So, I set off to write the Perl version of such a monitor, but before I did I needed a simple script outside the Netscaler for debugging purposes – having to rely on the monitor for testing is needlessly cumbersome, better to get it functioning first and then add it to the monitor code later.  Also, because of that approach, the script is perfectly usable as a generic test and is written almost entirely as a self-contained sub-routine (anyone that has seen the user monitor structure on the Netscaler will instantly recognize that also).  Hence, I think it would be very easy to add the subroutine to a syslog or other monitoring type script.  Therefore I decided to share the more generic version here.  The full code is after the jump, if you prefer a more compressed binary version you can find it here: ajp.pl.gz

I have the acknowledgements in the code also, but to get them in before the jump, they were invaluable:

• The hex values are based on the information from http://tomcat.apache.org/connectors-doc/ajp/ajpv13a.html#Packet%20Headers
• Actual pack code to create the hex packets is from http://it-nonwhizzos.blogspot.com/2009/05/ajp-ping-in-perl.html

Perl Code:

#!/usr/bin/perl -w

# This is a simple Perl Script to ping and AJP server and print the response
# written as a sub-routine for easy embedding elsewhere
#

# Author: Adam Comerford (http://comerford.cc)
#
# For more information see: The Apache Tomcat Connector - AJP Protocol Reference - http://tomcat.apache.org/connectors-doc/ajp/ajpv13a.html

# Acknowledgements:
# The hex values are based on the information from http://tomcat.apache.org/connectors-doc/ajp/ajpv13a.html#Packet%20Headers
# Actual pack code to create the hex packets is from http://it-nonwhizzos.blogspot.com/2009/05/ajp-ping-in-perl.html

use strict;
use IO::Socket::INET;

my $result = ajp_probe($ARGV[0], $ARGV[1], $ARGV[2], $ARGV[3]);
print "$result \n";

sub ajp_probe {

        # flush after every write
        $| = 1;

        ## There must be at least 3 arguments to this function.
        ##      1. First argument is the IP that has to be probed.
        ##      2. Second argument is the port to connect to.
        ##      3. Timeout

        if(scalar(@ARGV) < 3)
        {   
                return "Insufficient number of arguments, there should be three, something like:\n\nperl ajp.pl 192.168.1.1 8009 3\n";
    
        }   

        my $server_ip = $ARGV[0];
        my $port = $ARGV[1];
        my $timeout = $ARGV[2];
    
        my $errcode = 0;
    
        my $sendhex = pack 'C5' # Format template (pack the next 5 unsigned char (octet) values)
            , 0x12, 0x34        # Magic number for server->container packets.
            , 0x00, 0x01        # 2 byte int length of payload.
            , 0x0A              # Type of packet. 10 = CPing.
        ;   

        my $recvhex = 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.
        ;   
my $socket = new IO::Socket::INET (
        PeerHost => $server_ip,
        PeerPort => $port,
        Proto => 'tcp',
        Timeout => $timeout,
        ) or die "ERROR in Socket Creation : $!\n";

        $socket->send($sendhex);

        my $read;

        $socket->recv($read, 1024);

        ## Probe completed.
        $socket->shutdown(2);

        if ($recvhex eq $read) {
                # a successful probe should return a line like this:
                # success - AB
                # (from a test Jetty instance)
                return "success - $read";
        } else {
                return "Mismatch on Response - malformed PONG or other error";
        }

}

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Netscaler NITRO API 101: Logging in with Python

I’ll hopefully be an actual Citrix blogger soon, but in order to try this out, I thought I would post here first and see how it goes…..

If you are using one of the SDKs (Java or C#) then creating a NITRO session on the Netscaler is as simple as creating a new “nitro_service” object, choosing your connection method and setting your credentials appropriately. If have supplied valid credentials and your Netscaler is correctly configured then you can continue on your merry way and remain ignorant of what has just happened in the background. However, if you are looking to use another language to make use of the RESTful interface that NITRO provides, then you will need to know more.

The NITRO API Documentation is available from the Netscaler GUI, of course, but that serves as more of a functional specification than a guide to building a successful REST client in your language of choice. So, what exactly is required to take that first step and log in to a Netscaler?

The short answer is: A properly formatted POST request using appropriate credentials – easy, right?

Creating that properly formatted request, from scratch, can be more tricky that it appears. The exact requirements, along with an example, are after the break.

First of all, let’s take a look at some snippets from the API documentation (taken from Citrix NetScaler NITRO Getting Started Guide for REST API):

Request Payload:

object=
{
"login":
{
"username":"username",
"password":"secret"
}
}

That looks straight forward enough, but as always the devil is in the details. First of all, there are a few prerequisites omitted:

1. The request must include a Content Type header of: application/x-www-form-urlencoded
2. The “object=” string at the start of the payload is not just descriptive, it is required
3. The remainder of the payload should be URL encoded

Unless the above criteria are met you are likely to receive an error response (probably “Invalid Post Request”) as you attempt to login.

