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.

Solution for listServices.jsp of Axis 2 returning errors

The errors indicate that "root cause java.lang.NoClassDefFoundError: org.apache.ws.security.handler.WSHandler". The problem is caused by XPath lib. Download and install the xalan-j lib of 2.6.0, and that will be fixed. You can find detailed information at jira.

Stateless process manageability

It is a common principle of SOA that services are stateless. The statelessness supports loose coupling, reusability, and composability of services. In the principled Web architecture, stateless communication improves the system's visibility, reliability, and scalability. When the applications of cookies and other approaches in the Web make the communication stateful, the visibility and reliability of Web applications are degraded. Similar to the case of Web architecture, services can be developed to manage state information, but that would detract from some benefits of SOA. However, it does not introduce any conflicts in managing stateful processes and process instances using stateless web services. That directly implies that the process state information is carried by the messages or events going in/out the manageability services, and some applications maintaining the state information are hidden behind the manageability services.



Manageability services communicate with the applications maintaining state information through specific application protocol. On the other side, the communication between manageability consumers and manageability services just need to follow the open service protocol. Databases can store large amounts of state information of processes and process instances during and after their lifetime. Another kind of application, like message topics, maintains a certain group of messages with state information. The management of BPEL processes is essentially monitoring, tracing, and controlling the states through the corresponding manageability service endpoints.

Tools to manage the documents

Reading and referring papers and books are two everyday activities for the investigators. There are many commercialized tools to manage the documents. I recommend 3 pieces of software for free in this note.

JabRef is an open source project for BibTex database management. It is developed using Java, and has a neat GUI. If you are familiar with Latex and BibTex, it is very easy to handle the software. It also supports to import data from most reference sources. For Word users, it can generate RTF according to the output template included in the release package or defined by your own.

For those who have thousands of documents saved on local disks, it is unlikely to input the entries for each document to a database. It is better to have a tool automatically index the documents for us. The current version of Google Desktop Search can index and search documents of Word, Excel, PDF, PowerPoint, and even the caches of most popular web browsers. The search results are organized the same as the Google web search.

Docco is a part of the open source project named Tockit. It can index the text, html, xml, pdf, and word documents in a folder, and generate a graph with nodes as the searching keywords. The user will see the frequencies of each keyword and their combinations in the document collection. The process of indexing could be very long if the indexing folder contains lots of document. However, never set the indexing priority to the highest because the system will appear non-responsive.