* The associated system parameter, {@code rx.scheduler.drift-tolerance}, expects its value in minutes. */ static final long CLOCK_DRIFT_TOLERANCE_NANOSECONDS; static { CLOCK_DRIFT_TOLERANCE_NANOSECONDS = TimeUnit.MINUTES.toNanos( Long.getLong("rx2.scheduler.drift-tolerance", 15)); } /** * Returns the clock drift tolerance in nanoseconds. *
Related system property: {@code rx2.scheduler.drift-tolerance} in minutes * @return the tolerance in nanoseconds * @since 2.0 */ public static long clockDriftTolerance() { return CLOCK_DRIFT_TOLERANCE_NANOSECONDS; } /** * Retrieves or creates a new {@link Scheduler.Worker} that represents serial execution of actions. *
* When work is completed it should be unsubscribed using {@link Scheduler.Worker#dispose()}. *
* Work on a {@link Scheduler.Worker} is guaranteed to be sequential. * * @return a Worker representing a serial queue of actions to be executed */ @NonNull public abstract Worker createWorker(); /** * Returns the 'current time' of the Scheduler in the specified time unit. * @param unit the time unit * @return the 'current time' * @since 2.0 */ public long now(@NonNull TimeUnit unit) { return unit.convert(System.currentTimeMillis(), TimeUnit.MILLISECONDS); } /** * Allows the Scheduler instance to start threads * and accept tasks on them. *
Implementations should make sure the call is idempotent and thread-safe. * @since 2.0 */ public void start() { } /** * Instructs the Scheduler instance to stop threads * and stop accepting tasks on any outstanding Workers. *
Implementations should make sure the call is idempotent and thread-safe. * @since 2.0 */ public void shutdown() { } /** * Schedules the given task on this scheduler non-delayed execution. * *
* This method is safe to be called from multiple threads but there are no * ordering guarantees between tasks. * * @param run the task to execute * * @return the Disposable instance that let's one cancel this particular task. * @since 2.0 */ @NonNull public Disposable scheduleDirect(@NonNull Runnable run) { return scheduleDirect(run, 0L, TimeUnit.NANOSECONDS); } /** * Schedules the execution of the given task with the given delay amount. * *
* This method is safe to be called from multiple threads but there are no * ordering guarantees between tasks. * * @param run the task to schedule * @param delay the delay amount, non-positive values indicate non-delayed scheduling * @param unit the unit of measure of the delay amount * @return the Disposable that let's one cancel this particular delayed task. * @since 2.0 */ @NonNull public Disposable scheduleDirect(@NonNull Runnable run, long delay, @NonNull TimeUnit unit) { final Worker w = createWorker(); final Runnable decoratedRun = RxJavaPlugins.onSchedule(run); DisposeTask task = new DisposeTask(decoratedRun, w); w.schedule(task, delay, unit); return task; } /** * Schedules a periodic execution of the given task with the given initial delay and period. * *
* This method is safe to be called from multiple threads but there are no * ordering guarantees between tasks. * *
* The periodic execution is at a fixed rate, that is, the first execution will be after the initial * delay, the second after initialDelay + period, the third after initialDelay + 2 * period, and so on. * * @param run the task to schedule * @param initialDelay the initial delay amount, non-positive values indicate non-delayed scheduling * @param period the period at which the task should be re-executed * @param unit the unit of measure of the delay amount * @return the Disposable that let's one cancel this particular delayed task. * @since 2.0 */ @NonNull public Disposable schedulePeriodicallyDirect(@NonNull Runnable run, long initialDelay, long period, @NonNull TimeUnit unit) { final Worker w = createWorker(); final Runnable decoratedRun = RxJavaPlugins.onSchedule(run); PeriodicDirectTask periodicTask = new PeriodicDirectTask(decoratedRun, w); Disposable d = w.schedulePeriodically(periodicTask, initialDelay, period, unit); if (d == EmptyDisposable.INSTANCE) { return d; } return periodicTask; } /** * 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 {@link Scheduler}. The only parameter * is a function that flattens an {@link Flowable} of {@link Flowable} * of {@link Completable}s into just one {@link Completable}. There must be * a chain of operators connecting the returned value to the source * {@link Flowable} otherwise any work scheduled on the returned * {@link Scheduler} will not be executed. *
