CODEWITHSUNDEEP
node.jsmultithreadingpromise
Sammy Roberts
Sammy Roberts

Reputation: 657

Treat async code as threads in Node.js?

Kind of a weird question, Imagine you have a situation where you need to run 10 SYNCRONOUS functions, it doesn't matter when they complete, you just want to know when all 10 are done: I.E.

f1()
f2()
f3()
...
f10()
doStuffWithResult();

Now, If you use promises like so, assuming you have rewrote each as promoises:

Promise.All([f1,f2,f3,f4,f5,f6,f7,f8,f9,f10])
.then(() => {
   doStuffWithResult();
})

Would you see a performance increase? Theoretically, I want to say no because these functions are still synchronous, and everything is still running on one thread.

Thanks!

Upvotes: 0

Views: 54

Answers (1)

jfriend00
jfriend00

Reputation: 707238

Would you see a performance increase?

No, what you are proposing would not be faster.

Promises do not create threads. All they do is provide a cooperative system for keeping track of when asynchronous operations are complete and then notifying interested parties of success or failure. They also provide services for propagating errors when asynchronous operations are nested.

And, your proposed Promise.all() code would not even work. You must pass an array of promises to Promise.all(), not an array of function references. In your example, your functions would not even be called.

And, if you changed your code to something that would actually execute, then it would likely be slower than just calling the synchronous functions directly because you'd be executing promise code and all .then() handlers execute on a future tick (not synchronously).

In node.js, the only way to execute synchronous things in parallel is to launch child processes (that can execute in parallel) or pass the operations to some native code that can use actual OS threads.

Upvotes: 3

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