It is easy to list the requirements, but often times the code is far more useful. Here is a very basic login request example using the popular Python programming language:

#import the necessary libraries
import json
import httplib2
import urllib
#set the headers and the base URL
headers = {'Content-type': 'application/x-www-form-urlencoded'}
url = 'http://192.168.100.1/nitro/v1/config/'
#contruct the payload with URL encoding
payload = {"object":{"login":{"username":"user","password":"secret"}}}
payload_encoded = urllib.urlencode(payload)
#create a HTTP object, and use it to submit a POST request
http = httplib2.Http()
response, content = http.request(url, 'POST', body=payload_encoded, headers=headers)
#for debug purposes, print out the headers and the content of the response
print json.dumps(response, sort_keys=False, indent=4)
print json.dumps(content, sort_keys=False, indent=4)

The credentials and IP address of the Netscaler will need to be adjusted in the code above to suit your environment, but otherwise running the code above should be sufficient to log into a Netscaler and receive the required Session ID. What to do next with that Session ID will be the subject of the next post.

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I figured I would share some of the information gleaned from the experience, as it was less than well documented on the interwebs.  The transfer process is an interesting one and my first tip is to make sure that if you are moving to a new hosting provider at the same time (as I was) that you update the DNS for the domain first – you’ll see why when I describe the rest of the process.  Once you have that done the first step  involves unlocking the domain – this is one of those things that gets mentioned a lot in guides but no one explicitly tells you what it means – for those that don’t know, that looks something like this when you do a whois lookup:

Status: CLIENT-XFER-PROHIBITED

That is normally a good thing – prevents a transfer being kicked off without your knowledge by someone with nefarious intent.  Changing it is a less than transparent task though and involves getting into the registrars admin tools and finding the correct option to un-tick (assuming they expose it at all).  Once that is done you then have to initiate the transfer – the first stage of that is a confirmation request to the registered owner of the domain (hopefully an e-mail address you still have access to) by the registrar seeking the transfer, followed by another confirmation request to the same address by the registrar that currently holds the domain.  This all takes several days, so you have to be sure you get this done long before the domain is due to expire and that any housekeeping on the domain is done in advance.

In terms of the hosting transfer, my new provider (Dreamhost) allows the use of free sub-domains (of the form name.dreamhosters.com) so that you can set up your site on their systems and test it before taking the plunge and moving everything over.  They also have a Cpanel importer to help which partially worked and saved me some time – not perfect though.  Their Rails hosting support is far better and my Redmine instance is up and running now without issue.  So far, so good – let’s hope it continues

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Speaking of which, my Aol. days are now drawing to a close.  I have chosen to accept the voluntary package and move on from what is my first real job.  I started at AOL when I was 19 years old and it’s with a mixture of sadness, fear and excitement that I leave that company over 11 years later having made great friends in several countries and learned an enormous amount.  Linked In can point you in the right direction regarding my qualification sif you are looking for someone with extensive experience in everything from dial up connectivity to web operations and Linux system administration.

Oh, and in reference to the post below, I caved and bought the iPhone.  However O2 left such a nasty taste in my mouth that I will likely switch providers as soon as I can out of principle, so I didn’t cave really, right?

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I’ve also found the interface on the Nokia N95 I am currently using (thanks to a loan from John) to be very counter intuitive, which is sad since I used to think Nokia had a real edge when it came to UI design.  Two guesses what John traded his N95 for…..

There is not a single phone I have found so far with WiFi, GPS, a decent sized screen and a UI that gets a decent review.  If anyone can recommend one, then please let me know.  Assuming my Macbook Pro comes back to me in working order sometime in the near future I may have to look into getting an iPhone and jail breaking it to work on any network.

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I had often wondered how the Ood came to be, something related to Hollywood Video perhaps?

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New Orleans

Paul & Maria Visit

Lake House

New York (with Susan and Jay)

While I was at it, I upgraded to WordPress 2.5 – not sure how I like the new interface yet, but we shall see, maybe tryingt o make a decision will get me to post a bit more often

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As well as being available to install to your local PC we use it via a web interface to run tests from multiple locations and browser versions without the need to install them all or have multiple machines.  In these dark times of layoffs and plunging stock prices it’s nice to see AOL doing some things not focused on the almighty dollar.  Long may it continue.

Technorati Tags: AOL, open source, pagetest, Internet Explorer, firebug

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I have a single desktop across all 4 – to switch between machines I just drag the mouse to that screen.  Copy and paste works between the machines, with no problems.  There is very occasional lag between the server (linux) and the clients (the 2 Macs) but nothing that would cause me to reconsider using it – the benefits are far too great.

For more on the geek front, I came across this story, “The case of the 500 mile e-mail” which made me laugh and shows exaclty the kind of random crap that can end up coming in when you are in my line of work, although I must admit that my problems have never been quite as interesting or had quite as novel an explanation

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