@Test
public void timedTaskHandlerAccepts() {
ScheduledTask task =
new ScheduledTask(
testRunnable,
new DummyTaskOwner(),
Priority.getDefaultPriority(),
System.currentTimeMillis() + TimedTaskHandler.FUTURE_THRESHOLD + 50);
assertTrue((new TimedTaskHandler(new TimedTaskConsumerImpl())).runDelayed(task));
}
/** Tests for the utility structures shared between schedulers. */
@RunWith(NameRunner.class)
public class TestInternalStructuresImpl {
//
private static final ApplicationScheduler scheduler = new DummyApplicationScheduler();
// a basic KernelRunnable that does nothing
private static final KernelRunnable testRunnable = new DummyKernelRunnable();
// a basic task that shouldn't be run but can be used for tests
private static final ScheduledTask testTask =
new ScheduledTask(testRunnable, new DummyTaskOwner(), Priority.getDefaultPriority(), 0);
// a basic, recurring task that shouldn't be run but can be used for tests
private static final ScheduledTask recurringTestTask =
new ScheduledTask(testRunnable, new DummyTaskOwner(), Priority.getDefaultPriority(), 0, 100);
public TestInternalStructuresImpl() {}
@Before
public void setupSingleTest() {
// setup for each individual test can happen here
}
@After
public void teardownSingleTest() {
// teardown for each individual test can happen here
}
/**
* RecurringTaskHandleImpl tests.
*
* <p>Note that there are no start/cancel tests here because they are already done in the
* ApplicationScheduler tests, where this class' interface is exposed and it must be tested since
* we don't know what implementation a given scheduler will choose to use.
*/
@Test
public void constructRecurringHandle() throws Exception {
new RecurringTaskHandleImpl(scheduler, recurringTestTask);
}
@Test(expected = NullPointerException.class)
public void constructRecurringHandleNullScheduler() throws Exception {
new RecurringTaskHandleImpl(null, recurringTestTask);
}
@Test(expected = NullPointerException.class)
public void constructRecurringHandleNullTask() throws Exception {
new RecurringTaskHandleImpl(scheduler, null);
}
@Test(expected = IllegalArgumentException.class)
public void constructRecurringHandleNonRecurringTask() throws Exception {
new RecurringTaskHandleImpl(scheduler, testTask);
}
@Test
public void scheduleNextRecurrence() throws Exception {
RecurringTaskHandleImpl handle = new RecurringTaskHandleImpl(scheduler, recurringTestTask);
handle.scheduleNextRecurrence();
}
@Test(expected = NullPointerException.class)
public void setTimerTaskNull() throws Exception {
RecurringTaskHandleImpl handle = new RecurringTaskHandleImpl(scheduler, recurringTestTask);
handle.setTimerTask(null);
}
/** ScheduledTask tests. */
@Test
public void constructScheduledTaskFromScheduledTask() {
new ScheduledTask(recurringTestTask, 0);
}
@Test(expected = NullPointerException.class)
public void constructScheduledTaskNullScheduledTask() throws Exception {
new ScheduledTask(null, 0);
}
@Test(expected = NullPointerException.class)
public void constructScheduledTaskNullTask() throws Exception {
new ScheduledTask(null, new DummyTaskOwner(), Priority.getDefaultPriority(), 0);
}
@Test(expected = NullPointerException.class)
public void constructScheduledTaskNullOwner() throws Exception {
new ScheduledTask(testRunnable, null, Priority.getDefaultPriority(), 0);
}
@Test(expected = NullPointerException.class)
public void constructScheduledTaskNullPriority() throws Exception {
new ScheduledTask(testRunnable, new DummyTaskOwner(), null, 0);
}
@Test
public void assertIsRecurring() {
assertTrue(recurringTestTask.isRecurring());
}
@Test
public void assertIsNotRecurring() {
assertFalse(testTask.isRecurring());
}
@Test
public void assertIsStillRecurring() {
assertTrue((new ScheduledTask(recurringTestTask, 10)).isRecurring());
}
@Test
public void setRecurringHandleNonRecurringTask() {
RecurringTaskHandleImpl handle = new RecurringTaskHandleImpl(scheduler, recurringTestTask);
assertFalse(testTask.setRecurringTaskHandle(handle));
}
@Test
public void setRecurringHandleOnceOnly() {
RecurringTaskHandleImpl handle = new RecurringTaskHandleImpl(scheduler, recurringTestTask);
assertTrue(recurringTestTask.setRecurringTaskHandle(handle));
assertFalse(recurringTestTask.setRecurringTaskHandle(handle));
}
@Test
public void getRecurringHandle() {
assertNotNull(recurringTestTask.getRecurringTaskHandle());
}
/**
* SimpleTaskReservation tests.
