Consul two-stage check prototype

consulcheck.pl

#!/usr/bin/env perl

use 5.014;
use warnings;
use strict;

use Consul;
use Sys::Hostname;
use Try::Tiny;

my ($service, $interval) = @ARGV;
unless ($service && $interval) {
    say "usage: check.pl <service> <interval>";
    exit 2;
}

my $node = hostname;
exit do_check($node, $service, $interval, sub { connect_check("127.0.0.1", 22) });

sub do_check {
    my ($node, $service, $interval, $check_cb) = @_;

    my $now = time;
    say "Running check for $node/$service, interval $interval, now ".scalar localtime $now;

    my $kv = Consul->new->kv;
    my $kvpath = "fm/checks/$node/$service";

    my $mark = try {
        $kv->get("$kvpath/mark");
    }
    catch {
        if (m/^404/) {
            say "$kvpath/mark not found, assuming marked up";
            return;
        }
        say "Couldn't get mark $kvpath/mark: $_";
        return 2;
    };
    return $mark if defined $mark && !ref $mark;

    if ($mark && $mark->value eq "down") {
        say "$node/$service marked down";
        return 2;
    }

    my $lastrun = try {
        $kv->get("$kvpath/lastrun");
    }
    catch {
        if (m/^404/) {
            # never run before
            return; # from try
        }
        say "Couldn't get last run time $kvpath/lastrun $_";
        return 2;
    };
    return $lastrun if defined $lastrun && !ref $lastrun;

    if ($lastrun && ($lastrun->value + $interval) > $now) {
        my $lastresult = try {
            $kv->get("$kvpath/lastresult");
        }
        catch {
            if (m/^404/) {
                # never run before
                return; # from try
            }
            say "Couldn't get last result $kvpath/lastresult: $_";
            return 2;
        };
        return $lastresult if defined $lastresult && !ref $lastresult;

        if ($lastresult) {
            say "Cached result, last run was ".($now-$lastrun->value)."s ago";
            return $lastresult->value;
        }
    }

    my $rc = try {
        $check_cb->();
    }
    catch {
        say "Check callback died: $_";
        2;
    };

    try {
        $kv->put("$kvpath/lastrun", $now);
    }
    catch {
        say "Couldn't save last run time $kvpath/lastrun $_";
    };

    try {
        $kv->put("$kvpath/lastresult", $rc);
    }
    catch {
        say "Couldn't save last result $kvpath/lastresult $_";
    };

    return $rc;
}

sub connect_check {
    my ($ip, $port) = @_;

    use IO::Socket::INET;

    my $s = IO::Socket::INET->new(
        PeerAddr => $ip,
        PeerPort => $port,
        Proto    => 'tcp',
        Timeout  => 2,
    );
    unless ($s) {
        say "Connect to port $ip:$port failed: $!";
        return 2;
    }

    return 0;
}