期货如何在 Akka 演员中执行

Question

I'm trying to make a background task that performs a network call and stores the response in a database. According to the documentation , background tasks are supposed to use the scheduler within the Akka actor system. I need to run a Future inside of this actor:

    actorSystem.scheduler.scheduleOnce(delay = new FiniteDuration(0, TimeUnit.SECONDS)) {
        val future = network.request()
        future.flatMap(saveToDatabase(_))
    }

Therefore, I have two questions:

1. Is this future guaranteed to get executed (to completion)?
2. Is it possible for other requests to follow up on the status of this task (whether it has finished or not)?

Answer 1

The Future in the future value is returned by the network object, so this object is responsible for executing the code that triggers the Future , not Akka. So you need to look at the documentation for the request call to see what completion guarantees there are for this Future .

The Future returned by the flatMap call uses the default execution context that is in scope when this task is created. But the saveToDatabase call is not guaranteed to be called because the Future can fail and flatMap is only called on success.

If you want to track the status of this task, send messages to a monitoring actor at various points in the execution. Other actors can then ask this monitoring actor about the progress of the task.