java - ScheduledExecutorService - Check if scheduled task has already been completed

Question

I have a server side application where clients can request to reload the configuration. If a client request to reload the configuration, this should not be done immediately, but with an delay of 1 minute. If another client also requests to reload the configuration in the same minute, this request should be ignored.

My idea is to schedule a task with a ScheduledExecutorService like:

 ScheduledExecutorService service = Executors.newSingleThreadScheduledExecutor();
 service.schedule(new LoadConfigurationTask(), 1, TimeUnit.MINUTES);

 public class LoadConfigurationTask Runnable {
    public void run() {
      // LoadConfiguration
    }
 }

How can I check if a LoadConfigurationTask has been scheduled, but not executed yet, to be able to ignore further requests until the configuration is reloaded ?

Answer 1

You can simply get a reference to a ScheduledFuture like this:

ScheduledFuture<?> schedFuture = service.schedule(new LoadConfigurationTask(), 1, TimeUnit.MINUTES);

Now with the future, you can check if the task is done:

schedFuture.isDone();

Or even better, check how much time left before the execution will begin:

schedFuture.getDelay(TimeUnit.MINUTES);

There is no need for external variable to track the state.