* When {@link Scheduler#createWorker()} is invoked a {@link Flowable} of * {@link Completable}s is onNext'd to the combinator to be flattened. If * the inner {@link Flowable} is not immediately subscribed to an calls to * {@link Worker#schedule} are buffered. Once the {@link Flowable} is * subscribed to actions are then onNext'd as {@link Completable}s. *
* Finally the actions scheduled on the parent {@link Scheduler} when the * inner most {@link Completable}s are subscribed to. *
* When the {@link Worker} is unsubscribed the {@link Completable} emits an * onComplete and triggers any behavior in the flattening operator. The * {@link Flowable} and all {@link Completable}s 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(Flowable.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 {@link Worker}s rather than individual * actions. Generally each {@link Flowable} uses its own {@link Worker}. * This means that this will essentially limit the number of concurrent * subscribes. The danger comes from using operators like * {@link Flowable#zip(org.reactivestreams.Publisher, org.reactivestreams.Publisher, io.reactivex.functions.BiFunction)} where * subscribing to the first {@link Flowable} could deadlock the * subscription to the second. * *
* Scheduler limitScheduler = Schedulers.computation().when(workers -> {
* // use merge max concurrent to limit the number of concurrent
* // Flowables two at a time
* return Completable.merge(Flowable.merge(workers, 2));
* });
*
*
* Slowing down the rate to no more than than 1 a second. This suffers from
* the same problem as the one above I could find an {@link Flowable}
* operator that limits the rate without dropping the values (aka leaky
* bucket algorithm).
*
*
* 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));
* }));
* });
*
*
* History: 2.0.1 - experimental
* @param
* Disposing the {@link Worker} cancels all outstanding work and allows resource cleanup.
*/
public abstract static class Worker implements Disposable {
/**
* Schedules a Runnable for execution without delay.
*
* The default implementation delegates to {@link #schedule(Runnable, long, TimeUnit)}.
*
* @param run
* Runnable to schedule
* @return a Disposable to be able to unsubscribe the action (cancel it if not executed)
*/
@NonNull
public Disposable schedule(@NonNull Runnable run) {
return schedule(run, 0L, TimeUnit.NANOSECONDS);
}
/**
* Schedules an Runnable for execution at some point in the future.
*
* Note to implementors: non-positive {@code delayTime} should be regarded as non-delayed schedule, i.e.,
* as if the {@link #schedule(Runnable)} was called.
*
* @param run
* the Runnable to schedule
* @param delay
* time to wait before executing the action; non-positive values indicate an non-delayed
* schedule
* @param unit
* the time unit of {@code delayTime}
* @return a Disposable to be able to unsubscribe the action (cancel it if not executed)
*/
@NonNull
public abstract Disposable schedule(@NonNull Runnable run, long delay, @NonNull TimeUnit unit);
/**
* Schedules a cancelable action to be executed periodically. This default implementation schedules
* recursively and waits for actions to complete (instead of potentially executing long-running actions
* concurrently). Each scheduler that can do periodic scheduling in a better way should override this.
*
* Note to implementors: non-positive {@code initialTime} and {@code period} should be regarded as
* non-delayed scheduling of the first and any subsequent executions.
*
* @param run
* the Runnable to execute periodically
* @param initialDelay
* time to wait before executing the action for the first time; non-positive values indicate
* an non-delayed schedule
* @param period
* the time interval to wait each time in between executing the action; non-positive values
* indicate no delay between repeated schedules
* @param unit
* the time unit of {@code period}
* @return a Disposable to be able to unsubscribe the action (cancel it if not executed)
*/
@NonNull
public Disposable schedulePeriodically(@NonNull Runnable run, final long initialDelay, final long period, @NonNull final TimeUnit unit) {
final SequentialDisposable first = new SequentialDisposable();
final SequentialDisposable sd = new SequentialDisposable(first);
final Runnable decoratedRun = RxJavaPlugins.onSchedule(run);
final long periodInNanoseconds = unit.toNanos(period);
final long firstNowNanoseconds = now(TimeUnit.NANOSECONDS);
final long firstStartInNanoseconds = firstNowNanoseconds + unit.toNanos(initialDelay);
Disposable d = schedule(new PeriodicTask(firstStartInNanoseconds, decoratedRun, firstNowNanoseconds, sd,
periodInNanoseconds), initialDelay, unit);
if (d == EmptyDisposable.INSTANCE) {
return d;
}
first.replace(d);
return sd;
}
/**
* Returns the 'current time' of the Worker in the specified time unit.
