Over the last week or two there’s been a bit of commotion with various parties in the blogosphere making the case for Scala against Erlang or for Erlang against Scala. Here’s a see spot run summary of the main writers and their positions / content:
Ted Neward (1, 2) – Ted (how confusing) is in the Scala camp, and thinks that the library approach of Scala’s actor library is preferable to Erlang’s VM (BEAM). He cites managability as a major concern. He also thinks that adapting a process style model into the JVM would be easier than adding SNMP monitoring to BEAM. The length of the Barcelona project bibliography suggests otherwise, but we’ll never know unless some brave soul goes and tries to do this. Fortunately, the JDK is open source now. One has to wonder whether such a change could make its way through the JCP, though. Unfortunately for Ted, I found that many of his arguments were weakened by his lack of knowledge about Erlang.
Steve Vinoski (1, 2, 3) – Steve’s articles are more about the reliability aspects of Erlang, and he’s mostly trying to correct Ted’s facts on Erlang. He thinks that Erlang had proven its reliability chops by running for years non-stop. Given the frequency with which Java app servers need to be (or are) bounced, this doesn’t seem that incredible to me.
Patrick Logan (1, 2, 3) – Patrick piled on after Steve and has spent most of his writing trying to correct/challenge Ted’s assertions about Erlang. Patrick thinks that the conventional (i.e. JVM and CLR) runtimes will have problems implementing an Erlang style shared-nothing model, since the pre-existing libraries for those runtimes are not engineered in a shared-nothing manner.
Barry Kelly was an observer of the Neward-Vinosk-Logan discussion, and added some commentary on the impact of VM primitives on things like lift. This is a point which resonates with me, because it seems to me that both languages and language runtimes will need some work to meet the challenges of large scale multicore computing.
Yariv Sadan has done a pile of stuff in Erlang, and supplied his own summary of the differences between Scala and Erlang. There is a very informative exchange between Yariv and lift author David Pollak in the comments of this one.
That’s the short rundown. This is a very interesting problem space — before I turned into database programming language guy in graduate school, I was angling to be a concurrent programming language guy. Along the way to that I got pretty good doses of functional and logic programming, as well as actor programming. That work was in the context of people planning to build (for the day) highly concurrent computers, on the order of 1000′s of processors. Today, multicore hardware is not quite up to that level, but it is approaching it pretty quickly. If there is any force in computing that is likely to precipitate the need for a new programming ecosystem (language, runtime, libraries), I think concurrent programming is it. I also think there is just not enough experience with this problem to have a real sense of what is really going to work. Cliff Click and Brian Goetz were right when they said that we just don’t have a good programming model for this stuff. Absent a model, I don’t know how we can think that we really understand what the runtime needs to deliver.