Kai Kreuzer

Choosing a Versioning Control System

Posted on March 9, 2010

When initiating an Open Source project like openHAB, one of the many questions you have to answer before you start is: What VCS should I use?

In the beginning I did not really realize that this is an important question. Being a professional Java developer building commercial products with Eclipse, the use of Subversion with Subversive as an IDE integration just seemed natural to me and not worth any further considerations.

It was more by chance that I noticed questions about using git on other OS projects that were using SVN as well as the activities in the Eclipse community around (E)git. When Ekkehard Gentz started a blog series about DVCS and Eclipse, I eventually decided that I needed to have a closer look.

After having grasped the great advantages of a DVCS, especially for Open Source projects, I then had to decide for one - to keep things simply, I only looked at the most popular ones, Git and Mercurial.

As I am using OSGi and Eclipse, there were quite some strong arguments for Git:

With JGit there is a pure Java implementation available
EGit is now under the Eclipse umbrella and actively developed by many gifted Eclipse committers.
It seems that Git is more hyped than Mercurial (at least that's my personal impression).
Git seems to be more powerful and flexible

Hence I installed Git and EGit and gave it a try. After working with it a bit, I noticed that I didn't really feel comfortable with it. It is difficult to say why, but I made out the following reasons:

I am a Mac and Windows user and Git somehow made me feel that its home is Linux. Although there is now a Windows version with msysgit, cygwin used to be the official way of using Git on Windows.
Coming from SVN, the Git vocabulary can be confusing - e.g. something like a svn revert is not done with git-revert, but with git-reset. Together with the abundance of commands and functionality of Git, this can easily make people feel lost if it's their first time with a distributed VCS.
The standard way for pushing and polling with Git is ssh - but this makes things much more difficult to use, if you are behind a firewall.
EGit is still an incubation project and there's still some way to go until it reaches a level like Subversive: There is no support for the "Team Synchronization" view, which I use a lot. It also had some trouble with deletion and renaming of files. Last but not least - it is lacking icons on the context menus. Ha, I know, this is only cosmetics and should not be relevant at all; but still it leaves the impression of being a version to early to be used.

Almost all of the above items felt better on Mercurial (and HgEclipse), so I finally decided to go for it. I guess on the long run, I might reconsider this, once EGit has matured, but for the time being I am happy with this situation. And it is very reassuring that there are plenty of tools around to convert a Mercurial repo into a Git repo and vice versa - so no decision needs to be taken for eternity!

Now I am only waiting for Ekke to finish his series to eventually see to what conclusion he came and which DVCS is the one of his choice :-)

Positioning openHAB

Posted on February 23, 2010

As already mentioned before, I have started the openHAB project not because nothing on the market could have provided me the desired functionality, but because I want to build something robust, stable and open with a modern technology stack.

If I were a pure user, I would still stick with Misterhouse as this has matured over the years so much that they are discussing on their mailing list already whether it's better to have a deer head or a magic mirror talking to you.

Well, I am not, and so I take the challenge to build something equally useful on top of a JVM. After Claude's comment I very much considered contributing to the openRemote project, tried to dive into the details of their code base and involved myself in technical discussion on their forum. But at the end, I decided against it, because all the main things that I would like to see covered are still on their todo list. That wouldn't be bad at all as it could have given me a good opportunity to contribute the missing things, but unfortunately - at least that is my impression - it would mean more or less a complete rewrite of openRemote...
Just to give you a few examples of what openRemote IMHO lacks:

No rule engine support yet
it has a "one-way" protocol, i.e. the client (e.g. iPhone App) is stateless -> it cannot show if lights are on or off, it cannot display values (e.g. temperatures), etc. Version 2.0 will bring a server push, but I am not sure when the client will support this?
No states are cached on the server which is definitely a problem for rules and stateful clients
No modularization / extension concept yet, it's one brick (the BOSS)
No easy protocol to implement for new extensions, see discussion about arduino support
No simple way to build from latest sources, so people are desperately waiting for an official build

I don't say that any of this is bad, I just want to highlight that their architectural approach obviously followed other priorities. I can imagine that openRemote and openHAB can cross-fertilize each other and maybe there is someday a possibility to integrate or even merge these projects - time will tell :-)

openHAB is out!

Posted on February 21, 2010

It took quite some preparation, but finally I can anounce that I have created the envisioned Open Source project for my (and others!) home automation needs!

In order to avoid any brandmark violations, I have reconsidered the name of the project, so that it is now called the open Home Automation Bus (openHAB).

You will find the project hosted at Google Code at http://openhab.org, even an initial codebase is already available. Although it's not doing much at all yet, it should give interested persons an idea of its architecture and show that things are moving and the project is on its way.

I will soon post further background information about the decisions taken, so stay tuned :-)

Reinventing the Wheel

Posted on November 21, 2009

As announced, I would like to tell you some details about my latest private project: SmartKNX!

I have spent quite some time in the past months with the Open Source project MisterHouse - a software for home automation. Initially, I have started using it, then I also engaged myself in the community and contributed some new features and bug fixes. Misterhouse really offers a lot functionality and it has quite a low learning curve for newbies. Especially, the iPhone interface is attractive, which has been mainly done by members of the german KNX community.

Accumulated Distraction...

Posted on November 20, 2009

It's a long long time since my last post, but I swear that I haven't been lazy or without impulses. Usually, I like to blog while being at conferences and it is not long ago that I attended the last one: The Eclipse Summit Europe 2009. As usual, it was a great event with many interesting people and lively discussions.

But a few things detered me from directly blogging about my impressions this time. For example, the ESE2009 organizers did not provide any public Wifi access to the attendees this time. I am not sure whether this was because the Wifi used to be heavily overloaded in the past years or if they just wanted to draw attention to the talks; if latter, this might indeed have worked out as I have seen much fewer people typing on their Macs throughout all sessions... Another reason for not blogging at this occasion was that I was invited to an X-Box soccer competition by the Itemis guys until late at night; these chaps seem to always be prepared for everything ;-) Last but not least, I didn't find much time to blog on the last conference day as I was called to hospital for the birth of my second son - well, I hope that at least this can be accepted as an excuse.

Despite all these distractions, I have been working quite eagerly on a new private project that I will very soon blog about; it is quite fascinating and if all goes well, I might present it on a future ESE - let's touch wood!

One last remark: As I missed a few sessions at ESE due to my early departure, I am taking the opportunity to join the Eclipse Demo Camp in Frankfurt next Thursday. There are already more than 60 people registered for it, which is quite astonishing. So if you are around and don't have any other plans - join me there!