* @param unit the time unit
* @return the 'current time'
* @since 2.0
*/
public long now(@NonNull TimeUnit unit) {
return unit.convert(System.currentTimeMillis(), TimeUnit.MILLISECONDS);
}
/**
* Holds state and logic to calculate when the next delayed invocation
* of this task has to happen (accounting for clock drifts).
*/
final class PeriodicTask implements Runnable {
@NonNull
final Runnable decoratedRun;
@NonNull
final SequentialDisposable sd;
final long periodInNanoseconds;
long count;
long lastNowNanoseconds;
long startInNanoseconds;
PeriodicTask(long firstStartInNanoseconds, @NonNull Runnable decoratedRun,
long firstNowNanoseconds, @NonNull SequentialDisposable sd, long periodInNanoseconds) {
this.decoratedRun = decoratedRun;
this.sd = sd;
this.periodInNanoseconds = periodInNanoseconds;
lastNowNanoseconds = firstNowNanoseconds;
startInNanoseconds = firstStartInNanoseconds;
}
@Override
public void run() {
decoratedRun.run();
if (!sd.isDisposed()) {
long nextTick;
long nowNanoseconds = now(TimeUnit.NANOSECONDS);
// If the clock moved in a direction quite a bit, rebase the repetition period
if (nowNanoseconds + CLOCK_DRIFT_TOLERANCE_NANOSECONDS < lastNowNanoseconds
|| nowNanoseconds >= lastNowNanoseconds + periodInNanoseconds + CLOCK_DRIFT_TOLERANCE_NANOSECONDS) {
nextTick = nowNanoseconds + periodInNanoseconds;
/*
* Shift the start point back by the drift as if the whole thing
* started count periods ago.
*/
startInNanoseconds = nextTick - (periodInNanoseconds * (++count));
} else {
nextTick = startInNanoseconds + (++count * periodInNanoseconds);
}
lastNowNanoseconds = nowNanoseconds;
long delay = nextTick - nowNanoseconds;
sd.replace(schedule(this, delay, TimeUnit.NANOSECONDS));
}
}
}
}
static class PeriodicDirectTask
implements Runnable, Disposable {
final Runnable run;
@NonNull
final Worker worker;
@NonNull
volatile boolean disposed;
PeriodicDirectTask(@NonNull Runnable run, @NonNull Worker worker) {
this.run = run;
this.worker = worker;
}
@Override
public void run() {
if (!disposed) {
try {
run.run();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
worker.dispose();
throw ExceptionHelper.wrapOrThrow(ex);
}
}
}
@Override
public void dispose() {
disposed = true;
worker.dispose();
}
@Override
public boolean isDisposed() {
return disposed;
}
}
static final class DisposeTask implements Runnable, Disposable {
final Runnable decoratedRun;
final Worker w;
Thread runner;
DisposeTask(Runnable decoratedRun, Worker w) {
this.decoratedRun = decoratedRun;
this.w = w;
}
@Override
public void run() {
runner = Thread.currentThread();
try {
decoratedRun.run();
} finally {
dispose();
runner = null;
}
}
@Override
public void dispose() {
if (runner == Thread.currentThread() && w instanceof NewThreadWorker) {
((NewThreadWorker)w).shutdown();
} else {
w.dispose();
}
}
@Override
public boolean isDisposed() {
return w.isDisposed();
}
}
}
a Scheduler and a Subscription
* @param combine the function that takes a two-level nested Flowable sequence of a Completable and returns
* the Completable that will be subscribed to and should trigger the execution of the scheduled Actions.
* @return the Scheduler with the customized execution behavior
* @since 2.1
*/
@SuppressWarnings("unchecked")
@NonNull
public S when(@NonNull Function