Hi guys, I have a question. I know that when you launch coroutines, Kotlin is nice enough that wants...

# coroutines

[Andrea Giuliano]

Hi guys, I have a question. I know that when you launch coroutines, Kotlin is nice enough that wants to keep structured concurrency such that if a coroutine in a context fails, than all the running coroutines gets cancelled.

runBlocking {
  launch { dosomething }
  launch { throw Exception }
}

This is nice because it make your thinking easier, and you are pretty much saying: here’s all I need to do, do that in parallel and in case something happens fail everything.

Now my question is this: what if I want to launch many coroutines that are independent from each other? I take the example of threadpool when on many threads you launch some operation but one thread throwing exception does not affect the others. Imagine that on each coroutine I’m handling a separate http request for example.
From the official doc, apart from handling explicitly the exception handling, I haven’t seen any of such examples and I wonder: is the price of launching coroutines that easy paid off when you really want to go in parallel with no noisy neighbours?

[Andrea Giuliano]

maybe I can answer myself saying that I should be doing something like this

runBlocking {
  coroutineScope { launch { dosomething }}
  coroutineScope { launch { throw Exception } }
}

and this isolates the scope of the different coroutines but still make them running on the same dispatcher/context

[Zach Klippenstein (he/him) [MOD]]

CoroutineScope will not return until all child coroutines have completed, so this is actually less concurrent than your original code.

[Zach Klippenstein (he/him) [MOD]]

If you want your launch coroutines to outlive the current scope, you need to explicitly provide another scope to launch them in.

[Andrea Giuliano]

right! would that make them independent from an exception handling point of view?

[Zach Klippenstein (he/him) [MOD]]

Independent of the current scope, yes.

[Zach Klippenstein (he/him) [MOD]]

If you want one coroutine's failure to not cancel its siblings, use SupervisorJob/supervisorScope