[SomeCallMeTim]

Strawman.

For tasks that are primarily IO bound, async architectures can scale more than synchronous languages. Period.

It would take intentionally (or newb/cluelessly) bad design to end up with a Node server that DOSed at 12 connections per second.

In PHP, if you run 4 threads, it just takes a backend with a 333ms latency (on all queries performed serially) to limit you to 12 connections per second. If you only run one thread, you just need a backend with a cumulative 83ms latency to get DOSed at 12 connections per second. In a more realistic scenario, a typical crappy framework will result in dozens of queries for a single page, but it comes down to the same thing.

In Node, you can run one thread with a cumulative 333ms backend latency and still handle thousands of connections per second. They'll each just end up waiting a bit more than 333ms for their results, assuming the database itself isn't DOSed (which takes a surprisingly high load -- way above the levels we're talking). Actually, depending on how interconnected the backend queries are, Node may actually result in less than a total 333ms latency, because many of those queries may also be parallelized by the browser, and will then be handled in parallel by the server (and much of the latency may actually be in http negotiations and/or establishing a database connection, honestly).

[tyingq]

>>It would take intentionally (or newb/cluelessly) bad design to end up with a Node server that DOSed at 12 connections per second.

Single threaded makes for it's own pitfalls. I assume you can imagine some cpu bound tasks that would have node.js at 12 connections/sec or less.

[SomeCallMeTim]

>I assume you can imagine some cpu bound tasks that would have node.js at 12 connections/sec or less.

Certainly. That would fall under "newb/clueless" design, though. Anyone who would throw a CPU-bound task into a primary Node server shouldn't be allowed near architectural design decisions. Whereas code in PHP written using best practices can easily end up with a server that can barely hit 100 queries per second.

Imagine, for instance, a situation where the client needs to do 50 requests to the server to render a page [1][2], and each query ends up with 20ms of latency on the PHP side; assuming you're running 8 threads (and the client makes 8 concurrent requests), a single page query could block your server for 125ms. A slow client or network might even block your PHP threads for longer. Node could crunch through ten thousand requests like that per second when running on four CPUs, meaning 125 of these bloated pages rendered per second, compared to ... 8 or less.

Even with decent client pages that can render with ONE server query, a couple dozen database lookups are par for the course, sometimes including an authentication lookup on a third-party OAUTH server. That could be 125ms all by itself, and in PHP your thread is blocked while the lookup happens. With the async model, once the query is off, the server is doing work on other requests until the query has returned data.

Many CPU-bound tasks like "convert an image" are already coded in Node to happen in the background, triggering a callback when they're done so you can then send the result to the client. And in Node it's absolutely trivial to offload any likely CPU-bound task to a microservice, where the NodeJS server just queries the microservice and waits for the result. Which you'd want to do, of course, if a task is CPU-bound, because you would want a faster server than V8 running it anyway. Go would be a likely candidate, and Go handles threading either through light/async threads or via actual threading, as necessary. It's quite awesome.

And if you really can't trust your developer to write code without extensive time-consuming calculations, then make them use Elixir or Erlang. It will use preemptive multitasking at the VM level if a thread takes up too much time, and even if they foolishly write a task that takes hundreds of milliseconds to complete, it will still task swap and serve other clients.

But arguing that pathologically bad code in Node can make it perform as badly as PHP does all the time isn't exactly a ringing endorsement for the language.

[1] In 2014 the average number of objects a web page requested was 112, and seemed to continue to be going up, though I'm assuming a lot of those are static resources and third party requests, like for analytics and ads. http://www.websiteoptimization.com/speed/tweak/average-web-p... I've personally seen pages with 70-80 requests against a PHP backend to render one page.

[2] And I wouldn't call a client page needing 50 requests a best practice, but I'm assuming that we're talking about the server side here, and that we are being forced to deal with an existing client that behaves that way. So call it "best practices on the server."