Is nodejs representing Reactor or Proactor design pattern?

Question

Many articles online demonstrates nodejs as an example of reactor pattern. Isn't it rather proactor?

As far as I understand, the difference between the two is:

1. reactor handles events in a single thread (synchronously),
2. proactor handles events is multiple threads (asynchronously) with completion callbacks.

For example in this article:

Reactor Pattern is an idea of non-blocking I/O operations in Node.js. This pattern provides a handler(in case of Node.js, a callback function) that is associated with each I/O operation. When an I/O request is generated, it is submitted to a demultiplexer.

Isn't it actually definition of proactor?

Answer 1

The distinction has nothing to do with multithreading. It is as follows:

• Reactor - I want to read from a socket, so I subscribe to a data-is-available kind of event and, and when it fires react to it by synchronously reading the available amount.
• Proactor - I want to read from a socket, so I initiate a reading operation (one that proactively reads the data, without waiting for me to react to it's availability), and subscribe to some kind of read-is-complete notification, wherein the read data is immediately available to me.

Node has both kinds of APIs, e.g. stream.ReadableStream#readable/stream.ReadableStream#read are a Reactor interface, while fs.readFile is a Proactor.