*
* <p>Note that there are no use/cancel tests here because they are already done in the
* ApplicationScheduler tests, where this class' interface is exposed and it must be tested since
* we don't know what implementation a given scheduler will choose to use.
*/
@Test(expected = NullPointerException.class)
public void constructSimpleTaskReservationNullScheduler() throws Exception {
new SimpleTaskReservation(null, testTask);
}
@Test(expected = NullPointerException.class)
public void constructSimpleTaskReservationNullTask() throws Exception {
new SimpleTaskReservation(scheduler, null);
}
/** TimedTaskHandler tests. */
@Test(expected = NullPointerException.class)
public void constructTimedTaskHandleNullConsumer() throws Exception {
new TimedTaskHandler(null);
}
@Test
public void timedTaskHandlerRejects() {
assertFalse((new TimedTaskHandler(new TimedTaskConsumerImpl())).runDelayed(testTask));
}
@Test
public void timedTaskHandlerAccepts() {
ScheduledTask task =
new ScheduledTask(
testRunnable,
new DummyTaskOwner(),
Priority.getDefaultPriority(),
System.currentTimeMillis() + TimedTaskHandler.FUTURE_THRESHOLD + 50);
assertTrue((new TimedTaskHandler(new TimedTaskConsumerImpl())).runDelayed(task));
}
/** Utility classes. */
private static class DummyApplicationScheduler implements ApplicationScheduler {
public int getReadyCount() {
return 0;
}
public ScheduledTask getNextTask(boolean wait) throws InterruptedException {
return null;
}
public int getNextTasks(Collection<ScheduledTask> tasks, int max) {
return 0;
}
public TaskReservation reserveTask(ScheduledTask task) {
return new SimpleTaskReservation(this, task);
}
public void addTask(ScheduledTask task) {}
public RecurringTaskHandle addRecurringTask(ScheduledTask task) {
return new RecurringTaskHandleImpl(this, task);
}
public void notifyCancelled(ScheduledTask task) {}
public void shutdown() {}
}
private static class TimedTaskConsumerImpl implements TimedTaskConsumer {
public void timedTaskReady(ScheduledTask task) {}
}
/** Adapter to let JUnit4 tests run in a JUnit3 execution environment. */
public static junit.framework.Test suite() {
return new JUnit4TestAdapter(TestInternalStructuresImpl.class);
}
}
@Test(expected = NullPointerException.class)
public void constructScheduledTaskNullTask() throws Exception {
new ScheduledTask(null, new DummyTaskOwner(), Priority.getDefaultPriority(), 0);
}
@Test(expected = NullPointerException.class)
public void constructScheduledTaskNullOwner() throws Exception {
new ScheduledTask(testRunnable, null, Priority.getDefaultPriority(), 0);
}
/**
* Package-private implementation of {@code TransactionScheduler} that is used by the system for
* scheduling and running all transactional tasks.
