Every article on this sort of thing seems to just gloss over this part. Why isn't one CPU enough? What is using it? Serving static files certainly won't. Doing simple things won't...
Does anyone have any use cases / experience for when this was the case? :/
edit: Fine downmodding fanboys. I get it. Use whatever you like. Meh
That said Node is a programming environment so the question is, when on a multi-core machine (which all DC machines are) how can we scale to use all the cores so we can do much harder stuff.
What about a node system to deal with 100k concurrent long-poll connections? When some of those are active they could be really active, requiring all the cores, etc. There are lots of scenarios in which more compute power is useful.
Networking IO isn't CPU heavy. There's no reason to increase complexity and slow throughput in the hope that more CPUs will help...
Not saying I agree with the design choices (I'm more of a multiple language / "hard and soft layers" person, and I don't care for Javascript), but I think that's the reason.
The article mentions that using NodeJS as a simple HTTP proxy with no application logic can sustain only 2100 reqs/s before a 2.5GHz Xeon is maxed out. NodeJS uses CPU more efficiently than other HTTP stacks, but its I/O engine is not infinitely scalable.
That sounds fairly lame to me. Proxying network traffic isn't a CPU heavy operation. Worst case you have to move a few bits of memory around.