/usr/lib/nagios/plugins/check_ajp is in nagios-plugins-contrib 14.20141104.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 | #!/usr/bin/perl -w
#
# History:
# 	2010-11-05	First release (v1)
#
# Comment: Please send bug fixes and enhancements to <rmichel@devnu11.net>
#
# check_ajp - nagios plugin for jboss monitoring
# Copyright (C) 2010  Michel Rode <rmichel@devnu11.net>
# Copyright (C) 2013  Bernd Zeimetz <b.zeimetz@conova.com>
#
# 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 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
#
# Usage: ./check_ajp --app ip.of.the.app [--port 8009 --warn 1 --crit 2 --timeout 5]
# 
use warnings;
use strict;
use Getopt::Long;
use Socket;
use Time::HiRes 'time';
use IO::Socket;
my $app = '';
my $port = '8009';
my $warntime = '1.5';
my $crittime = '3';
my $timeout = '10';
my ($sock, $time1, $time2);
my $pong = 'null';
sub conndie{
	my $msg = shift;
	print "CRITICAL : $msg\n";
	exit 2;
}
sub xdie{
	my $msg = shift;
	printf STDERR "Usage: check_ajp --app ip.of.the.app [--port 8009 --warn 1 --crit 2 --timeout 5]\n\n";
	printf STDERR "ERROR: $msg\n";
	exit 3;
}
GetOptions("app=s" => \$app, "port=s" => \$port, "warn=f" => \$warntime, "crit=f" => \$crittime, "timeout=f" => \$timeout);
if ($app eq '') {
    xdie('--app not given')
}
my $ping = pack 'C5'    # Format template.
    , 0x12, 0x34        # Magic number for server->container packets.
    , 0x00, 0x01        # 2 byte int length of payload.
    , 0x0A              # Type of packet. 10 = CPing.
;
my $expected = pack 'C5'    # Format template.
    , 0x41, 0x42            # Magic number for container->server packets.
    , 0x00, 0x01            # 2 byte int length of payload.
    , 0x09                  # Type of packet. 9 = CPong reply.
;
$time1 = time();
eval {
	local $SIG{ALRM} = sub { die "alarm\n" };
	alarm($timeout);
	$sock = IO::Socket::INET->new(Proto => "tcp",
					PeerAddr  => $app,
					PeerPort  => $port) || conndie($@);
	$sock->autoflush(1);
	print $sock $ping;
	$sock->recv($pong,5);
        close $sock;
	alarm(0);
}; 
if ($@) {
	conndie($@) unless $@ eq "alarm\n";
	$time2 = (time() - $time1);
	printf "CRITICAL - AJP - Timeout after %1.0fs\n",$time2;
	exit 2;
} else {
	$time2 = (time() - $time1);
	if ($pong eq $expected) {
		if ($time2 >= $crittime) {
			printf "CRITICAL - AJP - %3.5f seconds response time|time=%3.6fs;;;0.000000;%2.6f\n",$time2,$time2,$timeout;
			exit 2;
		} elsif ($time2 >= $warntime) {
			printf "WARNING - AJP - %3.5f seconds response time|time=%3.6fs;;;0.000000;%2.6f\n",$time2,$time2,$timeout;
			exit 1;
		} else {
		        printf "OK - AJP - %3.5f seconds response time|time=%3.6fs;;;0.000000;%2.6f\n",$time2,$time2,$timeout;
		        exit 0;
		}
	} else {
	        printf "UNKNOWN - AJP - %3.5f seconds response time|time=%3.6fs;;;0.000000;%2.6f\n",$time2,$time2,$timeout;
	        exit 3;
	}
}
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