Thread in an event-driven vs non-event driven web server
node.js
Solution
Node may use threads for IO. The JS code runs in a single thread, but all the IO requests are running in parallel threads. If you want some JS code to run in parallel threads, use thread-a-gogo or some other packages out there which mitigate that behaviour.
Same as `1.`, threads are created by Node for IO operations.
You don't have to handle threading, unless you want to. Easier to develop. At least that's my point of view.
A node application can be coded to run like another web server. Typically, JS code runs in a single thread, but there are ways to make it behave differently.
Personally, I recommend threads-a-gogo (the package name isn't that revealing, but it is easy to use) if you want to experiment with threads. It's faster. Node also supports multiple processes, you may run a completely separate process if you also want to try that out.
Problem
The following two diagrams are my understanding on how threads work in a event-driven web server (like Node.js + JavaScript) compared to a non-event driven web server (like IIS + C#) From the diagram is easy to tell that on a traditional web server the number of threads used to perform 3 long running operations is larger than on a event-driven web server (3 vs 1.) I think I got the "traditional web server" counts correct (3) but I wonder about the event-driven one (1). Here are my questions: Is it correct to assume that only one thread was used in the event-driven scenario? That can't be correct, something must have been created to handle the I/O tasks. Right? How did the evented server handled the I/O? Let's say that the I/O was to read from a database. I suspect that the web server had to create a thread to hand off the job of connecting to the database? Right? If the event-driven web server indeed created threads to handle the I/O where is the gain? A possible explanation for my confusion could be that on both scenarios, traditional and event-driven, three separate threads were indeed created to handle the I/O (not shown in the pictures) but the difference is really on the number of threads on the web server per-se, not on the I/O threads. Is that accurate?