Would this work as a system that allows callers to...

# coroutines

[Zoltan Demant]

Would this work as a system that allows callers to either send a signal ("flush"), or await the next signal that arrives? The calls come from different scope.launch blocks that are running in parallell.

@JvmInline
internal value class Queue(
    private val trigger: MutableSharedFlow<Unit> = MutableSharedFlow(extraBufferCapacity = 8),
) {

    suspend fun flush() {
        trigger.emit(Unit)
    }

    suspend fun await() {
        trigger.first()
    }
}

[Joffrey]

Why the extra buffer?

[Zoltan Demant]

What would be the difference in not using one?

From my understanding, having one prevents trigger.emit from suspending (unless exceeding 8 elements). This seems ideal for my use-case, but Im not sure it makes any difference given the trigger.first call.

[Zoltan Demant]

Sorry, I wrote this code a couple of months ago (just investigating a bug now). I think what I was going for with the buffer is that if one client uses flush, it shouldnt be blocked until another client uses await. I believe this is what happens?

[Zoltan Demant]

I guess the buffer doesnt matter due to the collector just being flow.first()? Just to verify that Ive understood things correctly, that also means that if I replace flow.first() with flow.collect{ delay(5000) } then the emit will also take 5000 ms?

[Joffrey]

Technically any flush() call will immediately complete (and the event immediately discarded) as long as no consumer is await()-ing. And given that consumers just use first(), it's also pretty quick when one is waiting. That said, without the buffer, flush() callers would indeed suspend if a consumer is waiting (albeit not for long).

I was just wondering whether this was intentional

[Zoltan Demant]

Seems like my understanding was not 100% on point, so thank you for helping me learn something new today!