Why is LIBUV needed in Node JS?
The libuv module has a responsibility that is relevant for some particular functions in the standard library. for SOME standard library function calls, the node C++ side and libuv decide to do expensive calculations outside of the event loop entirely.They make something called a thread pool that thread pool is a series of four threads that can be used for running computationally intensive tasks such as hashing functions.
By default libuv creates four threads in this thread pool. So that means that in addition to that thread used for the event loop there are four other threads that can be used to offload expensive calculations that need to occur inside of our application. Many of the functions include in the node standard library will automatically make use of this thread pool.
Now the presence of this thread pool is very significant. Well clearly Node.js is not truly single threaded
Libuv also gives node access to the operating system’s underlying file system such as networking. So just as the node standard library has some functions that make use of libuv thread pool it also has some functions that make use of code that is built into the underlying operating system through libuv.
Simple Http request
const https=require(“https”)
const start=Date.now()
https.request(“https://www.google.com”,res=>{
res.on(“data”,()=>{} )
res.on(“end”,()=>{console.log(Date.now()-start) }) }).end()
So in this case libuv sees that we are attempting to make an HTTP request. Neither libuv nor node has any code to handle all of this low level operations that are involved with a network request. Instead libuv delegates the request making to the underlying operating system. So it's actually our operating system that does the real HTTP request Libuv is used to issue the request and then it just waits on the operating system to emit a signal that some response has come back to the request. So because Libuv is delegating the work done to the operating system the operating system itself decides whether to make a new threat or not. Or just generally how to handle the entire process of making the request.
Check the docs below -
https://nodejs.org/en/docs/meta/topics/dependencies/#libuv
Another important dependency is libuv, a C library that is used to abstract non-blocking I/O operations to a consistent interface across all supported platforms. It provides mechanisms to handle file system, DNS, network, child processes, pipes, signal handling, polling and streaming. It also includes a thread pool for offloading work for some things that can't be done asynchronously at the operating system level.
So to sum it up, V8 provides the functionalities related to running JS files, but to use system resources like Network, Files, etc., libuv is used. Also it provides a threading model for accessing the resources mentioned.