NodeJS中的工人是什么

Question

I've primarily programmed in other programming languages but I have been making a webapp in user NodeJS and have come across a few things that I can't quite get my heard around.

I referred to https://nodejs.org/api/cluster.html#cluster_how_it_works

I found that this explained, well, how NodeJS can cope with large numbers of requests despite Node only being single threaded. However, what confuses me is when it says a port is shared among 'many workers'.

Now if Node is not multithreaded then what exactly are these workers. In java for example you can have multithreaded applications using Completable Futures for example. These cause different threads to take responsibility.

But what is a worker in node if not a thread?

Answer 1

Node can easily handle 10,000 concurrent connections in a single thread (see this answer for details). For some things that are blocking it uses a thread pool but this is transparent to you. Your JavaScript uses a single-threaded event loop in every process.

Keep in mind that nginx, a web server that is known for speed is also single-threaded. Redis, a database that is known for speed is also single-threaded. Multi-threading is good for CPU-bound tasks (when you use one thread per CPU) but for I/O-bound tasks that Node is usually used for, single-threaded event loops work better.

Now, to answer your question - in the context of clusters that the website that you linked to is talking about, a worker is a single process. Every one of those processes still has one single-threaded event loop but there can be many of those processes executing at the same time.

See those answers for more details:

• Which would be better for concurrent tasks on node.js? Fibers? Web-workers? or Threads?
• what is mean by event loop in node.js ? javascript event loop or libuv event loop?
• How many clients can an http-server can handle?