Lean Programming

Lean Programming teaches you to eliminate wasted effort in development projects by favouring “pull” design over “push” design. This means infrastructure concerns should be only designed and built to satisfy the needs of business requirements (pulled on demand) instead of building that what you think the application will need later.

This means you should develop the system incrementally by developing vertically – by building one feature at a time instead of building the system one horizontal layer at a time. By working this way you can be sure that infrastructure development is no more that what you absolutely need.

Working horizontally you risk following:

• Not getting adequate response of what you are building (no functionality to demonstrate)
  
• Writing unnecessary code for a features that will not be in a built
  
• Building wrong code because you don’t understand business requirements, or requirements has been changed

IPod touch wireless network password is case sensitive

I have spent a few hours trying to connect iPod touch to my existing wireless network without success. My wireless network is WPA with password, and finally got it working. The problem was with the password itself. It consists of capital letters and numbers. By default iPod enters letters as lower case, and it did not work. It was inconvenient to press shift all the time, and my thought was that password anyway is hex string so it should not be a problem. But it was.

Technology we use in development

Technology we use, are rapidly changing. Take a look at http://gantter.com, this site has been created by one person. One person? When I have a first look at site I had an impression that this work was done by a big company aka Google or similar size company. That is a really an estimate for amount of work. Could the technology give a developer ability to achieve more and spend less time for development? Probably that is the case. As an outcome of this shell be next – we must constantly follow new trends and techniques to be more productive. Our time is precious thing and we should not spend it unwisely. 

Install Subversion server 1.5 on Windows 2003

I have look over Internet for how to install Subversion server and found that in general this information is related to the Subversion server prior to version 1.5 that have been just recently released by CollabNet.

Now installation could done in just a few steps:

1. Run CollabNetSubversion-server-1.5.0-22-win32.exe
3. I have running IIS on port 80 so I have selected svnserve checkbox only and uncheck apache server checkbox
3. Use default settings on following steps
4. After install is completed start subversion service from Administrative Tools-> services
5. Run next command from command prompt, to create repository (similar to VSS database). It is a good practice to have repository per project:

svnadmin create "C:\svn_repository\yourprojectname"

6. Create users and passwords by modifying svnserve.conf and passwd files in C:\svn_repository\yourprojectname\conf subfolder
There are should no spaces in front of user name, otherwise you will recieve an option error.
7. Open TCP port 3690 in a firewall

To configure client computer:

8. Install TortoiseSVN-1.5.0.13316-win32-svn-1.5.0.msi on client computer
9. Connect your project folder to svn repository by right click and setting url to you repository. It will prompt you with user and password dialog box.

Schedule weekly job with cron and PHP

Several approaches might work depending on hosting configuration. The most straightforward approach with panel is to find cron jobs icon and select standard or advance version. Both of them have same information - standard form has combo boxes vs entering number into textbox in advance form. That should be done for specifying date and time when job should be executed. First version of command line used for setting a job is:

php /path/to/script.php

Possible error is "No input file specified."

php /home/<myhomedir>/public_html/admin/job.php

Possible error is "No input file specified."

/usr/local/bin/php /home/<myhomedir>/public_html/admin/job.php

Possible error is "Could not open input file: /home/<myhomedir>/public_html/admin/job.php."

/usr/local/bin/php $HOME/public_html/admin/job.php

Last version of command line should work.

Lock free communication channel

By taking advantage of existing Windows XP API such as InterlockedPushEntrySList and InterlockedPopEntrySList is possible to decouple data exchange in communication channel. That is very important in places where processing speed is crucial point. “An interlocked singly linked list eases the task of insertion and deletion from a linked list. Singly Linked Lists are implemented using a non-blocking algorithm to provide atomic synchronization, increase system performance, and avoid problems such as priority inversion and lock convoys.” Access to the Singly Linked Lists is synchronized on a multiprocessor system, and with no need of locking mechanism.

Writer’s thread will save data into Singly Linked Lists and assign unique ID to the package. Then reader’s thread will pick packages one by one, order them by ID, and store packages in a cache list.

The cache itself could be ignored when processing is interested only in latest package – real time data. Since InterlockedPopEntrySList could read packages in random order, is considered necessary after extracting all packages from a cache to find latest one.

Singly Linked Lists are straightforward to implement and use in 32-bit code.

SQL Express failed to install

During SQL Server Express installation on Microsoft Windows XP Home Edition next unexpected error occurs:

Product: Microsoft SQL Server Native Client -- Error 1706. An installation package for the product Microsoft SQL Server Native Client cannot be found. Try the installation again using a valid copy of the installation package 'sqlncli.msi'.

Workaround:
Extract 'sqlncli.msi' file from a package and install separately, then run SQLEXPR32 again.