,
> 
> just had an idea: How about if we add functionality to init_and_watch in Log::Log4perl to not only watch config files but to also be able to listen to (Unix) signals instead? Yeah, yeah, I know signals are unreliable and can cause all kinds of crazy stuff -- but how about if we have the signal handler just set a global variable, which is checked by the watcher code instead of calling time() all the time?
> Please take a look at the patch below, and let me know what you think ... the addtl. syntax is:
> 
>    init_and_watch($file, 'HUP'); # will listen to SIGHUP
> 
> I've also attached a test file.
> 
> -- Mike
> 
> ############################
> # Mike Schilli             #
> # log...@pe... #
> # http://perlmeister.com   #
> # log4perl.sourceforge.net #
> ############################
> 
> 
> ------------------------------------------------------------------------
> 
> Index: lib/Log/Log4perl/Config.pm
> ===================================================================
> RCS file: /cvsroot/log4perl/Log-Log4perl/lib/Log/Log4perl/Config.pm,v
> retrieving revision 1.52
> diff -a -u -r1.52 Config.pm
> --- lib/Log/Log4perl/Config.pm	20 Jul 2003 20:24:18 -0000	1.52
> +++ lib/Log/Log4perl/Config.pm	4 Aug 2003 04:47:28 -0000
> @@ -45,10 +45,16 @@
>  sub init_and_watch {
>  ###########################################
>      my ($class, $config, $delay) = @_;
> +        # delay can be a signal name - in this case we're gonna
> +        # set up a signal handler.
>  
>      if(defined $WATCHER) {
>          $config = $WATCHER->file();
> -        $delay  = $WATCHER->check_interval();
> +        if(defined $Log::Log4perl::Config::Watch::SIGNAL_CAUGHT) {
> +            $delay  = $WATCHER->signal();
> +        } else {
> +            $delay  = $WATCHER->check_interval();
> +        }
>      }
>  
>      print "init_and_watch ($config-$delay). Resetting.\n" if DEBUG;
> @@ -57,8 +63,6 @@
>  
>      defined ($delay) or $delay = $DEFAULT_WATCH_DELAY;  
>  
> -    $delay =~ /\D/ && die "illegal non-numerical value for delay: $delay";
> -
>      if (ref $config) {
>          die "Log4perl can only watch a file, not a string of " .
>              "configuration information";
> @@ -66,10 +70,17 @@
>          die "Log4perl can only watch a file, not a url like $config";
>      }
>  
> -    $WATCHER = Log::Log4perl::Config::Watch->new(
> -                      file           => $config,
> -                      check_interval => $delay,
> -               );
> +    if($delay =~ /\D/) {
> +        $WATCHER = Log::Log4perl::Config::Watch->new(
> +                          file   => $config,
> +                          signal => $delay,
> +                   );
> +    } else {
> +        $WATCHER = Log::Log4perl::Config::Watch->new(
> +                          file           => $config,
> +                          check_interval => $delay,
> +                   );
> +    }
>  
>      _init($class, $config);
>  }
> Index: lib/Log/Log4perl/Logger.pm
> ===================================================================
> RCS file: /cvsroot/log4perl/Log-Log4perl/lib/Log/Log4perl/Logger.pm,v
> retrieving revision 1.55
> diff -a -u -r1.55 Logger.pm
> --- lib/Log/Log4perl/Logger.pm	4 Aug 2003 02:37:35 -0000	1.55
> +++ lib/Log/Log4perl/Logger.pm	4 Aug 2003 04:47:30 -0000
> @@ -292,13 +292,14 @@
>  
>      if (defined $Log::Log4perl::Config::WATCHER) {
>  
> -        $watch_code = <<'EOL';
> -        my($logger, $subname) = @_;
> -        if(time() > $Log::Log4perl::Config::Watch::NEXT_CHECK_TIME and
> -           $Log::Log4perl::Config::WATCHER->change_detected()) {
> +        my $cond = generate_watch_conditional();
> +
> +        $watch_code = <<EOL;
> +        my(\$logger, \$subname) = \@_;
