#!/usr/bin/perl
#
# metrics-emitter
#
# Run this job once. It will gather metrics on various things we need and emit
# them to our monitoring system, which is used for HorizontalPodAutoscalers
# and the like.
#
# Authors:
#      Mark Smith <mark@dreamwidth.org>
#
# Copyright (c) 2019 by Dreamwidth Studios, LLC.
#
# This program is free software; you may redistribute it and/or modify it under
# the same terms as Perl itself.  For a copy of the license, please reference
# 'perldoc perlartistic' or 'perldoc perlgpl'.
#

use v5.10;
use strict;

BEGIN {
    require "$ENV{LJHOME}/cgi-bin/ljlib.pl";
}
use Log::Log4perl;
my $log = Log::Log4perl->get_logger(__PACKAGE__);

use Time::HiRes qw/ time sleep /;

use DW::Stats;
use DW::TaskQueue::SQS;

my $q = DW::TaskQueue::SQS->init(%LJ::SQS);

my $next_get_attributes = time();

while (1) {

    # Ensure we run as close to every 10 seconds as we can, no matter how long it
    # takes to talk to AWS etc
    my $sleep_for = $next_get_attributes - time();
    sleep($sleep_for) if $sleep_for > 0;
    $next_get_attributes += 10;

    $log->info('Metrics emitter fetching metrics.');

    my $qattrs = $q->queue_attributes;
    foreach my $queue ( keys %$qattrs ) {
        my $messages = $qattrs->{$queue}->ApproximateNumberOfMessages;

        $log->info(' * Queue ', $queue, ' depth: ', $messages, ' messages' );

        DW::Stats::gauge(
            'dw.sqs.approx_messages',
            $messages,
            [ 'queue:' . $queue ]
        );
    }
}