Hi folks, I'm using `newSingleThreadExecutor` as a Dispatcher but I have a problem with it, when I u...

# coroutines

[SrSouza]

Hi folks, I'm using newSingleThreadExecutor as a Dispatcher but I have a problem with it, when I use delay(x) , other functions that use the same dispatcher does not execute until the delay finish. Why this is happening if delay does not block the Thread.

[octylFractal]

can't reproduce, can you show code?

[octylFractal]

fun main() {
    val dispatcher = Executors.newSingleThreadExecutor().asCoroutineDispatcher()
    runBlocking(dispatcher) {
        launch {
            println("Foo!")
            delay(1000L)
            println("After Foo!")
        }
        launch {
            println("Bar!")
            delay(1000L)
            println("After Bar!")
        }
    }
}

produced:

Foo!
Bar!
After Foo!
After Bar!

[SrSouza]

I fix it. The problem was that I have something like this:

withContext(singleThread) {
   coroutineScope.launch(singleThread) {
      delay(x)
   }
}

When I migrate it to a function thar produce a Job, fix the problem, But why ?

[elizarov]

withContext suspends until all the coroutines launched in its scope complete.

[SrSouza]

Good to know that, tkx Roman.

[EyeCon]

Just for may understanding: coroutineScope {} also does that, right? So it is only async and launch that fire off jobs that are executed in parallel, while a scope ending of coroutineScope or withContext suspends until every child coroutine is completed.

[octylFractal]

yes, that's correct -- though it is incorrect to say only async and launch start parallel jobs, other things like produce, actor, and Flow.launchIn can also do so -- many methods that take a coroutine scope and aren't suspend will start a separate job

[EyeCon]

Thanks a lot!