#!/usr/bin/perl
# $Id$
# http://poe.perl.org/?POE_Cookbook/Watching_Logs

use warnings;
use strict;

use POE qw( Wheel::FollowTail );

my %logs_to_watch;                                        # new stuff
my %filter_lookup;                                        # new stuff
my %record_hash;                                          # new stuff

# Read list of things to watch and filter to use
#
# my %logs_to_watch =           | fileidx     fullpath
# {                             | --------    --------------------
#  cron =>"/var/log/cron",      | file0000 => '/var/log/cron'
#  mail =>"/var/log/maillog",   | file0001 => '/var/log/maillog'
#  ppp  =>"/var/log/ppp.log",   | file0002 => '/var/log/ppp.log'
#  httpd=>"/var/log/httpd.log", | file0003 => '/var/log/httpd.log'
#  msg  =>"/var/log/message",   | file0004 => '/var/log/message'
#  myfilter=>"mylogfile1",      | file0005 => 'mylogfile1'
# };                            |

&read_watchlist(\%logs_to_watch, \%filter_lookup);

# Start a session to watch the logs.

POE::Session->create
  ( inline_states =>
      { _start => \&begin_watchers,

        # Handle records from each log differently.
#       cron_record  => \&cron_got_record,                # old stuff
#       mail_record  => \&mail_got_record,                # old stuff
#       ppp_record   => \&ppp_got_record,                 # old stuff
#       httpd_record => \&httpd_got_record,               # old stuff
#       msg_record   => \&msg_got_record,                 # old stuff

        %record_hash,                                     # new stuff

        # Handle log resets and errors the same way for each file.
        log_reset   => \&generic_log_reset,
        log_error   => \&generic_log_error,
    alarm_reset => \&alarm_reset,
      }
  );

sub alarm_reset {
  my ($kernel, $heap) = @_[KERNEL, HEAP];
  print "alarm reset ...\n";

  if ( exists $heap->{'alarm'} ) {
    delete $heap->{'services'};
    delete $heap->{'watchers'};
    $kernel->delay_add("alarm_reset", 10);
    $kernel->yield('start');
  }
  else {
    $kernel->delay("alarm_reset", 10);
  }
}

sub begin_watchers {
    my ($kernel, $heap) = @_[KERNEL, HEAP];

    while ( my ( $service, $log_file ) = each %logs_to_watch ) {
        my $log_watcher = POE::Wheel::FollowTail->new
          ( Filename => $log_file,
            InputEvent => $service . "_record",
            ResetEvent => "log_reset",
            ErrorEvent => "log_error",
          );

        $heap->{services}->{ $log_watcher->ID } = $service;
        $heap->{watchers}->{ $log_watcher->ID } = $log_watcher;
    }
    $kernel->yield('alarm_reset');
}

# Handle log resets the same way for each file.  Simply recognize that
# the log file was reset.

sub generic_log_reset {
    my ( $heap, $wheel_id ) = @_[ HEAP, ARG0 ];

    my $service = $heap->{services}->{$wheel_id};
    print "--- $service log reset at ", scalar(gmtime), " GMT\n";
}

# Handle log errors the same way for each file.  Recognize that an
# error occurred while watching the file, and shut the watcher down.
# If this were a real log watcher, it would periodically try to resume
# watching the log file.

sub generic_log_error {
    my ( $heap, $operation, $errno, $error_string, $wheel_id ) =
      @_[ HEAP, ARG0, ARG1, ARG2, ARG3 ];

    my $service = $heap->{services}->{$wheel_id};
    print "--- $service log $operation error $errno: $error_string\n";
    print "--- Shutting down $service log watcher.\n";

    delete $heap->{services}->{$wheel_id};
    delete $heap->{watchers}->{$wheel_id};
}

sub read_watchlist                                        # new stuff
{                                                         # new stuff
  my $paths_hash   = shift;   # \%logs_to_watch           # new stuff
  my $filters_hash = shift;   # \%filter_lookup           # new stuff
                                                          # new stuff
  open FH, "watchlist" or die "Cannot find watchlist";    # new stuff
  my $fnum = 0;                                           # new stuff
  while ( <FH> )                                          # new stuff
# while ( <DATA> )                                        # new stuff
  {                                                       # new stuff
    chomp;                                                # new stuff
    next if ! /\S/ || /^#/;                               # new stuff
    my $fileindex = sprintf "file%04d", $fnum++;          # new stuff
    my ($fullpath, $filter) = (split ' ')[0..1];          # new stuff
    print "$fileindex : $fullpath : $filter\n";           # new stuff
                                                          # new stuff
    $$paths_hash  {$fileindex} = $fullpath;               # new stuff
    $$filters_hash{$fileindex} = $filter;                 # new stuff
  }                                                       # new stuff
  close FH;                                               # new stuff

  # Save entries to %record_hash for use in POE::Session->create

  foreach ( keys %$paths_hash )                           # new stuff
  {                                                       # new stuff
    my $key  = $_ . "_record";                            # new stuff
    my $data = '\&' . $$filters_hash{$_} . "_got_record"; # new stuff
                                                          # new stuff
    $record_hash{$key} = eval($data);                     # new stuff
  }                                                       # new stuff
}                                                         # new stuff

# Filters for each log file ( shortened to save space )

sub cron_got_record {
    my $log_record = $_[ARG0];
    print "cron: ";
    print "$log_record\n";
}

sub mail_got_record {
    my $log_record = $_[ARG0];
    print "mail: ";
    print "$log_record\n";
}

sub ppp_got_record {
    my $log_record = $_[ARG0];
    print "ppp: ";
    print "$log_record\n";
}

sub httpd_got_record {
    my $log_record = $_[ARG0];
    print "http: ";
    print "$log_record\n";
}

sub msg_got_record {
    my $log_record = $_[ARG0];
    print "msg: ";
    print "$log_record\n";
}

sub myfilter_got_record {
    my $log_record = $_[ARG0];
    print "myfilter: ";
    print "$log_record\n";
}

sub reread_got_record {
    my $log_record = $_[ARG0];
    print "reread: ";
    print "$log_record\n";

    &read_watchlist (\%logs_to_watch, \%filter_lookup);
}

# Run the watchers.  The run() method will return after all the
# watchers end.

$poe_kernel->run();

__DATA__
# copy following into file "watchlist"
# fullpath                  filter
# ------------------------  ---------
/var/log/cron               cron
/var/log/maillog            mail
/var/log/ppp.log            ppp
/var/log/httpd-access.log   httpd
/var/log/messages           msg
mylogfile                   myfilter
configfile.log              reread
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