gistfile1.txt

#!/usr/bin/env perl

use strict;
use warnings;

use AnyEvent::Socket;

use constant THROTTLE => 3;   # Number of count alert will be sent out and die
use constant INTERVAL => 60;   # Interval for polling health check
use constant COOLTIME => 600; # once host down is detected cooldown for amount of time

my ($host, $port) = @ARGV;

die "No host name is given" unless defined $host;
die "No port numb is given" unless defined $port;

my $cnt = 1; # for throttling number of alerting
my $cv  = AnyEvent->condvar;

my $once_per_second;
   $once_per_second = AnyEvent->timer(interval => INTERVAL,
				      cb       => \&port_check,
);

$cv->wait;

sub port_check {
  my $done = AnyEvent->condvar;

  tcp_connect $host, $port, sub {
    my ($fh) = @_ or do {

      my $time = localtime;
      warn "The host or service is down with [$!] at [$time]\n"; # print 'timeout' at most every second

      exit if $cnt++ == THROTTLE;

      undef $once_per_second;
            $once_per_second = AnyEvent->timer(after    => COOLTIME,
					       interval => INTERVAL,
					       cb       => \&port_check,
					);
      return;
    };

    my $time = localtime;
    warn "Host($host) is alive at [$time]";
  };
}