/** Wipes out all the items currently in the queue, as if all of them are cancelled at once. */
public synchronized void clear() {
for (WaitingItem i : waitingList) i.onCancelled();
waitingList.clear();
blockedProjects.cancelAll();
buildables.cancelAll();
scheduleMaintenance();
}
/**
* Called by the executor to fetch something to build next.
*
* <p>This method blocks until a next project becomes buildable.
*/
public Queue.Item pop() throws InterruptedException {
final Executor exec = Executor.currentExecutor();
try {
while (true) {
final JobOffer offer = new JobOffer(exec);
long sleep = -1;
synchronized (this) {
// consider myself parked
assert !parked.containsKey(exec);
parked.put(exec, offer);
// reuse executor thread to do a queue maintenance.
// at the end of this we get all the buildable jobs
// in the buildables field.
maintain();
// allocate buildable jobs to executors
Iterator<BuildableItem> itr = buildables.iterator();
while (itr.hasNext()) {
BuildableItem p = itr.next();
// one last check to make sure this build is not blocked.
if (isBuildBlocked(p.task)) {
itr.remove();
blockedProjects.put(p.task, new BlockedItem(p));
continue;
}
JobOffer runner = loadBalancer.choose(p.task, new ApplicableJobOfferList(p.task));
if (runner == null)
// if we couldn't find the executor that fits,
// just leave it in the buildables list and
// check if we can execute other projects
continue;
assert runner.canTake(p.task);
// found a matching executor. use it.
runner.set(p);
itr.remove();
}
// we went over all the buildable projects and awaken
// all the executors that got work to do. now, go to sleep
// until this thread is awakened. If this executor assigned a job to
// itself above, the block method will return immediately.
if (!waitingList.isEmpty()) {
// wait until the first item in the queue is due
sleep = peek().timestamp.getTimeInMillis() - new GregorianCalendar().getTimeInMillis();
if (sleep < 100) sleep = 100; // avoid wait(0)
}
}
// this needs to be done outside synchronized block,
// so that executors can maintain a queue while others are sleeping
if (sleep == -1) offer.event.block();
else offer.event.block(sleep);
synchronized (this) {
// retract the offer object
assert parked.get(exec) == offer;
parked.remove(exec);
// am I woken up because I have a project to build?
if (offer.item != null) {
// if so, just build it
LOGGER.fine("Pop returning " + offer.item + " for " + exec.getName());
offer.item.future.startExecuting(exec);
return offer.item;
}
// otherwise run a queue maintenance
}
}
} finally {
synchronized (this) {
// remove myself from the parked list
JobOffer offer = parked.remove(exec);
if (offer != null && offer.item != null) {
// we are already assigned a project,
// ask for someone else to build it.
// note that while this thread is waiting for CPU
// someone else can schedule this build again,
// so check the contains method first.
if (!contains(offer.item.task)) buildables.put(offer.item.task, offer.item);
}
// since this executor might have been chosen for
// maintenance, schedule another one. Worst case
// we'll just run a pointless maintenance, and that's
// fine.
scheduleMaintenance();
}
}
}
/**
* Schedules an execution of a task.
*
* @since 1.311
* @return null if this task is already in the queue and therefore the add operation was no-op.
* Otherwise indicates the {@link WaitingItem} object added, although the nature of the queue
* is that such {@link Item} only captures the state of the item at a particular moment, and
* by the time you inspect the object, some of its information can be already stale.
* <p>That said, one can still look at {@link WaitingItem#future}, {@link WaitingItem#id},
* etc.
*/
private synchronized WaitingItem scheduleInternal(Task p, int quietPeriod, List<Action> actions) {
WaitingItem added = null;
List<Item> items = getItems(p);
Calendar due = new GregorianCalendar();
due.add(Calendar.SECOND, quietPeriod);
List<Item> duplicatesInQueue = new ArrayList<Item>();
for (Item item : items) {
boolean shouldScheduleItem = false;
for (Action action : item.getActions()) {
if (action instanceof QueueAction)
shouldScheduleItem |= ((QueueAction) action).shouldSchedule(actions);
}
for (Action action : actions) {
if (action instanceof QueueAction) {
shouldScheduleItem |= ((QueueAction) action).shouldSchedule(item.getActions());
}
}
if (!shouldScheduleItem) {
duplicatesInQueue.add(item);
}
}
if (duplicatesInQueue.size() == 0) {
LOGGER.fine(p.getFullDisplayName() + " added to queue");
// put the item in the queue
waitingList.add(added = new WaitingItem(due, p, actions));
} else {
// the requested build is already queued, so will not be added
List<WaitingItem> waitingDuplicates = new ArrayList<WaitingItem>();
for (Item item : duplicatesInQueue) {
for (Action a : actions) {
if (a instanceof FoldableAction) {
((FoldableAction) a).foldIntoExisting(item.task, item.getActions());
}
}
if ((item instanceof WaitingItem)) waitingDuplicates.add((WaitingItem) item);
}
if (duplicatesInQueue.size() == 0) {
// all duplicates in the queue are already in the blocked or
// buildable stage no need to requeue
return null;
}
// TODO: avoid calling scheduleMaintenance() if none of the waiting items
// actually change
for (WaitingItem wi : waitingDuplicates) {
if (quietPeriod <= 0) {
// the user really wants to build now, and they mean NOW.
// so let's pull in the timestamp if we can.
if (wi.timestamp.before(due)) continue;
} else {
// otherwise we do the normal quiet period implementation
if (wi.timestamp.after(due)) continue;
// quiet period timer reset. start the period over again
}
// waitingList is sorted, so when we change a timestamp we need to maintain order
waitingList.remove(wi);
wi.timestamp = due;
waitingList.add(wi);
}
}
scheduleMaintenance(); // let an executor know that a new item is in the queue.
return added;
}