Reaktor Dev Day – my first impressions

First ever Reaktor Dev Day is over and organizers can be proud of themselves. I’d be understating if I would say they did a good job and exaggerating if I would say that it was an amazing experience. Whatever the scale is, it is clear that Dev Day did set the new bar to technical conferences and events in Helsinki.

Dev Day was an amazingly refreshing attempt to bring the dev back to developer conferences. Idea of hands on sessions is great, but I heard from multiple participants that the timeslot ended up to be too short to gain proper experiences and that there was propably a too little Eclipse shown on the screens compared to showing powerpoints. But then again there were really happy people coming from – for example – Introduction to Scala session – so for some subjects, sessions and participants those sessions were right what they wanted.

Personally I did not participate in the hands on sessions as I was busy meeting with people at the conference – and watching two great presentations – one from Otto Hilska ( Flowdock ) and one from Reaktor’s Lasse Koskela. I had really wanted to participate in Introduction to Scala session – especially as it was being held by Markus Hjort and Sebastian Nykopp, two smart and funny guys who apparently did also a good job in the session – at least based on the discussions while going to the after party. Looking forward if they would hold the same session for Agile Finland community as a coding dojo or in some other event.

Challenge in any technical conference and session is always the level of presentation and balance of high level concepts versus technical details and actually showing something running on your machine or in a server farm somewhere. As Dev Day was visioned to be something from developers to developers there was a good effort done in making sure that sessions had real value for participants. Below is my take on sessions I participated and what I heard as second hand experience from others.

Scaling up and out with Scala and Akka

Odersky and Bonér made some compelling points and I am tempted to someday try Scala more seriously. Akka framework had interesting ideas and as they take concepts from Erlang, there is a solid foundation to build on too. I still have my own reservations and challenges, but I am trying to do my best to learn and adapt — to think more in functional way also in Java and think about how the code I write could be expressed later on also in more functional terms.

Not going to be Scala zealot in any time soon.

Real-time web architectures

I only had the time to see last few minutes of Otto’s presentation, but heard good commentary and discussion about real world experiences both in good and in bad. After the session I had the pleasure to talk with other people about the session and their take on the session, which was really good. It is always nice to see and hear modest presentation from guys who know what they are doing – and can also say when something does not work, instead of just continuing the hype and forcing also others to drink the koolaid.

Not going to be Rails guy anytime soon, but will continue to use Flowdock and keep an eye on the company.

Cross-platform mobile development with JavaScript

Lasse Koskela provided us with an overview of status of mobile development with JS and PhoneGap, but unfortunately for me did not provide that much new insights – rather than more confirmation to my own experiences and analysis on the situation. As Lasse is way more experienced in actually doing stuff with those frameworks, this kind of confirmation from him is in it self really valuable – and for anyone who has not done his own experiments or research, Lasse’s presentation proved to be a really good introduction into the subject. I would have liked to hear more analysis and insights into the differences and opportunities with different frameworks, but even as it was – this presentation was rather good and really valuable.

Bonus points to Lasse for his really good presentation skills and ability to also make the audience laugh. It is always nice to participate in a session, where the presenter knows his stuff and can also present those ideas in clear and concise manner. As a future idea it would be nice to have a similar session with workshop experience, where we would build something to test in our own phones with PhoneGap.


I did not see the start of the session, but based on the parts that I see – I have to say that this session was more or less golden. Tuomas Kärkkäinen presented the subject really well and included enough code examples in his presentation to make the ideas discussed clear.

Even though I could say that I am familiar with XSS in the backend, this session proved to be valuable in the sense that it reminded us all that as more and more stuff goes to be run in the client as javascript code, there are numerous new opportunities to fail spectacularly — especially if those guys writing the javascript do not have security minded focus and experience with different attack vectors available to bad guys.

If you did not see his presentation, I suggest that you head over to DOM XSS wiki and start to read about the subject as there are good possibilities that you have not even thought of these potential vulnerabilities.

Distributed ”Web-scale” systems, the Spotify way

Unfortunately this was one of the sessions where I was once again most of the time somewhere else. As I have had some experience and been reading a lot about high availability and scalability solutions, presentation seemed more or less repetition of those ideas and principles. However there were few small gems in the presentation also for me.

And yes, I am listening to Spotify also while writing this post.

API design done right

I had really great expectations for this presentation and more or less the session was what was expected. However I had a quite similar experience as with Lasse Koskela’s presentation – namely that the presentation was reassurance and confirmation for things that I already knew and used. That is not to say that Ville Peurala and Jari Mäkelä would have done a bad job, but actually quite the opposite. They ran through a good list of examples and clearly showed what problems and possibilities different design choices had.

It could be that many others felt the same as the presentation was over quite fast – and I still had good time to see the end of Scott Chacon’s presentation about Git.

A Tale of Three Trees

I am a mercurial user, so excuse me for not being too exited about this initially.. Especially as I am also a sucky mercurial user, meaning I use it mostly almost like subversion, committing often to the local repo and then from time to time pushing to the Bitbucket to collaborate with friends.

As my personal workflow has been so simple, I haven’t seen that much value in playing with Git — but to be fair to Scott, I have to say that now I am tempted. What I got from his talk was the part about Git reset ( see also ) and what it will actually mean for your workflow, especially if you collaborate in a larger project and do not want to pollute the history tree with multiple bad work item commits.

The big idea I got was that with reset in git you can collapse the history tree and push out only stuff that matters, even though you would have had a gazillion work commits in the middle. Then what your friends see in the repo are actually just the meaningful commits and they admire your skills… as you just managed to write a whole new kernel driver in just two commits.

This should also be possible in Mercurial, but haven’t yet looked at how to do it as I have not yet needed it. My friends already know that I make stupid mistakes and I am not ashamed to show them.

The Business of Open Source

This was most content free yet inspirational presentation of the day. Scott Chacon is an amazing presenter and had the audience listening and laughing the whole time. Main point were that people can learn from open source, open source is good and we can also create better work environments, where developers can and like to work most efficiently. Oh yeah, and use GitHub.

I enjoyed the presentation as well as looking how people in the audience reacted to it.

Before the last presentation beer and cider was already being served, so it was clear that serious part of the conference was already over.

I’ll write more about the day later, especially from the viewpoint on what we all can learn from the event — and what we all could as a community to do more together in our agile dinners, Scan Agile and other events. Like I said, Dev Day was really refreshing – and even though Agile Finland’s community based events are run with +-0 budgets, we can still learn something from the Dev Day and work together to create other great events!

Congratulations to all the organizers for the great job! You guys did a heck of a job.

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Yksi vastaus artikkeliin: Reaktor Dev Day – my first impressions

  1. Timo Rantalaiho sanoo:

    Cheers Heimo, thanks for the kind and thorough report!

    About rewriting the commit history with Git: Being more of a novice user, I myself find interactive rebase

    git rebase -i

    A much easier way for cleaning up commits. Typically before push / svn dcommit I revise the last commits with log and/or log -p, and if I want to clean up something, I do something like git rebase -i HEAD~n where n is a number of commits sufficiently big to show some context for the stuff I want to rewrite.

    Somehow it seemed that using git reset for that would be something that a power user like Scott could be comfortable with🙂 But maybe I should think about it wit a broader mind and try it…


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