In Scala Monix Scheduler how to propagate exceptions to main program?

Question

I have a Monix Scheduler that scheduling error-prone task:

import scala.concurrent.duration._
import monix.eval.Task
import monix.execution.Scheduler
import java.time._

scheduler.scheduleWithFixedDelay(0.seconds, 1.seconds) {
    IO(println("qq"))
        .map{ _ => 
            if (Instant.now.getEpochSecond % 5 == 0) 
                throw new Exception()
        }
        .unsafeRunSync()
}

The problem is -- if the task inside scheduler throw exception, the scheduler stops and exception does not propagate to main program. I want the main program get the exception and handle it (in fact I want to stop the whole program.).

I may well just call sys.exit() inside, but I think it is not ideal because parent process should supervise the child process.

When using Task I can catch it from main program by task.runSyncUnsafe() , for Scheduler is there way to do the same thing ?

Answer 1

You can't catch exception because the scheduler runs asynchronously.

If you are using cats-effect IO (or monix Task), you could use .attempt, and then left map on the Either to handle exceptions. But you have to explicitly cancel the scheduled job.