The so-called "computer revolution" and "information revolution"

Alan Kay, the recipient of 2003 Turing Award for his contributions to object-oriented programming languages and personal computing, points out that "the computer revolution" has not happened yet :

The printing press was invented in the middle of the 15th century, yet it took 100 years before a book was considered dangerous enough to be banned. 150 years before science was invented, almost 200 years before a new kind of political essay was invented…The commercial computer is now about 50 years old and is still imitating the paper culture… we could claim that the computer revolution hasn’t even started.

Although it may not be a revolution from the current aspect, the computer is changing our life to what we cannot even imagine. Among all the computer-related technology development, the emergence of Internet is most significant. The use of Email and World Wide Web (WWW, or Web) boosts the popularity of Internet, though they are not the original design goals of Internet. The web has changed so many aspects of human life such as mass media, business, entertainment, science, and politics. It even introduces new elements to languages and cultures.

It is Nick's and Joe's articles that remind me to post part of my recent writing here.

You can watch Alan Kay's keynote at OOPSLA 1997 titled "The Computer Revolution hasn't happend yet."

Testing, modeling, and simulation of large-scale service-oriented systems

When many enterprises transfer to web services, large-scale intra- and inter-organization service-oriented systems are emerging. Compared to software systems such as stand-alone desktop applications and multi-tier web applications, we almost have no experience about testing large-scale service-oriented systems. A new level of complexity arises from the scale, open, and dynamics of such distributed systems.

When a service-oriented application is deployed, we expect that most aspects of its behavior are by design. However, when these applications are integrated to form large-scale systems, we have no confidence about how the whole system will work based on the knowledge of each application that could be very limited if the integrations are inter-organization. Service-oriented systems are open: A new application following the service contracts can join in and leave the system anytime. The dynamics of these systems are not just reflected on their scales, but also the structures. An approach to elicit knowledge for designing and managing such systems is modeling and simulation.

Frank Cohen writes an excellent article on testing SOA . The purpose of testing is more focused on performance and scalability rather than functionality. Werner Vogels has two posts on scalability and performance that help to understand these terms in the context of distributed systems.

I'm a Mandarin!?

You're an intellectual, and you've worked hard to get where you are now. You're a strong believer in education, and you think many of the world's problems could be solved if people were more informed and more rational. You have no tolerance for sloppy or lazy thinking. It frustrates you when people who are ignorant or dishonest rise to positions of power. You believe that people can make a difference in the world, and you're determined to try.

Talent: 51%
Lifer: 33%
Mandarin: 59%

Take the Talent, Lifer, or Mandarin quiz.

The best text editor

Many programmers have experiences of using UltraEdit as the code editor, even if they have some complicated IDE available. However, UE is a shareware ... You may want to try something that you do not need to care about expiration, then PSPad is the best text editor for you. I would like to say that PSPad suplies all the features I need. You can find an interesting artical on various editors here.

Load-balance Jetty using mod_proxy

Here are two reference articles for this topic: one from Jetty and the other by PierFumagalli. Although they were developed before the release of Apache Httpd 2.2, most of the configuration can still be applied to the current version.

Using mod_proxy and mod_proxy_balancer to cluster and load-balance Tomcat application servers

I just updated the Apache HTTP server on my Window box from 2.0.54 to the current 2.2.0. Release 2.2.0 includes many new features, among which mod_proxy and its extension for load balancing, mod_proxy_balancer are most interesting to me as replacements for load balancing using mod_jk. Graham King has a good article about how to setup mod_jk/mod_jk2 for clustering Tomcat using Apache. Now he also changed to the new mod_proxy and mod_proxy_balancer, and say goodbye to mod_jk. To setup mod_proxy_balancer in 2.2.0 is quite straightforward and you can refer to mod_proxy_balancer document and Graham’s post.

To test the load balancing of Tomcat, I have to start several Tomcat instances on my Windows system. I found some hints about running Tomcat instances on the same system from the Web, but they did not help me so
much. The method I figured out is as follows:

1. Download the zip version of core release of Tomcat, and unzip it to a directory where will be the Home of one Tomcat instance, say c:\tomcat0. Read the RUNNING.txt in the directory. The “Advanced Configuration - Multiple Tomcat Instances” part will help you a lot during the further configurations.


2. Download the Tomcat Native library and put it in the \bin if you want to improve Tomcat’s performance.


3. In server.xml, change the ports for connections to avoid conflict with other applications including other tomcat instances. Add jvmRoute=”tomcat0” into the line of < Engine name="Catalina"
   defaultHost="localhost" > to specify the route required in < proxy/ > entry of httpd.conf.


4. At the beginning of startup.bat and shutdown.bat, set both CATALINA_HOME and CATALINA_BASE to be c:\tomcat0.


5. Copy the folder c:\tomcat0 to c:\tomcat1 to create another Home for an instance, and change its server.xml, startup.bat and shutdown.bat correspondingly.

Now you can run startup.bat in c:\tomcat0 to get the Tomcat instance of tomcat0, and the same for instance of tomcat1, and so on.

I have tried both ajp and http connections to forward the request from Apache proxy to Tomcat instances, and using JMeter to test the performance of both options. Unfortunately, ajp always triggers exceptions related to socket connections. My Tomcat log is quite similar to those catched when using mod_jk . I am not sure if that mean we cannot avoid the bugs in org.apache.jk package even if switching from mod_jk to mod_proxy_ajp. Therefore I suggest to use http to connect Tomcat with Apache other than ajp at this moment.

A nice FREE webcam software for Windows

I just installed a webcam software named Fwink. It is light and works perfectly.