*/
final class TransactionSchedulerImpl
implements TransactionScheduler, PriorityScheduler, ProfileListener {
// logger for this class
private static final LoggerWrapper logger =
new LoggerWrapper(Logger.getLogger(TransactionSchedulerImpl.class.getName()));
/** The property used to define which queue implementation should back this scheduler. */
public static final String SCHEDULER_QUEUE_PROPERTY = "com.sun.sgs.impl.kernel.scheduler.queue";
// the default scheduler
private static final String DEFAULT_SCHEDULER_QUEUE =
"com.sun.sgs.impl.kernel.schedule.FIFOSchedulerQueue";
/** The property used to define the default number of initial consumer threads. */
public static final String CONSUMER_THREADS_PROPERTY =
"com.sun.sgs.impl.kernel.transaction.threads";
// the default number of initial consumer threads
private static final String DEFAULT_CONSUMER_THREADS = "4";
// the default priority for tasks
private static final Priority defaultPriority = Priority.getDefaultPriority();
// the coordinator used to create and coordinate transactions
private final TransactionCoordinator transactionCoordinator;
// the backing scheduler queue used for ordering tasks
private final SchedulerQueue backingQueue;
// the collector handle used for profiling data
private final ProfileCollectorHandle profileCollectorHandle;
// the coordinator for all transactional object access
private final AccessCoordinatorHandle accessCoordinator;
// the executor service used to manage our threads
private final ExecutorService executor;
// the actual number of threads we're currently using
private final AtomicInteger threadCount = new AtomicInteger(0);
// flag to note that this scheduler has shutdown
private volatile boolean isShutdown = false;
// the context we're using for the application's tasks
private volatile KernelContext kernelContext = null;
// the number of dependent tasks sitting in queues
private final AtomicInteger dependencyCount = new AtomicInteger(0);
/**
* Creates an instance of {@code TransactionSchedulerImpl}.
*
* @param properties the {@code Properties} for the system
* @param transactionCoordinator the {@code TransactionCoordinator} used by the system to manage
* transactions
* @param profileCollectorHandle the {@code ProfileCollectorHandler} used to manage collection of
* per-task profiling data
* @param accessCoordinator the {@code AccessCoordinator} used by the system to managed shared
* data
* @throws InvocationTargetException if there is a failure initializing the {@code SchedulerQueue}
* @throws Exception if there is any failure creating the scheduler
*/
TransactionSchedulerImpl(
Properties properties,
TransactionCoordinator transactionCoordinator,
ProfileCollectorHandle profileCollectorHandle,
AccessCoordinatorHandle accessCoordinator)
throws Exception {
logger.log(Level.CONFIG, "Creating a Transaction Scheduler");
if (properties == null) {
throw new NullPointerException("Properties cannot be null");
}
if (transactionCoordinator == null) {
throw new NullPointerException("Coordinator cannot be null");
}
if (profileCollectorHandle == null) {
throw new NullPointerException("Collector handle cannot be null");
}
if (accessCoordinator == null) {
throw new NullPointerException("AccessCoordinator cannot be null");
}
this.transactionCoordinator = transactionCoordinator;
this.profileCollectorHandle = profileCollectorHandle;
this.accessCoordinator = accessCoordinator;
String queueName = properties.getProperty(SCHEDULER_QUEUE_PROPERTY, DEFAULT_SCHEDULER_QUEUE);
try {
Class<?> queueClass = Class.forName(queueName);
Constructor<?> queueCtor = queueClass.getConstructor(Properties.class);
this.backingQueue = (SchedulerQueue) (queueCtor.newInstance(properties));
} catch (InvocationTargetException e) {
if (logger.isLoggable(Level.CONFIG)) {
logger.logThrow(
Level.CONFIG, e.getCause(), "Queue {0} " + "failed to initialize", queueName);
}
throw e;
} catch (Exception e) {
if (logger.isLoggable(Level.CONFIG)) {
logger.logThrow(Level.CONFIG, e, "Queue {0} unavailable", queueName);
}
throw e;
}
// startup the requested number of consumer threads
// NOTE: this is a simple implmentation to replicate the previous
// behvavior, with the assumption that it will change if the
// scheduler starts trying to add or drop consumers adaptively
int requestedThreads =
Integer.parseInt(
properties.getProperty(CONSUMER_THREADS_PROPERTY, DEFAULT_CONSUMER_THREADS));
if (logger.isLoggable(Level.CONFIG)) {
logger.log(Level.CONFIG, "Using {0} transaction consumer threads", requestedThreads);
}
this.executor = Executors.newCachedThreadPool();
for (int i = 0; i < requestedThreads; i++) {
executor.submit(new TaskConsumer());
}
}
/**
* Package-private method used to set the context being used by the kernel.
