Retrieves or creates a new Scheduler.Worker that represents serial execution of actions.

When work is completed it should be unsubscribed using Scheduler.Worker#unsubscribe().

Work on a Scheduler.Worker is guaranteed to be sequential.

Returns:Scheduler.Worker

a Worker representing a serial queue of actions to be executed

Gets the current time, in milliseconds, according to this Scheduler.

Returns:long

the scheduler's notion of current absolute time in milliseconds

Allows the use of operators for controlling the timing around when actions scheduled on workers are actually done. This makes it possible to layer additional behavior on this Scheduler. The only parameter is a function that flattens an Observable of Observable of Completables into just one Completable. There must be a chain of operators connecting the returned value to the source Observable otherwise any work scheduled on the returned Scheduler will not be executed.

When Scheduler#createWorker() is invoked a Observable of Completables is onNext'd to the combinator to be flattened. If the inner Observable is not immediately subscribed to an calls to Worker#schedule are buffered. Once the Observable is subscribed to actions are then onNext'd as Completables.

Finally the actions scheduled on the parent Scheduler when the inner most Completables are subscribed to.

When the Worker is unsubscribed the Completable emits an onComplete and triggers any behavior in the flattening operator. The Observable and all Completables give to the flattening function never onError.

Limit the amount concurrency two at a time without creating a new fix size thread pool:

Scheduler limitScheduler = Schedulers.computation().when(workers -> {
    // use merge max concurrent to limit the number of concurrent
    // callbacks two at a time
    return Completable.merge(Observable.merge(workers), 2);
});

This is a slightly different way to limit the concurrency but it has some interesting benefits and drawbacks to the method above. It works by limited the number of concurrent Workers rather than individual actions. Generally each Observable uses its own Worker. This means that this will essentially limit the number of concurrent subscribes. The danger comes from using operators like Observable#zip(Observable, Observable, rx.functions.Func2) where subscribing to the first Observable could deadlock the subscription to the second.

Scheduler limitScheduler = Schedulers.computation().when(workers -> {
    // use merge max concurrent to limit the number of concurrent
    // Observables two at a time
    return Completable.merge(Observable.merge(workers, 2));
});

Scheduler slowScheduler = Schedulers.computation().when(workers -> {
    // use concatenate to make each worker happen one at a time.
    return Completable.concat(workers.map(actions -> {
        // delay the starting of the next worker by 1 second.
        return Completable.merge(actions.delaySubscription(1, TimeUnit.SECONDS));
   }));
});

Parameters

<S>

a Scheduler and a Subscription

combine:Func1<Observable<Observable<Completable>>, Completable>

the function that takes a two-level nested Observable sequence of a Completable and returns the Completable that will be subscribed to and should trigger the execution of the scheduled Actions.

Returns:S

the Scheduler with the customized execution behavior

Annotations

@SuppressWarnings:unchecked

Since

1.3