kotlin coroutine switching rule?

Question

I want to make two process daemons like aGroup and bGroup. However, bGroup's never started when aGroup doesn't have dealy anyone can tell me why it happened? and what is the best way to make daemon which running forever with coroutine.

thanks

@Test
fun `test`() {
    runBlocking {

        val one = async(start = CoroutineStart.LAZY) {
            while (true) {
                runAGroup();
            }
        }.start()

        (1..10).forEach {

            async(start = CoroutineStart.LAZY) {

                while (true) {
                    runBGroup(it)
                }

            }.start()
        }
    }
}


suspend fun runAGroup() {
    println("[AGroup] Main")
    // delay(1000L)  <--- here
}

suspend fun runBGroup(name: Int) {
    println("[BGrouop] $name (1000L)")
    delay(1000L)

}

Answer 1

runBlocking without an explicit dispatcher uses an event loop to dispatch between coroutines. Because your runGroupA runs without interruptions there is no chance for other coroutines to run. If you specify a other Dispatcher eg Dispatchers.Default you will see that the other coroutine runs as well.

runBlocking(Dispatchers.Default) {
    val one = async(start = CoroutineStart.LAZY) {
        while (true) {
            runAGroup();
        }
    }.start()

    (1..10).forEach {

        async(start = CoroutineStart.LAZY) {

            while (true) {
                runBGroup(it)
            }

        }.start()
    }
}