#!/usr/bin/perl

=head1 NAME

acng - Graph activity for Apt-Cacher NG, request count and bytes

=head1 APPLICABLE SYSTEMS

Systems with "Apt-Cacher NG" installed and running.

=head1 DESCRIPTION

This plugin will add graphs for "bytes in and out" and "requests in
and out" for systems with "Apt-Cacher NG" installed.

=head1 CONFIGURATION

The plugin must have permission to read the log of Apt-Cacher NG.  (On
Debian 8, this file is world readable by default).

The path to the logfile can be set with the "logfile" environment
variable.

=head2 DEFAULT CONFIGURATION

  [acng]
    env.logfile /var/log/apt-cacher-ng/apt-cacher.log

=head1 USAGE

Link this plugin to /etc/munin/plugins/ and restart the munin-node.

=head1 MAGIC MARKERS

  #%# family=contrib
  #%# capabilities=autoconf

=head1 AUTHOR

Stig Sandbeck Mathisen

=head1 LICENSE

GPLv3

=cut

use strict;
use warnings;
use Munin::Plugin;

use Storable qw(nfreeze thaw);
use MIME::Base64;

my $logfile = $ENV{'logfile'} ||= '/var/log/apt-cacher-ng/apt-cacher.log';

need_multigraph;

# Read or initialize state used by the log tailer, and the plugin.
sub read_state {

    my ($pos, $statsin) = restore_state;
    my $stats = thaw(decode_base64 $statsin) if $statsin;

    $pos = 0 unless defined $pos;
    $stats = {} unless defined $stats;

    return ($pos, $stats);
}

# Write state.
#
# "pos" is logfile position, and "stats" is a data structure with
# counters used by the plugin.
#
# Note: Munin::Plugin::save_state has limited functionality, so the
# data structure is serialized and converted to plain text.
sub write_state {
    my ($pos, $stats) = @_;

    my $statsout = encode_base64 nfreeze($stats);
    save_state($pos, $statsout);
}

sub parse_logfile {
    my $logfile = shift;
    my ($pos, $stats) = read_state;

    my @keys = ( 'time', 'direction', 'size', 'client', 'file' );

    # Open log
    my ( $fh, $reset ) = tail_open( $logfile, $pos );

    die "Unable to open logfile\n" unless ($fh);

    while (<$fh>) {
        chomp;
        my @values = split( /\|/, $_ );

        my %logentry;
        @logentry{@keys} = @values;

        $stats->{'bytes'}{ $logentry{'direction'} } += $logentry{'size'};
        $stats->{'requests'}{ $logentry{'direction'} }++;
    }

    # Close log
    $pos = tail_close($fh);

    write_state($pos, $stats);

    return $stats;
}

sub print_autoconf{
    my $logfile = shift;
    if ( open(my $fh, '<', $logfile) ) {
        print "yes\n";
    }
    else {
        printf "no (could not open %s)\n", $logfile;
    }
}

sub print_config{
    my $stats = shift;

    print << 'EOC';
multigraph acng_bytes
graph_title Apt-Cacher NG bytes
graph_order origin client
graph_vlabel bytes per ${graph_period}
graph_info Bytes transferred between origin, apt-cacher-ng and clients
origin.info bytes transferred between origin and apt-cacher-ng
origin.label origin
origin.type DERIVE
origin.min 0
client.info bytes transferred between apt-cacher-ng and clients
client.label client
client.type DERIVE
client.min 0
EOC
    print << "EOV" if $ENV{'MUNIN_CAP_DIRTYCONFIG'};
origin.value $stats->{bytes}{I}
client.value $stats->{bytes}{O}
EOV

    print << 'EOC';

multigraph acng_requests
graph_title Apt-Cacher NG requests
graph_order origin client
graph_vlabel requests per ${graph_period}
graph_info Requests from clients to apt-cacher-ng, and from apt-cacher-ng to origin
origin.info requests from apt-cacher-ng to origin
origin.label origin
origin.type DERIVE
origin.min 0
client.info requests from clients to apt-cacher-ng
client.label client
client.type DERIVE
client.min 0
EOC

    print << "EOV" if $ENV{'MUNIN_CAP_DIRTYCONFIG'};
origin.value $stats->{requests}{I}
client.value $stats->{requests}{O}
EOV

}

sub print_values{
    my $stats = shift;

    print << "EOV";
multigraph acng_bytes
origin.value $stats->{bytes}{I}
client.value $stats->{bytes}{O}

multigraph acng_requests
origin.value $stats->{requests}{I}
client.value $stats->{requests}{O}
EOV
}

if ($ARGV[0] and $ARGV[0] eq 'autoconf') {
    print_autoconf($logfile);
}
elsif ($ARGV[0] and $ARGV[0] eq 'config') {
    my $stats = parse_logfile($logfile);
    print_config($stats);
}
else {
    my $stats = parse_logfile($logfile);
    print_values($stats);
}