JobCancellationException StandaloneCoroutine was cancelled

Question

Since we are using Coroutines (1.3.5 used) we have a lot of crash : JobCancellationException - StandaloneCoroutine was cancelled.

I read a lot of thread about theses problems and I tried a lot of solution in production but crashes always occurs.

In all our viewmodels we are using the viewmodelscope so it's ok.

But in our data layer we need to launch a tracking events which are fire and forget task. In first step we used a GlobalScope.launch. I was thinking the CancelletationException was due to this global scope so I removed it and create an extension in the data layer with using a SupervisorJob and a CoroutineExceptionHandler:

private val appScope = CoroutineScope(Dispatchers.Default + SupervisorJob())
private val coroutineExceptionHandler by lazy { CoroutineExceptionHandler { _, throwable -> logw("Error occurred inside Coroutine.", throwable) } }

fun launchOnApp(block: suspend CoroutineScope.() -> Unit) {
    appScope.launch(coroutineExceptionHandler) { block() }
}

But I always saw crashes with this code. Do I need to use cancelAndJoin method? Which strategy I can use with a clean archi and this kind of work please?

Thanks in advance

Answer 1

You can build an extension utility that catches the cancellation exception, and do what you want with it:

fun CoroutineScope.safeLaunch(block: suspend CoroutineScope.() -> Unit): Job {
  return this.launch {
    try {
      block()
    } catch (ce: CancellationException) {
      // You can ignore or log this exception
    } catch (e: Exception) {
      // Here it's better to at least log the exception
      Log.e("TAG","Coroutine error", e)
    }
  }
}

And you can use the extension with a coroutine scope of your choice, for example the global scope:

GlobalScope.safeLaunch{
  // here goes my suspend functions and stuff
}

or any viewmodel scope:

myViewModel.viewModelScope.safeLaunch{
// here goes my suspend functions and stuff
}