> Unfortunately in the Ruby world live webservices like this haven't really taken off much yet

And they probably never will, whatwith blocking I/O being the norm and no decent concurrency primitives. Too many better alternatives at this point.

I'm not sure where your opinion comes from and what concurrency primitives you are missing in Ruby, but Node.js simply no concurrency primitives at all and it's doing just fine. The I/O framework I use in that RethinkDB example is Celluloid, which implements actors, a concurrency model that is widely regarded as superior to the callback style.

That they never will has more to do with the general attitude of Rails programmers, and their commitment to the REST request/response model. Libraries that offer more flexible interactions are simply not very visible yet.

Slightly related but not relevant now, Ruby 3.0 is expected to have some concurrency construct fundamentally integrated into the language.

Never did any Ruby, nor Node.js, so take this with a grain of salt.

What I understood the OP to mean, and what I experienced myself, is that a language needs to actively promote (OS-level) async I/O for it to be usable, not just support it. If sync I/O is the default, too many libraries will use it (it's easy and works fine, until it doesn't).

Because Node.js has no threading, async I/O is the only choice. Result: 100% of the libraries are async I/O.

Because Go has M-N threading, all I/O is inherently async for the OS, even if it's sync for the semantic threads. Result: 100% of the libraries are async I/O.

Scala and Java have Futures and all the other goodness you would theoretically need to make async HTTP requests. But, as an example, the official AWS access library (a wrapper around the AWS REST API) is synchronous. Result: communicate with AWS in your backend during a request? Block an OS thread, or write your own AWS library.[1]

Even having async I/O as an option at all splits your language in two. Most libraries will fall in the sync category, and their mere existence lowers the incentive to write an async one. E.g.: if there were no AWS library for Java / Scala, I would be much more keen to write an async one myself. But now? Ah well, // TODO: async, and continue.

This is the beauty of Go and Node.js on the server.

[1] Or choose an unofficial and, I'm rudely assuming, less complete / audited / reliable library.

> All async I/O functions have a corresponding sync version.

They do, but they're widely frowned upon in most applications.

They're completely frowned upon in server-related applications.

I've only really seen them used in cheap build scripts, and now with async/await (via Babel's regenerator transformation), I don't even see that much anymore.

This is exactly my experience as well.

If you provide synchronous, blocking interfaces and no concurrency primitives or expectation of non-blocking functions, IO, etc., people will use them.

In languages where concurrency is a built-in, understood pattern (Go, Erlang/Elixir, Haskell*, to name a few) people don't need to care.

Ruby has the worst of many worlds (sync I/O by default, incredibly expensive memory model, incredibly expensive lambdas, first-class functions aren't normally used beyond the "do block"-- nobody is passing them around, chaining, etc.)- I just don't see the reason to keep trying to squeeze blood from this turnip.

Not to make this discussion personal or anything, I'm curious have you ever worked in Ruby? You say things like "why bother" and "trying to squeeze blood from this turnip" as if you don't understand why someone would love Ruby.

Anyway, I do agree with your argument. Unfortunately Ruby is from the generation of programming languages in which I/O was just seen as an api, so the sane thing was to just map to the system api directly.

JavaScript is from that generation as well but got lucky because its requirement to run in the browser forced it to have I/O fully abstracted.

>Because Node.js has no threading, async I/O is the only choice. Result: 100% of the libraries are async I/O

All async I/O functions have a corresponding sync version.

E.g.

  const buffer = fs.readFileSync(path);

You're right, Node.js has no concurrency primitives, but it has true first-class functions.

Ruby lambdas are an afterthought and far too expensive to use in the same expansive capacity as you would in JS (or literally any functional programming language).

Couple that with the fact that the community just doesn't care, and again, I ask why bother?

The actor model isn't superior to callbacks in any technical capacity, and understand, callbacks are only a (perceived) problem when you don't have something like a language-level async/await to transform them for you.

edit: Add in the (MRI) GIL, and you've got yourself a fairly serious impediment to writing efficient, concurrent code.

The choice of I/O model has nothing to do with Ruby (see eventmachine for a commonly-used evented NIO setup). If you want asynchronous io with an event-driven model, there are good options for most languages.

It has everything to do with Ruby.

With Go, Node.js, Erlang/Elixir, you don't enter the stage assuming that every operation you do is actually going to block others.

Concurrency is not a first-class concept in Ruby (nor Python).

Yes, EventMachine exists. Ok, it's not the standard nor norm, and I would wager most Ruby programmers have heard of it but haven't actually used it.

Even if you're using EventMachine or Twisted, those technologies are infectious (by necessity, not complaining here)- everything you build or use needs to utilize those primitives to work successfully.

In Node.js, the assumption is that nothing will block a calling thread (in favor of asynchronous callbacks).

In Go, the assumption is that goroutines (via a semi-preemptive scheduler) will not block their caller.

In Erlang, the assumption is that processes will not block one another (with a fully preemptive scheduler).

As a fan of Node.js- I will state, not having a widely-accepted, standard interface for building concurrent programs (vs. the soup of callbacks/Promises, associated async/await implementations, coroutines via generator functions) has been a severe detriment to the community.

Matz doesn't do good IO, so we don't do good IO.