Dude, I've been developing real-time military applications and we've moved from C/C++ to Java and got performance gains (I'm not saying that C can't beat Java doing specific computations - of course it can - but when building a large application with millions of lines of code and a large team of developers, Java would be a safer bet than C++ if speed is your concern). In other words, no other environment can beat the JVM.

And, yeah, you should try Clojure. It's a cathartic experience.

EDIT: The only doubts I have about vert.x is that it can consistently beat "old" JVM servlet containers under heavy, real-world loads. That remains to be seen.

(I'm not actually serious about the last bit).

importPackage(java.io); var file = new File('/blah/blah/blah.txt');

Other languages would be equally easy as well. It's burried, but here is some relevant information from the docs on integrating 3rd party libs:

-cp <path> The path on which to search for the main and any other resources used by the verticle. This is ignored if you are running an installed module. This defaults to . (current directory). If your verticle references other scripts, classes or other resources (e.g. jar files) then make sure these are on this path. The path can contain multiple path entries separated by : (colon). Each path entry can be an absolute or relative path to a directory containing scripts, or absolute or relative filenames for jar or zip files. An example path might be -cp classes:lib/otherscripts:jars/myjar.jar:jars/otherjar.jar Always use the path to reference any resources that your verticle requires. Please, do not put them on the system classpath as this can cause isolation issues between deployed verticles.

Assumed I use this ImageIO package. Will it be nonblocking, concurrent and spread to all my cores automagically with Vert.x??

As far as concurrency, most libraries state in the docs what is threadsafe and what is not, so this is more or less "caveat emptor" and RTFM.

Vert.x has its own module subsystem which appears to package up .jar files and some glue code for the Vert.x-specific interface, but I assume you can call any included Java classes directly: http://vertx.io/mods_manual.html

(Interestingly enough, Vert.x uses Gradle for its build/dependency manager, but I guess wanted something more Node-like for its module system)

By using a Java JDBC database driver you're completely losing any async support. Same presumably goes for redis or Mongo drivers. You can do some of the work with threads and pooling, but it's still not the same, and makes this another useless micro benchmark.

The jvm has amazing threading support, doubly so if you use it with a language like scala or clojure. You can and should handle the connections asynchronously and use a thread pool for things like db access. It works well, people have done this with the jvm for years.

You don't actually get a performance boost from Node being "async". Node's async abilities simply give you transparent access to threads that are otherwise unavailable with javascript, and it's the threads giving you performance.

The async API is actually a price to pay (spaghettification).

For example, the go language took a different approach: it created a cheap thread-like construct which doesn't incur in the biggest overhead of classical threading (namely pre-allocated linear stacks and context switching/sleeping requiring a systemcall; all this aided by the compiler), and a cheap mean of communication (channels).

Then, the whole core IO library was written using a multiplexing async model (epoll...), which communicates with the user part of the library via channels). The result is a blocking like API which under the hood behaves like an async implementation.

A similar goal is also met by http://www.neilmix.com/narrativejs/doc/ and other javascript 'weavers' which convert "sequantial looking" code into callbacks.

It's been found that if you employ only a single thread (that can run any number of tasks) you get a performance boost over using a larger threadpool under some conditions, but a single thread wouldn't let you scale by taking advantage of all processors.

Async IO is different, it's a different patter of access to IO and as such it's orthogonal to any threading or multiprocessing that's going on in order to actually do stuff in response to that IO.

> It's been found that if you employ only a single thread (that can run any number of tasks) you get a performance boost over using a larger threadpool under some conditions, but a single thread wouldn't let you scale by taking advantage of all processors.

Indeed. Nodejs solution to this problem is to have a cluster of nodejs processes and a dispatcher process on top. So multiprocessing is done the "old way".

It has both event loops and a background thread pool, so you can choose which to run your task on depending on what kind of thing it is.

E.g. it's stupid to run long running or blocking actions on an event loop.

You say that like it's a good thing. I'd much rather have the choice between async and sync.

Sure programming-wise it's nice to have sync. No argument there.

Yes, that's exactly Node's main selling proposition everybody forgets when presenting their next Node.js

Other platforms/languages have real concurrency constructs and don't suffer node's limitations.

I don't know whether making JS single-threaded was a principled decision -- if anything it was presumably the KISS principle at work. However, it was actually a ridiculously nice choice to offer a single-threaded-asynchrony model. It sometimes gets in the way rather obtusely -- Firefox can still (if very rarely) fail to introspect and then crash when some ad script on your page goes into an infinite loop! -- but on the whole, it is very nice to always know that while I'm in this function, modifying this variable, nobody else can interfere.

With that said, I also think that the lack of good concurrency planning is indeed missing, and that it will probably enter the language at a future time.

At best it's "making a virtue out of necessity".

Sounds like you're quoting from the "Node.js Is Bad Ass Rock Star Tech" satire video ( http://www.youtube.com/watch?v=bzkRVzciAZg ).

Nothing inherently special about "forcing the entire ecosystem to be async too", especially since Node is more or less FORCED to do that, because javascript is single threaded.

Add the bad callback spaghetti implementation of async, and the main benefit of Node is easy deployment, and accessibility to the millions of javascript programmers.

As an async environment it doesn't offer anything either new or too compelling.

That isn't strictly true.

If you focus on the traditional scripting languages as your competition: Ruby, Python, PHP, Perl: Then you start to realise that Node.js does offer a similar language structure (dynamic, no compilation, etc), with the benefits of thousands of concurrent connections (which those languages will do with certain modules) but while forcing all the libraries to also be async (which those languages DO NOT do).

At my last job I had to build an SMTP server capable of scaling to 50k concurrent connections. Building this in Perl was fine, except for any library I wanted to use - all of the libraries were synchronous. So now I wrote Haraka, which Craigslist are now using as their incoming SMTP server.

If you compare all that to Java you get slightly less performance but probably lower memory requirements. And that's OK. Different strokes for different folks.

What? What do you mean by non blocking in this context?

Well, this is the JVM, not a single threaded javascript engine. As the other guy says below:

"You don't need to necessarily have non-blocking libraries to take advantage of the async I/O. Netty uses worker threads to prevent blocking the server event loop and I assume Vert.X does as well. You can do blocking JDBC queries, Redis, etc."

And threadsafe libs --of which are tons--, usually advertise it on "the box.