Twitter: From Ruby on Rails to the JVM [video]

    > On the other hand, many people seem to come out and say that Ruby is _very_ slow. 
    > Is it heaven-and-earth slow?

Comparatively, I would say yes. Granted, most of the time it won't matter because you are waiting on IO (disk/network), but if you are doing cpu intensive work, it is slow and you probably need to drop down to C or offload that work to another service.

    > How is Erlang more scalable than Java? In what area? horizontal vs vertical scaling?
    > developer's productivity (or team performance) scale? performance? speed? Erlang seems 
    > to excel in a niche area (in a positive speaking).

My guess would be in single server scalability. Erlang's write-once variables and actor model, combined with a good VM ("green processes") make it very single-server-scalable (verticle). It also has good built in node-to-node communication mechanisms (horizontal). Performance is probably slower than Java though. And I imagine the developer pool is much more limited than that of Java.

    > What about Haskell/Ada, how are they safer than Java? 
    > Do they have better type-systems? handles NULL better than Java? 
    > Bulletproof from developers? detect more bugs?

I meant safer in the type-safety sense, yes. There are also classes of static analysis tools for both. Granted, my knowledge of these languages is quite limited.

I certainly see your points (especially about liking the code hygiene of python), and agree that Java is not going anywhere soon. I guess I don't understand why a startup, or individual developer, would choose Java over other languages, even other languages on the JVM, for new projects.

Thanks for the good discussion. :)

Java ecosystem has a lot of static analysis tools that can integrate to almost all popular IDEs and Continuous Integration systems. Findbugs, PMD, JDepend, Sonar (recommend to check Sonar).

Checkstyle is another tool that I use since I'm kind of the annoying dude when it comes to code-style. (Have you seen GWT API code? it's like written by one person as opposed to a few developers with different perceptions of "readable" code. I like that kind of thing).

There are a few reasons why startup/individual dev would choose Java:

1) Previous experience in Java

2) Java fits better for the type of problems to solve (intensive computational that requires Hadoop like infrastructure)

3) Emotionally attached to static/compiled language with nice IDE so that one can navigate the source code easily whether the code base is large or small (sometime not all decisions are rational and I'm okay with that because developing software requires more than technical skill; it also requires passion).

4) Marketing (if you're targeting the enterprises). Zimbra, Jive Software, Compiere, Alfresco, Day software, Liferay, Salesforce used to be startups.

Java ecosystem seems to learn and grow in a much better speed thanks to the following actors:

- Rails (Spring Roo, Spring MVC, JPA 2.0, and possibly MVC framework from the upcoming JEE releases)

- C# (Java 7 new features, Java 8 closures/lambda. Yes, Lisp does this first, but I think C# forces Java to implement closures more than any of its competitors).

- REST/JSON/WS (Check out the latest JAX-RS, supports REST, JSON, XML, Atom-Feed, and JAX-WS)

- I/P/SaaS + Cloud Computing (Targeted for Java EE7, deployment, infrastructure to support multi-tenant, etc).

NB: Just so that I don't sound like a Java fan-boy, I use Java by day but I use and help to promote and organize Python community overseas (of course by not comparing Python vs Java :)).

The point is you probably never need that performance gain on the VM level (YAGNI) at all. Things are changing very fast in software development, your project could die or fail long before you really think about performance optimization on the VM level. But when you start a project and think that my project will fail because I use Rails and Rails doesn’t scale, you are doing it all wrong! What you really need is a tool that helps you iterate faster. Rails falls into this category. And that’s the productivity gain that I am thinking when starting a company.

As a pragmatic approach, a half century of software engineering says that you should write the code first and worry about making it faster only if it is too slow. Donald Knuth is right: Premature optimization is the root of all evil. Don’t merely let the VM performance metric blind you to this fundamental truth. If you are chasing for a performing language, Java/Scala is not your ultimate solution, C/C++ is, even Erlang.

I actually don’t see a problem with “performance” emerging as the requirement in the Ruby world sooner than others, say Java/Scala, because this “sooner” is very contextual and depends a lot on the implementation. To give you more info, GitHub is on RoR since it started, and till now they haven’t hit the so-called “Rails does not scale” point ( http://teachmetocode.com/podca... ). So are many other projects. Besides, think about Twitter, they only recently try to port everything to the JVM, after Rails has served them a couple years. All these facts tell you, this “sooner” may never happen to your own app, and most importantly, Rails can scale, although it may not scale as well as others! But once you hit the point where Rails, or Ruby in general, doesn't meet your performance requirement (assuming you are lucky enough to build another Twitter), do what Twitter suggests you to do in the video. Is that too late? Not at all. Because by then, you have the resources to do whatever you want, even inventing a VM that is more performing than JVM.

To summarize, the Ruby VM was fast yesterday, is still fast today, and will be faster tomorrow. In 90% of the cases, it's just fast enough. Do I need the performance gain by switching to JVM? Don't know yet. It'd be better to let the market drive you. Does Rails provide the agility I want to start a project? 100% hell yeah!