*
* @param kernelContext the {@code KernelContext} for this scheduler
*/
void setContext(KernelContext kernelContext) {
this.kernelContext = kernelContext;
}
/*
* Implementations of the TransactionScheduler interface.
*/
/** {@inheritDoc} */
public TaskReservation reserveTask(KernelRunnable task, Identity owner) {
ScheduledTaskImpl t =
new ScheduledTaskImpl(task, owner, defaultPriority, System.currentTimeMillis());
return backingQueue.reserveTask(t);
}
/** {@inheritDoc} */
public TaskReservation reserveTask(KernelRunnable task, Identity owner, long startTime) {
ScheduledTaskImpl t = new ScheduledTaskImpl(task, owner, defaultPriority, startTime);
return backingQueue.reserveTask(t);
}
/** {@inheritDoc} */
public void scheduleTask(KernelRunnable task, Identity owner) {
backingQueue.addTask(
new ScheduledTaskImpl(task, owner, defaultPriority, System.currentTimeMillis()));
}
/** {@inheritDoc} */
public void scheduleTask(KernelRunnable task, Identity owner, long startTime) {
backingQueue.addTask(new ScheduledTaskImpl(task, owner, defaultPriority, startTime));
}
/** {@inheritDoc} */
public RecurringTaskHandle scheduleRecurringTask(
KernelRunnable task, Identity owner, long startTime, long period) {
ScheduledTaskImpl scheduledTask =
new ScheduledTaskImpl(task, owner, defaultPriority, startTime, period);
RecurringTaskHandle handle = backingQueue.createRecurringTaskHandle(scheduledTask);
scheduledTask.setRecurringTaskHandle(handle);
return handle;
}
/** {@inheritDoc} */
public TaskQueue createTaskQueue() {
if (isShutdown) {
throw new IllegalStateException("Scheduler is shutdown");
}
return new TaskQueueImpl();
}
/** {@inheritDoc} */
public void runTask(KernelRunnable task, Identity owner) throws Exception {
if (isShutdown) {
throw new IllegalStateException("Scheduler is shutdown");
}
if (ContextResolver.isCurrentTransaction()) {
// we're already active in a transaction, so just run the task
task.run();
} else {
// we're starting a new transaction
ScheduledTaskImpl scheduledTask =
new ScheduledTaskImpl(task, owner, defaultPriority, System.currentTimeMillis());
waitForTask(scheduledTask, false);
}
}
/*
* Implementations of the PriorityScheduler interface.
*/
/** {@inheritDoc} */
public TaskReservation reserveTask(KernelRunnable task, Identity owner, Priority priority) {
ScheduledTaskImpl t = new ScheduledTaskImpl(task, owner, priority, System.currentTimeMillis());
return backingQueue.reserveTask(t);
}
/** {@inheritDoc} */
public void scheduleTask(KernelRunnable task, Identity owner, Priority priority) {
backingQueue.addTask(new ScheduledTaskImpl(task, owner, priority, System.currentTimeMillis()));
}
/*
* Implementations for the ProfileListener interface.
*/
/** {@inheritDoc} */
public void propertyChange(PropertyChangeEvent event) {
// see comment in notifyThreadLeaving
}
/** {@inheritDoc} */
public void report(ProfileReport profileReport) {
// see comment in notifyThreadLeaving
}
/** {@inheritDoc} */
public void shutdown() {
synchronized (this) {
if (isShutdown) {
return; // return silently
}
isShutdown = true;
executor.shutdownNow();
backingQueue.shutdown();
}
}
/*
* Utility methods and classes.
