Saturday 11 December 2010

YOW 2010 - loose thoughts

It doesn’t happen often that nearly every single talk at a conference is great and on top of that half of them are actually funny. That’s YOW 2010 for you summarized in one sentence :).

Justin Sheehy explained how to quickly narrow down the choice of database technologies that might be useful in a particular case. His method is based on a simple matrix of operations requirement (local, single server, distributed, etc) by data model (relational, column families, key/value, etc). Once this is done and there are only a few solutions on the table a more sophisticated and time consuming research can be conducted to choose the right solution. Every single NoSQL solution is different and a generic split SQL/NoSQL doesn’t really make sense. It’s all about tread-offs. It’s amazing how often this simple fact needs to be reminded.

Eric Evans talk was focused on the idea of bounded contexts. In other words a single enterprise model is an anti-pattern and is one of software engineering fallacies. Eric mentioned also a few disadvantages of doing big design upfront (AKA let’s build a great framework that less skilled devs can use) and postponing the initial release for long time. Nothing really new but it was well delivered.

Gregor Hohpe talked about trade-off decisions that Google had to make to be able to reach its current scale. He covered the whole spectrum of optimizations from data access at the disk level to minimize heat generation to skipping some longer than expected running parts of map reduce executions to make sure results are delivered in timely manner. When I asked Gregor if Google uses regular Pub/Sub or transactions he said that if there is a technology out there Google has built something on top it :). Just use the right tool for the job.

Second day started with Erik Meijer explaining coSQL (AKA NoSQL). It was a funny presentation about what NoSQL really is and how it relates to SQL. They both complement each other even in a mathematical sense hence the co part of coSQL. Additionally co is more positive than no and this makes Erik happy :).

Jim Webber talked passionately about how much he hates dislikes ESBs and how rarely ESB is the right tool for the job. His presentation was extremely funny but still full of useful information. The main point was that a custom built system can be cheaper (but not cheap) and less risky to deploy than an out of the box ESB which often requires a substantial up-front cost.

Dave Farley took us to the world of <1ms latency and speed of 100k per second. According to Dave this is achievable on commodity servers. The main enabler seems to be lack of synchronization, keeping as few threads per core as possible, keeping all the data in memory and keeping methods very short. 1 CPU can execute 1 billion instructions a second. That’s a lot and as long as we don’t waste it today hardware should be more than enough for needs of most consumers. The main message was that we underestimate what we can get from today hardware. I suppose this is only partially true because nowadays we rarely deploy apps on real hardware. In most cases all we see is a VM that shares the host with Gazillion of other VMs. This might the main reason why the perception of the current hardware capabilities is skewed.

After the conference there were 2 days of workshops. I spent the first day with Ian Robinson and Jim Webber learning about REST. What I believed constituted a fully blown RESTfull service was actually a very basic RESTfull service that scores only 1 out of 3 points in Richardson maturity model. Each of the levels has its place but obviously the higher you get the more you take advantage of the Web and that’s the whole purpose of using REST. REST is CRUDish as it mostly relies on GET, POST, PUT and DELETE. My initial thought was that this is very limiting but then it turned out that it doesn’t have to be. The same applies to lack of transactions. This can be worked around with proper structure of resources, meaningful response codes and proper use of HTTP idioms. Another important thing to keep in mind is that domain model shouldn’t be exposed directly. What you want to expose instead are resources that represent client – server interactions (use cases). In most cases O(resources) > O(domain classes) – notation by Jim Webber :). The Web is inherently based on polling (request/response) thus REST is not suitable for apps which require low latency. In this case you might want to use Pub/Sub.

The next day I attended a workshop with Corey Haines. This was a true hands-on workshop. I spent at least half a day writing code retreats, code katas and coding dojos. Going back to the very basics was surprisingly refreshing. I spent two 45 minutes long sessions constantly refactoring maybe 15 lines of code until most of if statements were gone and code read properly. You wouldn’t do this at work but the whole point of the exercise was to actually go over the line and try to come up with best possible code without feeling the time pressure.

At last but not least, the attendees were fantastic and every coffee/lunch break was full of valuable conversations.

I had an amazing time and YOW 2010 is the best conference I’ve ever been to.