scripts/lcp_rtt_exporter: Prometheus exporter for the LCP RTT data

Signed-off-by: Marco d'Itri <md@linux.it>

diff --git a/scripts/lcp_rtt_exporter b/scripts/lcp_rtt_exporter
new file mode 100644 (file)
index 0000000..6fab745
--- /dev/null
+++ b/scripts/lcp_rtt_exporter
@@ -0,0 +1,108 @@
+#!/usr/bin/perl
+# vim: shiftwidth=4 tabstop=4
+#
+# This CGI program is a Prometheus exporter for pppd's lcp-rtt-file feature.
+#
+# Copyright (C) Marco d'Itri <md@linux.it>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+
+use v5.14;
+use warnings;
+use autodie;
+
+use List::Util qw(sum max min);
+
+{
+       my $data = read_data('/run/ppp-rtt.data');
+       my $stats = compute_statistics($data, 60);
+
+       my $s = metrics($stats);
+
+       print "Content-type: text/plain\n\n$s";
+       exit;
+}
+
+sub metrics {
+       my ($stats) = @_;
+
+       my $s = <<END;
+# TYPE lcp_rtt_status gauge
+# HELP LCP RTT status
+lcp_rtt_status $stats->{status}
+END
+       foreach (qw(average min max loss)) {
+               next if not exists $stats->{$_};
+               $s .= <<END;
+# TYPE lcp_rtt_$_ gauge
+# HELP LCP RTT $_
+lcp_rtt_$_ $stats->{$_}
+END
+       }
+
+       return $s;
+}
+
+sub compute_statistics {
+       my ($data, $length) = @_;
+
+       my $cutoff = time() - $length;
+       my @e = grep { $_->[0] >= $cutoff } @{ $data->{data} };
+       return { status => -1 } if not @e; # no data
+
+       my $average = (sum map { $_->[1] } @e) / scalar(@e);
+       my $min = min map { $_->[1] } @e;
+       my $max = max map { $_->[1] } @e;
+       my $loss = sum map { $_->[2] } @e;
+
+       return {
+               status  => $data->{status},
+               average => $average,
+               min             => $min,
+               max             => $max,
+               loss    => $loss,
+       };
+}
+
+sub read_data {
+       my ($file) = @_;
+
+       my $data;
+       open(my $fh, '<', $file);
+       binmode($fh);
+       my $bytes_read;
+       do {
+               $bytes_read = sysread($fh, $data, 8192, length($data));
+       } while ($bytes_read == 8192);
+       close($fh);
+
+       my ($magic, $status, $position, $echo_interval, $rest)
+               = unpack('NNNN a*', $data);
+       return undef if $magic != 0x19450425;
+
+       # the position is relative to the C array, not to the logical entries
+       $position /= 2;
+
+       my @rawdata = unpack('(N C a3)*', $rest);
+       my @data;
+       while (my ($time, $loss, $rtt) = splice(@rawdata, 0, 3)) {
+               push(@data, [ $time, unpack('N', "\000$rtt"), $loss ]);
+       }
+
+       @data =
+               # skip any "empty" (null) entries
+               grep { $_->[0] }
+               # rearrange the list in chronological order
+               (@data[$position+1 .. $#data], @data[0 .. $position]);
+
+       return {
+               status                  => $status,
+               echo_interval   => $echo_interval,
+               position                => $position,
+               data                    => \@data,
+       };
+}
+