Is it multi-threaded in nodejs?

Node.js is a JavaScript runtime environment based on the Chrome V8 engine that can be used for server-side programming. Its single-threaded nature is one of its most notable features, but that doesn't mean Node.js can't handle multiple tasks or data streams.

So in Node.js, does it support multi-threading? In fact, Node.js has only one thread and all I/O requests are asynchronous. This feature makes its performance very efficient when handling concurrent requests.

However, the single thread of Node.js is only reflected in the event loop processing of the main thread, not the number of threads running the code. Node.js uses the libuv library to manage all I/O operations. libuv itself is based on a thread pool. It creates a thread pool based on the number of CPU cores. Each thread is responsible for processing I/O operations and other asynchronous operation events. , and these events are placed in an event queue.

When a request arrives at the Node.js server, Node.js will hand it over to the event loop, and the event loop will issue the request to a thread in the thread pool, and the thread will complete the request. I/O operations. While waiting for the I/O to complete, the thread can execute other JavaScript code.

When the I/O request is completed, the thread will push the event to the event queue, and the event loop will be responsible for processing the events in the queue in the order of registration. If the event is dependent on other events, the event loop will wait for the event to complete before processing other events.

In Node.js, developers can use the cluster module to implement multi-process processing, but this is not multi-threading, but creating multiple processes based on the number of CPU cores to handle different requests.

Therefore, it can be said that there is no real multi-threading in Node.js, but its single-threaded asynchronous I/O feature allows it to easily handle concurrent requests without being blocked by the operating system process/ Limited by the overhead caused by thread context switching. In a recent development, Node.js introduced the worker_threads module, which can create and control true multi-threads at runtime to handle computationally intensive tasks, but it is still in the experimental stage.

In short, Node.js does not involve multi-threading issues, but with the support of event loops and thread pools, it can easily handle complex concurrent requests.

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