*/
/**
* Private method that blocks until the task has completed, re-throwing any exception resulting
* from the task failing.
*/
private void waitForTask(ScheduledTaskImpl task, boolean unbounded) throws Exception {
Throwable t = null;
try {
// NOTE: calling executeTask() directly means that we're trying
// to run the transaction in the calling thread, so there are
// actually more threads running tasks simulaneously than there
// are threads in the scheduler pool. This could be changed to
// hand-off the task and wait for the result if we wanted more
// direct control over concurrent transactions
executeTask(task, unbounded, false);
// wait for the task to complete...at this point it may have
// already completed, or else it is being re-tried in a
// scheduler thread
t = task.get();
} catch (InterruptedException ie) {
// we were interrupted, so try to cancel the task, re-throwing
// the interruption if that succeeds or looking at the result
// if the task completes before it can be cancelled
if (task.cancel(false)) {
backingQueue.notifyCancelled(task);
throw ie;
}
if (task.isCancelled()) {
throw ie;
}
t = task.get();
}
// if the result of the task was a permananent failure, then
// re-throw the exception
if (t != null) {
if (t instanceof Exception) {
throw (Exception) t;
}
throw (Error) t;
}
}
/**
* Package-private method that runs the given task in a transaction that is not bound by any
* timeout value (i.e., is bound only by the {@code com.sun.sgs.txn.timeout.unbounded} property
* value).
*
* @param task the {@code KernelRunnable} to run transactionally
* @param owner the {@code Identity} that owns the task
* @throws IllegalStateException if this method is called from an actively running transaction
* @throws Exception if there is any failure that does not result in re-trying the task
*/
void runUnboundedTask(KernelRunnable task, Identity owner) throws Exception {
if (isShutdown) {
throw new IllegalStateException("Scheduler is shutdown");
}
if (ContextResolver.isCurrentTransaction()) {
throw new IllegalStateException("Cannot be called from within " + "an active transaction");
}
// NOTE: in the current system we only use this method once, and
// that's when the application is initialized, in which case there
// is no other task trying to run...if we decide to start using
// this method more broadly, then it should probably use a separate
// thread-pool so that it doesn't affect transaction latency
ScheduledTaskImpl scheduledTask =
new ScheduledTaskImpl(task, owner, defaultPriority, System.currentTimeMillis());
waitForTask(scheduledTask, true);
}
/**
* Notifies the scheduler that a thread has been started to consume tasks as they become ready.
*/
private void notifyThreadJoining() {
profileCollectorHandle.notifyThreadAdded();
threadCount.incrementAndGet();
}
/** Notifies the scheduler that a thread has been interrupted and is finishing its work. */
private void notifyThreadLeaving() {
profileCollectorHandle.notifyThreadRemoved();
// NOTE: we're not yet trying to adapt the number of threads being
// used, so we assume that threads are only lost when the system
// wants to shutdown...in practice, this should look at some
// threshold and see if another consumer needs to be created
if (threadCount.decrementAndGet() == 0) {
logger.log(Level.CONFIG, "No more threads are consuming tasks");
shutdown();
}
}
/**
* Private {@code Runnable} used to consume tasks as they become available from the {@code
* SchedulerQueue}. Once started, it will continue running until it catches an {@code
* InterruptedException}.
