/**
* Removes any tasks waiting to be run. Will not interrupt any tasks currently running if {@link
* #tick(ExceptionHandlerInterface)} is being called. But will avoid additional tasks from being
* run on the current {@link #tick(ExceptionHandlerInterface)} call.
*
* <p>If tasks are added concurrently during this invocation they may or may not be removed.
*
* @return List of runnables which were waiting in the task queue to be executed (and were now
* removed)
*/
public List<Runnable> clearTasks() {
List<TaskContainer> containers;
synchronized (scheduledQueue.getModificationLock()) {
containers = new ArrayList<TaskContainer>(executeQueue.size() + scheduledQueue.size());
Iterator<? extends TaskContainer> it = executeQueue.iterator();
while (it.hasNext()) {
TaskContainer tc = it.next();
/* we must use executeQueue.remove(Object) instead of it.remove()
* This is to assure it is atomically removed (without executing)
*/
if (!tc.running && executeQueue.remove(tc)) {
int index = ListUtils.getInsertionEndIndex(containers, tc, true);
containers.add(index, tc);
}
}
it = scheduledQueue.iterator();
while (it.hasNext()) {
TaskContainer tc = it.next();
if (!tc.running) {
int index = ListUtils.getInsertionEndIndex(containers, tc, true);
containers.add(index, tc);
}
}
scheduledQueue.clear();
}
return ContainerHelper.getContainedRunnables(containers);
}
/**
* Checks if there are tasks ready to be run on the scheduler. Generally this is called from the
* same thread that would call {@link #tick(ExceptionHandlerInterface)} (but does not have to be).
* If {@link #tick(ExceptionHandlerInterface)} is not currently being called, this call indicates
* if the next {@link #tick(ExceptionHandlerInterface)} will have at least one task to run. If
* {@link #tick(ExceptionHandlerInterface)} is currently being invoked, this call will do a best
* attempt to indicate if there is at least one more task to run (not including the task which may
* currently be running). It's a best attempt as it will try not to block the thread invoking
* {@link #tick(ExceptionHandlerInterface)} to prevent it from accepting additional work.
*
* @return {@code true} if there are task waiting to run
*/
public boolean hasTaskReadyToRun() {
while (true) {
TaskContainer nextExecuteTask = executeQueue.peek();
if (nextExecuteTask != null) {
if (nextExecuteTask.running) {
// loop and retry, should be removed from queue shortly
Thread.yield();
} else {
return true;
}
} else {
break;
}
}
synchronized (scheduledQueue.getModificationLock()) {
Iterator<TaskContainer> it = scheduledQueue.iterator();
while (it.hasNext()) {
TaskContainer scheduledTask = it.next();
if (scheduledTask.running) {
continue;
} else if (scheduledTask.getDelayInMillis() <= 0) {
return true;
} else {
return false;
}
}
}
return false;
}
/**
* Adds a task to scheduled/recurring queue. This call is more expensive than {@link
* #addImmediateExecute(OneTimeTask)}, but is necessary for any tasks which are either delayed or
* recurring.
*
* @param runnable Task to execute on next {@link #tick(ExceptionHandlerInterface)} call
*/
protected void addScheduled(TaskContainer runnable) {
synchronized (scheduledQueue.getModificationLock()) {
ClockWrapper.stopForcingUpdate();
try {
int insertionIndex = ListUtils.getInsertionEndIndex(scheduledQueue, runnable, true);
scheduledQueue.add(insertionIndex, runnable);
} finally {
ClockWrapper.resumeForcingUpdate();
}
}
notifyQueueUpdate();
}
/**
* Call to get the next task that is ready to be run. If there are no tasks, or the next task
* still has a remaining delay, this will return {@code null}.
*
* <p>If this is being called in parallel with a {@link #tick(ExecutionHandlerInterface)} call,
* the returned task may already be running. You must check the {@code TaskContainer.running}
* boolean if this condition is important to you.
*
* @param onlyReturnReadyTask {@code false} to return scheduled tasks which may not be ready for
* execution
* @return next ready task, or {@code null} if there are none
*/
protected TaskContainer getNextTask(boolean onlyReturnReadyTask) {
TaskContainer nextScheduledTask = scheduledQueue.peekFirst();
TaskContainer nextExecuteTask = executeQueue.peek();
if (nextExecuteTask != null) {
if (nextScheduledTask != null) {
long scheduleDelay;
long executeDelay;
ClockWrapper.stopForcingUpdate();
try {
scheduleDelay = nextScheduledTask.getDelayInMillis();
executeDelay = nextExecuteTask.getDelayInMillis();
} finally {
ClockWrapper.resumeForcingUpdate();
}
if (scheduleDelay < executeDelay) {
return nextScheduledTask;
} else {
return nextExecuteTask;
}
} else {
return nextExecuteTask;
}
} else if (!onlyReturnReadyTask
|| (nextScheduledTask != null && nextScheduledTask.getDelayInMillis() <= 0)) {
return nextScheduledTask;
} else {
return null;
}
}
@Override
public boolean remove(Callable<?> task) {
if (ContainerHelper.remove(executeQueue, task)) {
return true;
}
synchronized (scheduledQueue.getModificationLock()) {
return ContainerHelper.remove(scheduledQueue, task);
}
}
