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> Async code can not use synchronous code because this would block it, and prevent it from returning to the event loop. This sounds like a JS-specific issue, w

> Async code can not use synchronous code because this would block it, and prevent it from returning to the event loop. This sounds like a JS-specific issue, where you're not allowed to spawn new threads for historical/implementation reasons? Even in Python and Ruby, where the GILs prevent threads from really running in parallel most of the time, you can still use them to unblock an event loop around a long-running function.

fooyc 10y ago
Using threads to make sync code async defeats the advantages of doing async code in the first place. You are writing async code to avoid threads. If you bring threads in your async code, you get the worse of both worlds: Convoluted code, and thread issues (pool exhaustion and/or thread overhead).
- oconnor663 10y ago
  Of course. Switching back and forth between async and threads can be a bad sign. I didn't mean to say that you should do it all the time, rather just to put some context around this: > You can only call a red function from within another red function. That's really really true in JS. There's no way to call an async function from a sync function, if you need to return its result. You are Capital-S-Screwed if you need to do that. But it's going to far to apply that absolute rule to other languages. When you have threads, it's pretty easy to mix sync and async code. It can be a bad idea, just like having a codebase that's half exceptions and half error returns is usually a bad idea, but you're certainly allowed to do it when it makes sense.
- grzm 10y ago
  Threads and async are orthogonal. Threads allow you to do work in parallel. Async allows you to increase CPU utilization in a single process/thread. writing async code to avoid threads Async can be used in single-process systems. It can make sense to use async techniques to maximize work being done on each process/thread. Working with threads and using async methods can both be complex if you don't have good abstractions for doing so. They can be used together to great effect if you have the right tools.

fooyc 10y ago

Using threads to make sync code async defeats the advantages of doing async code in the first place. You are writing async code to avoid threads. If you bring threads in your async code, you get the worse of both worlds: Convoluted code, and thread issues (pool exhaustion and/or thread overhead).

oconnor663 10y ago
Of course. Switching back and forth between async and threads can be a bad sign. I didn't mean to say that you should do it all the time, rather just to put some context around this: > You can only call a red function from within another red function. That's really really true in JS. There's no way to call an async function from a sync function, if you need to return its result. You are Capital-S-Screwed if you need to do that. But it's going to far to apply that absolute rule to other languages. When you have threads, it's pretty easy to mix sync and async code. It can be a bad idea, just like having a codebase that's half exceptions and half error returns is usually a bad idea, but you're certainly allowed to do it when it makes sense.
grzm 10y ago
Threads and async are orthogonal. Threads allow you to do work in parallel. Async allows you to increase CPU utilization in a single process/thread. writing async code to avoid threads Async can be used in single-process systems. It can make sense to use async techniques to maximize work being done on each process/thread. Working with threads and using async methods can both be complex if you don't have good abstractions for doing so. They can be used together to great effect if you have the right tools.