*/
private class TaskConsumer implements Runnable {
/** {@inheritDoc} */
public void run() {
logger.log(Level.FINE, "Starting a consumer for transactions");
notifyThreadJoining();
try {
while (true) {
// wait for the next task, at which point we may get
// interrupted and should therefore return
ScheduledTaskImpl task = (ScheduledTaskImpl) (backingQueue.getNextTask(true));
// run the task, checking if it completed
if (executeTask(task, false, true)) {
// if it's a recurring task, schedule the next run
if (task.isRecurring()) {
long nextStart = task.getStartTime() + task.getPeriod();
task = new ScheduledTaskImpl(task, nextStart);
backingQueue.addTask(task);
}
// if it has dependent tasks, schedule the next one
TaskQueueImpl queue = (TaskQueueImpl) (task.getTaskQueue());
if (queue != null) {
queue.scheduleNextTask();
}
}
}
} catch (InterruptedException ie) {
if (logger.isLoggable(Level.FINE)) {
logger.logThrow(Level.FINE, ie, "Consumer is finishing");
}
} catch (Exception e) {
// this should never happen, since running the task should
// never throw an exception that isn't handled
logger.logThrow(Level.SEVERE, e, "Fatal error for consumer");
} finally {
notifyThreadLeaving();
}
}
}
/**
* Private method that executes a single task, creating the transaction state and handling re-try
* as appropriate. If the thread calling this method is interrupted before the task can complete
* then this method attempts to re-schedule the task to run in another thread if {@code
* retryOnInterruption} is {@code true} and always re-throws the associated {@code
* InterruptedException}. Providing {@code true} for the {@code unbounded} parameter results in a
* transaction with timeout value as specified by the value of the {@code
* TransactionCoordinator.TXN_UNBOUNDED_TIMEOUT_PROPERTY} property.
*
* <p>This method returns {@code true} if the task was completed or failed permanently, and {@code
* false} otherwise. If {@code false} is returned then the task is scheduled to be re-tried at
* some point in the future, possibly by another thread, by this method. The caller may query the
* status of the task and wait for the task to complete or fail permanently through the {@code
* ScheduledTaskImpl} interface.
*/
private boolean executeTask(
ScheduledTaskImpl task, boolean unbounded, boolean retryOnInterruption)
throws InterruptedException {
logger.log(Level.FINEST, "starting a new transactional task");
// store the current owner, and then push the new thread detail
Identity parent = ContextResolver.getCurrentOwner();
ContextResolver.setTaskState(kernelContext, task.getOwner());
try {
// keep trying to run the task until we succeed, tracking how
// many tries it actually took
while (true) {
if (!task.setRunning(true)) {
// this task is already finished
return true;
}
// NOTE: We could report the two queue sizes separately,
// so we should figure out how we want to represent these
int waitSize = backingQueue.getReadyCount() + dependencyCount.get();
profileCollectorHandle.startTask(
task.getTask(), task.getOwner(), task.getStartTime(), waitSize);
task.incrementTryCount();
Transaction transaction = null;
try {
// setup the transaction state
TransactionHandle handle = transactionCoordinator.createTransaction(unbounded);
transaction = handle.getTransaction();
ContextResolver.setCurrentTransaction(transaction);
try {
// notify the profiler and access coordinator
profileCollectorHandle.noteTransactional(transaction.getId());
accessCoordinator.notifyNewTransaction(
transaction, task.getStartTime(), task.getTryCount());
// run the task in the new transactional context
task.getTask().run();
} finally {
// regardless of the outcome, always clear the current
// transaction state before proceeding...
