Friday, August 17, 2012

5' on IT-Architecture: the modern software architect

Before I start writing about this let me adjust something right at the beginning:
Yes of course, there is the role of a "software architect" in any non-trivial software development project. Even in times of agile projects, dynamic markets and vague terms like "emergence". The simple reason for that is that emergence and democracy in teams only work within constraints. Though, it's not always clever to assign somebody the role explicitly. In an ideal world one developer in that team evolves into the architecture role.
When I started working as an IT professional at a *big* american software & IT consulting company I spent around five years with programming. After that time I got my first architecture job on a big project at a german automotive manufacturer. My main responsibility was to design the solution, advice developers, project managers and clients in doing things and to organize the development process. I wrote many documents, but I didn't code anymore. The result was that I lost expertise in my core business: programming. So after a while my assessments and gut instinct got worse, which results in worse decisions. As a sideeffect of generic (vague) talking it got harder to gain acceptance by the developers, project managers or clients. When I realized all that I decided to do more development again. Today, I am doing architecture for 10 years. I am developing code in the IDE of my choice at least 20-30% of my time.

Wednesday, July 18, 2012

5' on IT-Architecture: root concepts explained by the pioneers of software architecture

The last couple of weeks I am working on a new software architecture course specifically for the insurance and financial sector. During the preparations I was reading many of the most cited articles on software architecture. The concepts described in these articles are so fundamental (and still up-to-date) that every architect really should know about them. I have enjoyed reading such "old" stuff. I first read most of the cited articles during my studies at university in the mid 90s. It is surprising to realize that, the longer you're in this business, the more you agree to the ideas explained - in articles that were written 40 years ago! I've decided to qoute the original text passages - may be I thought it would be overbearing to explain it in my own words ;-) I hope you enjoy reading these text passages from the pioneers of software architecture.

Monday, June 25, 2012

5' on IT-Architecture: four laws of robust software systems

Murphy's Law ("If anything can go wrong, it will") was born at Edwards Air Force Base in 1949 at North Base. It was named after Capt. Edward A. Murphy, an engineer working on Air Force Project MX981, (a project) designed to see how much sudden deceleration a person can stand in a crash. One day, after finding that a transducer was wired wrong, he cursed the technician responsible and said, "If there is any way to do it wrong, he'll find it."

Tuesday, May 15, 2012

5' on IT-Architecture: three laws of good software architecture

The issue with architectural decisions is that they effect the whole system and/or you often need to make them early in the development process. It means a lot effort if you change that decision a couple of months later. From an economic standpoint architectural decisions are often irrevocable. Good architecture is one that allows an architect to make late decisions without superior effect on efforts and costs. Let's put that on record.

Friday, May 4, 2012

Java 7: NIO.2 I/O operations on asynchronous channels are not atomic

This part of my NIO.2 series wasn't on schedule when I started writing about NIO.2 aasynchronous file channels. It deals with an important detail: read and write operations are not atomic. What that means is that AsynchronousFileChannel -> write() does not garantee to write all bytes passed as parameter to the destination file. Instead it returns the number of bytes written as return parameters of the corresponding I/O operations and the client needs to deal with situations where the bytes written isn't equal to the remaining bytes in the passed ByteBuffer.

Java 7: Closing NIO.2 file channels without loosing data

Closing an asynchronous file channel can be very difficult. If you submitted I/O tasks to the asynchronous channel you want to be sure that the tasks are executed properly. This can actually be a tricky requirement on asynchronous channels for several reasons. The default channel group uses deamon threads as worker threads, which isn't a good choice, cause these threads just abandon if the JVM exits. If you use a custom thread pool executor with non-deamon threads (see last part of this series) you need to manage the lifecycle of your thread pool yourself. If you don't the threads just stay alive when the main thread exits. Hence, the JVM actually does not exit at all, what you can do is kill the JVM.

Thursday, April 19, 2012

Threading stories: ThreadLocal in web applications

This week I spend reasonable time to eliminate all our ThreadLocal variables in our web applications. The reason was that they created classloader leaks and we coudn't undeploy our applications properly anymore. Classloader leaks happen when a GC root keeps referencing an application object after the application was undeployed. If an application object is still referenced after undeploy, then the whole class loader can't be garbage collected cause the considered object references your applications class file which in turn references the classloader. This will cause an OutOfMemoryError after you've undeployed and redeployed a couple of times.