Multi-Tenancy Explained

This post is an aggregation of a lot of valuable resources that I found on the internet when I was trying to understand Multi-Tenancy. The pictures are attributed to their respective authors. Please look at the References at the bottom of the post.

What is Multi-Tenancy?

Multi-tenancy is the ability to run multiple customers on a single software instance installed on multiple servers to increase resource utilization by allowing load balancing among tenants, and to reduce operational complexity and cost in managing the software to deliver the service.

Multi-tenancy is not multi-instance architecture where separate software instances (or hardware systems) are set up for different client organizations.

A multi-tenant architecture, would expect a software application to virtually partition its data and configuration so that each client organization works with a customized virtual application instance.
Tenants on a multi-tenant system can operate as though they have an instance of the software entirely to themselves which is completely secure and insulated from any impact by other tenants.

Strategies of Multi-Tenancy

Three buckets of multi-tenancy strategies:

QuickTip: Patching up JBoss 4.0.3 sp1 with EJB3

JBoss provides built-in EJB3 support version 4.2x onwards. For rest of the versions you would need to download the specif JEMSInstaller and patch-in the EJB 3 support.

This is what the JBoss site has to say

Important Note: If you want EJB3 or Seam support with JBoss AS 4.0.3 SP1, 4.0.4 or 4.0.5, you MUST download and use the relevant version of JEMS Installer together with JDK5.0. JBoss AS 4.2.x versions include support for EJB3, by default.

The problem is that when you download the JEMS Installer  for 4.0.3 sp1 and follow the instructions to get the EJB3 support working, it does not work! Your .ear would be deployed but the relevant services to load the EJBs are not started and they are not registered in the JNDI tree.

To get the EJB3 patch onto 4.0.3 sp1 you need to do the following …

QuickTip: Ubuntu 8.04: Setting the File Path for Bluetooth Transfers

Press Alt and F2 and enter
gconf-editor

Then navigate to
/apps/gnome-obex-server

QuickTip: Resolving Bluetooth Issues With Ubuntu 8.04 LTS

Around a month back I upgraded from 7.10 to 8.04

Most of the stuff worked fine except that my Bluetooth service was broken. I could no longer transfer files from my Nokia 3230 phone to my laptop. The steps defined in my earlier post did not work either and I was always greeted with an “Unable to connect” error. It became terribly irritating after a while and then there had to be a way to get around that.

The way that I suggest is one of the possible many ways, if you find something else please let me know. Read on …

QuickTip: JUnit: The input type of the launch configuration does not exist

If you are getting the above error message in Eclipse IDE, while running your test case, just make sure that you have the test class as a part of the “eclipse source folder” definition.

Easiest way. Right click on the folder –> Build Path –>Use as source folder

Done.

Role of an Agile Architect in Chinese!

A few weeks back I was contacted by Bryan Zheng. Bryan is a part-time editor of Agile Community of InfoQ China and his full-time job is working as the senior editor of Programmer Magazine which is a publication of CSDN.net. CSDN is the world’s largest Chinese-speaking online IT community with 2.6 million registered members. Programmer Magazine is the only and most popular software development magazine in China.

Bryan wanted to translate a couple of my articles to Chinese for the IT community thriving in China. First translation was for the article “Role of an Agile Architect”.  The English version of the article has already been published on Agile Journal and is also present on this blog site. You can download the Chinese translation which has been published in the Programmer Magazine.

Thanks to Bryan for sending me the pdf.

Is wordpress.com reeling under excessive user load?

I have been using wordpress.com as my preferred blogging site for over an year now. I saw the traffic of blogs being posted increase over the past one year gradually but surely. Whenever I hit the site to enter my blog site, I see upwards of 0.1 million blogs posted everyday. Pretty impressive.

However, for the past few days, I am greeted with inordinate delays in logging into my account. If at all the login somehow works, the stylesheets take ages to load.

This is how the screens look like.