ContextResolver.clearCurrentTransaction(transaction);
}
// try to commit the transaction...note that there's the
// chance that the application code masked the orginal
// cause of a failure, so we'll check for that first,
// re-throwing the root cause in that case
if (transaction.isAborted()) {
throw transaction.getAbortCause();
}
handle.commit();
// the task completed successfully, so we're done
profileCollectorHandle.finishTask(task.getTryCount());
task.setDone(null);
return true;
} catch (InterruptedException ie) {
// make sure the transaction was aborted
if (!transaction.isAborted()) {
transaction.abort(ie);
}
profileCollectorHandle.finishTask(task.getTryCount(), ie);
// if the task didn't finish because of the interruption
// then we want to note that and possibly re-queue the
// task to run in a usable thread
if (task.setInterrupted() && retryOnInterruption) {
if (!handoffRetry(task, ie)) {
// if the task couldn't be re-queued, then there's
// nothing left to do but drop it
task.setDone(ie);
if (logger.isLoggable(Level.WARNING)) {
logger.logThrow(Level.WARNING, ie, "dropping " + "an interrupted task: {0}" + task);
}
}
}
// always re-throw the interruption
throw ie;
} catch (Throwable t) {
// make sure the transaction was aborted
if ((transaction != null) && (!transaction.isAborted())) {
transaction.abort(t);
}
profileCollectorHandle.finishTask(task.getTryCount(), t);
// some error occurred, so see if we should re-try
if (!shouldRetry(task, t)) {
// the task is not being re-tried
task.setDone(t);
return true;
} else {
// see if the re-try should be handed-off
task.setRunning(false);
if (handoffRetry(task, t)) {
return false;
}
}
}
}
} finally {
// always restore the previous owner before leaving...
ContextResolver.setTaskState(kernelContext, parent);
}
}
/**
* Private method that determines whether a given task should be re-tried based on the given
* {@code Throwable} that caused failure. If this returns {@code true} then the task should be
* re-tried. Otherwise, the task should be dropped.
*/
private boolean shouldRetry(ScheduledTaskImpl task, Throwable t) {
// NOTE: as a first-pass implementation this simply instructs the
// caller to try again if retry is requested, but other strategies
// (like the number of times re-tried) might be considered later
if ((t instanceof ExceptionRetryStatus) && (((ExceptionRetryStatus) t).shouldRetry())) {
return true;
}
// we're not re-trying the task, so log that it's being dropped
if (logger.isLoggable(Level.WARNING)) {
if (task.isRecurring()) {
logger.logThrow(
Level.WARNING,
t,
"skipping a recurrence of "
+ "a task that failed with a non-retryable "
+ "exception: {0}",
task);
} else {
logger.logThrow(
Level.WARNING,
t,
"dropping a task that " + "failed with a non-retryable exception: {0}",
task);
}
}
return false;
}
/**
* Private method that determines how to handoff a task that needs to be re-tried. If this returns
* {@code true} then the task has been taken and handed-off, and the caller is therefore no longer
* responsible for executing the task. If this returns {@code false} then it's up to the caller to
* try running the task again.
*/
private boolean handoffRetry(ScheduledTaskImpl task, Throwable t) {
// NOTE: this is a very simple initial policy that always causes
// tasks to re-try "in place" unless they were interrupted, in which
// case there's nothing to do but re-queue the task
if (t instanceof InterruptedException) {
try {
backingQueue.addTask(task);
return true;
} catch (TaskRejectedException tre) {
return false;
}
}
return false;
}
/** Private implementation of {@code TaskQueue}. */
private final class TaskQueueImpl implements TaskQueue {
private final Queue<ScheduledTaskImpl> queue = new LinkedList<ScheduledTaskImpl>();
private boolean inScheduler = false;
/** {@inheritDoc} */
public void addTask(KernelRunnable task, Identity owner) {
ScheduledTaskImpl schedTask =
new ScheduledTaskImpl(task, owner, defaultPriority, System.currentTimeMillis());
schedTask.setTaskQueue(this);
synchronized (this) {
if (inScheduler) {
dependencyCount.incrementAndGet();
queue.offer(schedTask);
} else {
inScheduler = true;
backingQueue.addTask(schedTask);
}
}
}
/** Private method to schedule the next task, if any. */
void scheduleNextTask() {
synchronized (this) {
if (queue.isEmpty()) {
inScheduler = false;
} else {
dependencyCount.decrementAndGet();
// re-set the start time before scheduling, since the
// task isn't really requested to start until all
// tasks ahead of it have run
ScheduledTaskImpl schedTask = queue.poll();
schedTask.resetStartTime();
backingQueue.addTask(schedTask);
}
}
}
}
}