Jabber-Server-Farming-HOWTO.pdf
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Jabber Server Farming How-To
Jabber Server Farming How−To
Ryan Eatmon
Jabber.org
reatmon@jabber.org
2002−06−06
Revision History
Revision 0.1
2002−06−06
Revised by: rwe
First draft.
Provide Jabber admins a look into the present and future of Jabber Server Farming.
Jabber Server Farming How−To
Table of Contents
Chapter 1. About this How−To.
.........................................................................................................................1
1.1. Purpose / Scope.
................................................................................................................................1
1.2. About Jabber.
....................................................................................................................................1
1.3. Feedback.
..........................................................................................................................................1
1.4. Copyrights and Trademarks.
.............................................................................................................1
1.5. Acknowledgments and Thanks.
........................................................................................................1
Chapter 2. Introduction to Jabberd and Farming.
..........................................................................................2
2.1. Jabberd − The Jabber.org Jabber Server.
..........................................................................................2
2.2. Farming.
............................................................................................................................................2
Chapter 3. Implementing the Farm
..................................................................................................................3
3.1. Client−to−Server Farming w/ Round Robin DNS.
...........................................................................3
3.1.1. The Dream.
..............................................................................................................................3
3.1.2. The Reality.
.............................................................................................................................3
3.2. Connection Redirection.
...................................................................................................................5
3.2.1. The Dream.
..............................................................................................................................5
3.3. Router Layer.
....................................................................................................................................6
3.3.1. The Dream.
..............................................................................................................................6
3.4. Moving JSM State data into a DB.
...................................................................................................6
3.4.1. The Dream.
..............................................................................................................................6
3.5. Multiple JSMs.
..................................................................................................................................6
3.5.1. The Dream.
..............................................................................................................................6
3.6. JSM Communications.
......................................................................................................................6
3.6.1. The Dream.
..............................................................................................................................6
i
Chapter 1. About this How−To
1.1. Purpose / Scope
This document was started on June 06, 2002 by Ryan Eatmon to explain how to set up a Jabber Server Farm
using the Jabber.org Jabber Server (
http://jabberd.jabberstudio.org
).
This document is broken into two main sections. What is, and what will be. As of the writing of this document
the Jabber Server does not have all of the pieces that are required to do full farming. There are steps that can
be taken to get partial farming, and those will be covered. There are also steps that we are going to take, and
those are covered to so that others can contribute and comment.
1.2. About Jabber
Jabber is an Open Source Instant Messaging System that uses XML as its base protcol. I could spend an entire
How−To describing Jabber, so I am just going to point you to the Jabber.org web site.
(
http://www.jabber.org
)
.
1.3. Feedback
Comments on this How−To may be directed to the author (
<
reatmon@jabber.org
>
).
1.4. Copyrights and Trademarks
Copyright 2002 Ryan Eatmon
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free
Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front−Cover Texts, and with no Back−Cover Texts. A copy of the license is
included in the appendix entitled "GNU Free Documentation License".
Jabber is a Trademark of Jabber, Inc.
1.5. Acknowledgments and Thanks
Thanks to everyone who gave me hints and tips on tuning Linux and structuring of the farm. This includes
Thomas Muldowney, Jeremie Miller, and other members of the
<
jabberd@jabberstudio.org
>
list.
Chapter 1. About this How−To
1
Chapter 2. Introduction to Jabberd and Farming
2.1. Jabberd − The Jabber.org Jabber Server
The Jabberd server is a reference implementation for the Jabber protocol as defined by the Jabber Software
Foundation. It is written in C and is covered by both the Jabber Open Source License(JOSL) and the GNU
Public License(GPL). The Jabberd project has its own documentation.
(
http://jabberd.jabberstudio.org/howto.html
)
.
2.2. Farming
This is an interesting topic. When you think of a server you tend to think of a single machine running a single
program. Farming is the idea of multiple machines running multiple programs that all act together to appear to
be one machine/program.
Why farming? Two reasons with equal importance. Scalability and Reliability.
Scalability is the idea of allowing something to handle many many more connections/transactions at the same
time. A typcial web server can handle say 1000 connections a second, but 10 web servers acting together can
provide 10,000 connections per second.
Reliability is the idea that even if a piece of the system goes down, the system does not. There is no single
point of failure, and there is built in redundancy to ensure that something is there to pick up the slack if
something goes down. In the web server example, if one web server goes down you could not send any
connections to it until it is back up, thus ensuring that your web site is always up.
Both of these ideas are crucial to a successful Farming strategy. Each wants to push the design into a different
direction, but they can be reconciled into a single design that can scale and is reliable at the same time.
Chapter 2. Introduction to Jabberd and Farming
2
Chapter 3. Implementing the Farm
3.1. Client−to−Server Farming w/ Round Robin DNS
3.1.1. The Dream
The first thing that we can do is to split out the c2s from the server and make it a seperate process/component.
Once that is done, we can replicate the c2s processes over multiple machines. Each one would connect back to
the main server running the JSM and everything should work just fine.
Figure 3−1. c2s Farming Diagram
Pros:
·
Easy to setup right now.
Cons:
·
Round Robin will not provide true load balancing since there is no mechanism in place to check how
many connections a server has when it forwards a new connection to it the next time it comes up in
the Round Robin.
3.1.2. The Reality
This is doable right now. The 1.5 version of jabberd has sought to break all of the pieces out into seperate
processes. This was not done for farming specifically, but we will not complain since the jadc2s component
can handle upwards of 10k users. (The 1.4.x series c2s could only handle ~1024).
Currently there is a forked version of jadc2s that works with the 1.4.2 server. It is located in the jabberd14
CVS repository on JabberStudio. The following example is running with two jadc2s boxes, and one central
Chapter 3. Implementing the Farm
3
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