modules/Logger.pm

   1 package Guardian::Logger;
   2 use strict;
   3 use warnings;
   4
   5 use Exporter qw(import);
   6
   7 our @EXPORT_OK = qw(New Log GetLogLevels);
   8
   9 use Sys::Syslog qw(:DEFAULT setlogsock);
  10
  11 # Hash which stores all supported log levels and their priority.
  12 my %loglevels = (
  13         'off' => '0',
  14         'err' => '1',
  15         'info' => '1',
  16         'debug' => '2',
  17 );
  18
  19 # This hash contains the supported log facilities and their corresponding subroutines.
  20 my %logfacilities = (
  21         "console" => \&LogFacilityConsole,
  22         "syslog" => \&LogFacilitySyslog,
  23 );
  24
  25
  26 #
  27 ## The "Init" (Logger) function.
  28 #
  29 ## This function is responsible to initialize the Logger as a class based object.
  30 ## It has to be called once before logging can be done.
  31 #
  32 ## The following arguments must be passed, when initializing a new Logger:
  33 ## "LogLevel" and "LogFacility" with valid values from above.
  34 #
  35 sub Init (%) {
  36         my ( $class, %args ) = @_;
  37         my $self = \%args;
  38
  39         # Fail, if some critical arguments are missing.
  40         unless ((exists($self->{LogLevel})) && (exists($self->{LogFacility}))) {
  41                 die "Could not initialize the Logger: Too less arguments are given.\n";
  42         }
  43
  44         # Use bless to make "$self" to an object of class "$class".
  45         bless($self, $class);
  46
  47         # Return the class object.
  48         return $self;
  49 }
  50
  51 #
  52 ## The main "Log" function.
  53 #
  54 ## This function is used to handle the messages which are generated on various
  55 ## points in the main programm or its modules. Those messages will contain usefull
  56 ## information or deeper details about errors.
  57 #
  58 ## The Log function takes care about the configured loglevel and transmitts the
  59 ## log messages to the configured log facility.
  60 #
  61 sub Log ($$) {
  62         my $self = shift;
  63         my ($level, $message) = @_;
  64
  65         # Check if we got an invalid loglevel.
  66         unless(exists($loglevels{$level})) {
  67                 &Log("err", "The logger has been called with an invalid loglevel ($level)!\n");
  68                 return;
  69         }
  70
  71         # Get value for the current used loglevel.
  72         my $current_level = $loglevels{$self->{LogLevel}};
  73
  74         # Get value for the required loglevel.
  75         my $required_level = $loglevels{$level};
  76
  77         # Compare the current and required level to determine,
  78         # if the message should be handled.
  79         if ($current_level >= $required_level) {
  80                 # Get the facility, which should be used.
  81                 my $use_facility = $self->{LogFacility};
  82
  83                 # Transmit log message to the correct log facility.
  84                 $logfacilities{$use_facility}->($level, $message);
  85         }
  86 }
  87
  88 #
  89 ## GetLogLevels function.
  90 #
  91 ## This really simple function just returns the hash which
  92 ## contains all supported log levels.
  93 #
  94 sub GetLogLevels () {
  95         # Nothing to do, just return the loglevels hash.
  96         return %loglevels;
  97 }
  98
  99 #
 100 ## LogFacilityConsole function.
 101 #
 102 ## This is a very simple log facility which just prints the given log
 103 ## message to STDOUT.
 104 #
 105 sub LogFacilityConsole ($$) {
 106         my ($type, $message) = @_;
 107
 108         # Print message on STDOUT.
 109         print STDOUT "\[$type\] $message\n";
 110 }
 111
 112 #
 113 ## LogFacilitySyslog function.
 114 #
 115 ## This log facility sends a given log message to the system log service (syslog).
 116 #
 117 sub LogFacilitySyslog ($$) {
 118         my ($type, $message) = @_;
 119
 120         # The syslog function works best with an array based input,
 121         # so generate one before passing the message details to syslog.
 122         my @syslog = ("$type", "<$type> $message");
 123
 124         # Establish the connection to the syslog service.
 125         openlog('guardian', 'cons,pid', 'user');
 126
 127         # Send the log message.
 128         syslog(@syslog);
 129
 130         # Close the log handle.
 131         closelog();
 132 }
 133
 134 1;