I have a basic question about how `isActive` works...

# coroutines

[hannesstruss]

I have a basic question about how isActive works:

fun main(args: Array<String>) = runBlocking {
  val job = Job()

  val pool = newFixedThreadPoolContext(2, "Cool")
  repeat(2) {
    launch(pool, parent = job) {
      startLoop()
    }
  }

  delay(1000)

  println("Canceling")
  job.cancel()

  delay(1000)

  println("End")

  Unit
}

suspend fun startLoop() {
  while (isActive) {
    println("I'm active: ${isActive} in ${Thread.currentThread().name}, my job is cancelled: ${coroutineContext[Job]?.isCancelled}")
    Thread.sleep(500)
  }
}

calling job.cancel() will not terminate the loops. The complete output is:

I'm active: true in Cool-1, my job is cancelled: false
I'm active: true in Cool-2, my job is cancelled: false
I'm active: true in Cool-1, my job is cancelled: false
I'm active: true in Cool-2, my job is cancelled: false
I'm active: true in Cool-2, my job is cancelled: false
I'm active: true in Cool-1, my job is cancelled: false
Canceling
I'm active: true in Cool-1, my job is cancelled: true
I'm active: true in Cool-2, my job is cancelled: true
I'm active: true in Cool-1, my job is cancelled: true
I'm active: true in Cool-2, my job is cancelled: true
End

In my real life situation, instead of Thread.sleep, the coroutine is waiting to read from a blocking queue (poll with timeout). If I use delay(500) instead of sleeping, the coroutines are cancelled properly. Does a Coroutine have to suspend in order for isActive to change?

[Marek Defeciński]

may I ask to what isActive resolves?

[Marek Defeciński]

and coroutineContext ?

[hannesstruss]

oh! good pointer. in the suspend fun it resolves to `NonCancellable`: https://github.com/Kotlin/kotlinx.coroutines/blob/master/core/kotlinx-coroutines-core/src/main/kotlin/kotlinx/coroutines/experimental/NonCancellable.kt#L36

[hannesstruss]

so yeah, that's why it's true.

[Marek Defeciński]

and the coroutineContext is ?

[hannesstruss]

coroutineContext resolves to https://github.com/JetBrains/kotlin/blob/master/libraries/stdlib/src/kotlin/coroutines/experimental/CoroutinesLibrary.kt#L108

[Marek Defeciński]

I wanted to compile myself but is not resolving for me

[hannesstruss]

import kotlinx.coroutines.experimental.Job
import kotlinx.coroutines.experimental.NonCancellable
import kotlinx.coroutines.experimental.NonCancellable.isActive
import kotlinx.coroutines.experimental.delay
import kotlinx.coroutines.experimental.launch
import kotlinx.coroutines.experimental.newFixedThreadPoolContext
import kotlinx.coroutines.experimental.runBlocking
import kotlin.coroutines.experimental.coroutineContext

[hannesstruss]

that's the imports

[Marek Defeciński]

thanks for me that last is not visible

[Marek Defeciński]

I have 1.2.10

[Marek Defeciński]

in gradle

[hannesstruss]

I'm on 1.2.40

[hannesstruss]

When I inline the suspend fun into the launch call, it also works – because I'm accessing isActive and coroutineContext from the CoroutineScope, which resolve to the actual values I need

[Marek Defeciński]

kotlinx-coroutines-core : 0.22.5 fixes that

[Marek Defeciński]

I was on 0.22

[petersommerhoff]

Using while (coroutineContext[Job]!!.isActive) { ... } works for me, you don't want to use NonCancellable.isActive

[petersommerhoff]

That's just always true

[petersommerhoff]

BTW you can also use runBlocking<Unit> { ... } to avoid the awkward return value at the end

[hannesstruss]

Yeah, that works, thanks! Is there no global convenience val for isActive outside of CoroutineScope?