> +        if($cond) {
>              Log::Log4perl->init_and_watch();
>              # Forward call to new configuration
> -            return $logger->$subname();
> +            return \$logger->\$subname();
>          }
>  EOL
>      }
> @@ -317,20 +318,36 @@
>  ##################################################
>      print "generate_watch_code:\n" if DEBUG;
>  
> -    return <<'EOL';
> +    my $cond = generate_watch_conditional();
> +
> +    return <<EOL;
>          print "exe_watch_code:\n" if DEBUG;
>                         
>          # more closures here
> -        if(time() > $Log::Log4perl::Config::Watch::NEXT_CHECK_TIME and
> -           $Log::Log4perl::Config::WATCHER->change_detected()) {
> +        if($cond) {
>              Log::Log4perl->init_and_watch();
>                         
> -            my $methodname = lc($level);
> -            $logger->$methodname(@_); # send the message
> -                                      # to the new configuration
> +            my \$methodname = lc(\$level);
> +            \$logger->\$methodname(\@_); # send the message
> +                                         # to the new configuration
>              return;        #and return, we're done with this incarnation
>          }
>  EOL
> +}
> +
> +##################################################
> +sub generate_watch_conditional {
> +##################################################
> +
> +    if(defined $Log::Log4perl::Config::Watch::SIGNAL_CAUGHT) {
> +        # In this mode, we just check for the variable indicating
> +        # that the signal has been caught
> +        return q{$Log::Log4perl::Config::Watch::SIGNAL_CAUGHT};
> +    }
> +
> +    # In this mode, we check if the config file has been modified
> +    return q{time() > $Log::Log4perl::Config::Watch::NEXT_CHECK_TIME 
> +              and $Log::Log4perl::Config::WATCHER->change_detected()};
>  }
>  
>  ##################################################
> Index: lib/Log/Log4perl/Config/Watch.pm
> ===================================================================
> RCS file: /cvsroot/log4perl/Log-Log4perl/lib/Log/Log4perl/Config/Watch.pm,v
> retrieving revision 1.3
> diff -a -u -r1.3 Watch.pm
> --- lib/Log/Log4perl/Config/Watch.pm	20 Jul 2003 20:24:01 -0000	1.3
> +++ lib/Log/Log4perl/Config/Watch.pm	4 Aug 2003 04:47:30 -0000
> @@ -8,6 +8,7 @@
>  use constant DEBUG => 0;
>  
>  our $NEXT_CHECK_TIME;
> +our $SIGNAL_CAUGHT;
>  
>  ###########################################
>  sub new {
> @@ -16,6 +17,7 @@
>  
>      my $self = { file            => "",
>                   check_interval  => 30,
> +                 signal          => undef,
>                   %options,
>                   _last_checked_at => 0,
>                   _last_timestamp  => 0,
> @@ -23,8 +25,15 @@
>  
>      bless $self, $class;
>  
> -        # Just called to initialize
> -    $self->change_detected();
> +    if($self->{signal}) {
> +            # We're in signal mode, set up the handler
> +        $SIG{$self->{signal}} = sub { $SIGNAL_CAUGHT = 1; };
> +            # Reset the marker. The handler is going to modify it.
> +        $SIGNAL_CAUGHT = 0;
> +    } else {
> +            # Just called to initialize
> +        $self->change_detected();
> +    }
>  
>      return $self;
>  }
> @@ -35,6 +44,14 @@
>      my($self) = @_;
>  
>      return $self->{file};
> +}
> +
> +###########################################
> +sub signal {
> +###########################################
> +    my($self) = @_;
> +
> +    return $self->{signal};
>  }
>  
>  ###########################################

-- 
Happy Trails . . .

Kevin M. Goess
(and Anne and Frank)
904 Carmel Ave.
Albany, CA  94706
(510) 525-5217