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Is Node.js really single-threaded?

Santhosh Reddy on July 26, 2020

Many developers wonder at some point in their Node.js programming journey that, is Node.js really single-threaded? If it is, how is it able to do a...
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aminmansuri profile image
hidden_dude •

So does this mean that there's no advantage in running Node on a super beefy 16 core machine?

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Santhosh Reddy •

It's a practice to spawn multiple instances of the app with this type of setup.
Have a look at cluster module.

nodejs.org/api/cluster.html

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haseebsaeed •

To get started with multiple instances, have a look at pm2. You can spawn as many instances as your cpu cores.

pm2.keymetrics.io/

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Wannes Gennar •

Honestly, if you're looking to make use of heavy multithreading; Javascript just isn't the language you should be looking at I'm fraid

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Dennis O'Keeffe •

More an aside, but this was a great Node.js course on Frontend Masters that I did once. It touches on the usage of libuv under the hood for anyone who finds this discussion topic fascinating frontendmasters.com/courses/server...

 
dealloc profile image
Wannes Gennar • • Edited

From what I can tell (correct me if I'm wrong), this uses service workers under the hood.
Those have the problem that you're not able to share memory, so if you want to pass large amounts of data around, you're effectively copying it every time it moves between threads.
While perhaps not problematic for some, I see this cause problems on large scale if you're not careful about what you're passing around; as well as the issue that suddenly you're not passing by reference whereas a regular function call would (for objects etc).

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Pankaj Tanwar •

It's been 6 hours. How to get this out of my head? It's very bad. 😣

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Ranieri Althoff •

Very bad indeed

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Ben Halpern •

I concur

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Ranieri Althoff •

Asynchronous execution does not mean parallel execution. Node runs asynchronous tasks concurrently.

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Santhosh Reddy • • Edited

True to some extent(per each worker). But, offloading multiple tasks to libuv thread pool essentially make it parallel.