Is awaitAll workitg as expected here? I have 10 Deferred in my responses list (highlighted in termin...

# coroutines

[gammanik]

Is awaitAll workitg as expected here?
I have 10 Deferred in my responses list (highlighted in terminal). The weird thind that they all are marked as completed.
But I can iterate only to a lesser amount at the end. There are only 3 in the output.

BTW if I uncomment //delay(6000) I’ll see all 10 responses
What am I doing wrong?

[tseisel]

This may be related to awaiting i a different runBlocking block than the one where you launched your async coroutines.
On what dispatcher are you launching coroutines ? Is it single-threaded ?
Be aware that you should try to avoid using `runBlocking`: it has been designed to bridge normal code to the coroutine world in specific situations, for example the main function.

[gammanik]

I’m calling it from main function and I wasn’t setting a dispatcher explicidly. This is the only one runBlocking in the program

[tseisel]

Could you please share the declaration of the responses variable (that I expect to be of type List<Deferred<Collection<Person>>>) ?

[gammanik]

Sure:

val responses: ArrayList<Deferred<Collection<Person>>> = ArrayList()

[gammanik]

for (passenger in passengers) {
    val suggestedDrivers = suggestDriversAsync(passenger, drivers)
    println("Passenger point: ${passenger.finishPoint.latitude}, ${passenger.finishPoint.longitude}")

    GlobalScope.launch {
        responses.add(suggestedDrivers)
    }
}

runBlocking {
    val res: List<Collection<Person>> = responses.awaitAll()
    for (el in res) {
        println(el)
    }
}

[tseisel]

Some remarks:
1. You should try to wrap the whole code in runBlocking, for example

fun main() = runBlocking<Unit> {
    val responses = ...
    [...]
    val res = responses.awaitAll()
}

2. Why launch a coroutine in GlobalScope to add suggestedDrivers to the list ? Its not an operation that requires calling suspend functions

[gammanik]

suggestDriversAsync returns Deferred<Collection<Person>>
If I wrap the whole code in runblocking I’ll send requests syncroniously I guess.

So I wanted to send all the requests at once and then wait when they all are gonna be finished

[tseisel]

I wrote this sample based on your code
https://pl.kotl.in/N0HVVa2T5

[gammanik]

Thank you! Great example.
I’ve just added <http://Dispatchers.IO|Dispatchers.IO> to async and now it’s perfect