1 /*
2 * Copyright 2012 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.util;
17
18 import static io.netty.util.internal.ObjectUtil.checkPositive;
19 import static io.netty.util.internal.ObjectUtil.checkNotNull;
20
21 import io.netty.util.concurrent.ImmediateExecutor;
22 import io.netty.util.internal.MathUtil;
23 import io.netty.util.internal.PlatformDependent;
24 import io.netty.util.internal.logging.InternalLogger;
25 import io.netty.util.internal.logging.InternalLoggerFactory;
26
27 import java.util.Collections;
28 import java.util.HashSet;
29 import java.util.Queue;
30 import java.util.Set;
31 import java.util.concurrent.CountDownLatch;
32 import java.util.concurrent.Executor;
33 import java.util.concurrent.Executors;
34 import java.util.concurrent.RejectedExecutionException;
35 import java.util.concurrent.ThreadFactory;
36 import java.util.concurrent.TimeUnit;
37 import java.util.concurrent.atomic.AtomicBoolean;
38 import java.util.concurrent.atomic.AtomicInteger;
39 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
40 import java.util.concurrent.atomic.AtomicLong;
41
42 import static io.netty.util.internal.StringUtil.simpleClassName;
43
44 /**
45 * A {@link Timer} optimized for approximated I/O timeout scheduling.
46 *
47 * <h3>Tick Duration</h3>
48 *
49 * As described with 'approximated', this timer does not execute the scheduled
50 * {@link TimerTask} on time. {@link HashedWheelTimer}, on every tick, will
51 * check if there are any {@link TimerTask}s behind the schedule and execute
52 * them.
53 * <p>
54 * You can increase or decrease the accuracy of the execution timing by
55 * specifying smaller or larger tick duration in the constructor. In most
56 * network applications, I/O timeout does not need to be accurate. Therefore,
57 * the default tick duration is 100 milliseconds and you will not need to try
58 * different configurations in most cases.
59 *
60 * <h3>Ticks per Wheel (Wheel Size)</h3>
61 *
62 * {@link HashedWheelTimer} maintains a data structure called 'wheel'.
63 * To put simply, a wheel is a hash table of {@link TimerTask}s whose hash
64 * function is 'dead line of the task'. The default number of ticks per wheel
65 * (i.e. the size of the wheel) is 512. You could specify a larger value
66 * if you are going to schedule a lot of timeouts.
67 *
68 * <h3>Do not create many instances.</h3>
69 *
70 * {@link HashedWheelTimer} creates a new thread whenever it is instantiated and
71 * started. Therefore, you should make sure to create only one instance and
72 * share it across your application. One of the common mistakes, that makes
73 * your application unresponsive, is to create a new instance for every connection.
74 *
75 * <h3>Implementation Details</h3>
76 *
77 * {@link HashedWheelTimer} is based on
78 * <a href="https://cseweb.ucsd.edu/users/varghese/">George Varghese</a> and
79 * Tony Lauck's paper,
80 * <a href="https://cseweb.ucsd.edu/users/varghese/PAPERS/twheel.ps.Z">'Hashed
81 * and Hierarchical Timing Wheels: data structures to efficiently implement a
82 * timer facility'</a>. More comprehensive slides are located
83 * <a href="https://www.cse.wustl.edu/~cdgill/courses/cs6874/TimingWheels.ppt">here</a>.
84 */
85 public class HashedWheelTimer implements Timer {
86
87 static final InternalLogger logger =
88 InternalLoggerFactory.getInstance(HashedWheelTimer.class);
89
90 private static final AtomicInteger INSTANCE_COUNTER = new AtomicInteger();
91 private static final AtomicBoolean WARNED_TOO_MANY_INSTANCES = new AtomicBoolean();
92 private static final int INSTANCE_COUNT_LIMIT = 64;
93 private static final long MILLISECOND_NANOS = TimeUnit.MILLISECONDS.toNanos(1);
94 private static final ResourceLeakDetector<HashedWheelTimer> leakDetector = ResourceLeakDetectorFactory.instance()
95 .newResourceLeakDetector(HashedWheelTimer.class, 1);
96
97 private static final AtomicIntegerFieldUpdater<HashedWheelTimer> WORKER_STATE_UPDATER =
98 AtomicIntegerFieldUpdater.newUpdater(HashedWheelTimer.class, "workerState");
99
100 private final ResourceLeakTracker<HashedWheelTimer> leak;
101 private final Worker worker = new Worker();
102 private final Thread workerThread;
103
104 public static final int WORKER_STATE_INIT = 0;
105 public static final int WORKER_STATE_STARTED = 1;
106 public static final int WORKER_STATE_SHUTDOWN = 2;
107 @SuppressWarnings({"unused", "FieldMayBeFinal"})
108 private volatile int workerState; // 0 - init, 1 - started, 2 - shut down
109
110 private final long tickDuration;
111 private final HashedWheelBucket[] wheel;
112 private final int mask;
113 private final CountDownLatch startTimeInitialized = new CountDownLatch(1);
114 private final Queue<HashedWheelTimeout> timeouts = PlatformDependent.newMpscQueue();
115 private final Queue<HashedWheelTimeout> cancelledTimeouts = PlatformDependent.newMpscQueue();
116 private final AtomicLong pendingTimeouts = new AtomicLong(0);
117 private final long maxPendingTimeouts;
118 private final Executor taskExecutor;
119
120 private volatile long startTime;
121
122 /**
123 * Creates a new timer with the default thread factory
124 * ({@link Executors#defaultThreadFactory()}), default tick duration, and
125 * default number of ticks per wheel.
126 */
127 public HashedWheelTimer() {
128 this(Executors.defaultThreadFactory());
129 }
130
131 /**
132 * Creates a new timer with the default thread factory
133 * ({@link Executors#defaultThreadFactory()}) and default number of ticks
134 * per wheel.
135 *
136 * @param tickDuration the duration between tick
137 * @param unit the time unit of the {@code tickDuration}
138 * @throws NullPointerException if {@code unit} is {@code null}
139 * @throws IllegalArgumentException if {@code tickDuration} is <= 0
140 */
141 public HashedWheelTimer(long tickDuration, TimeUnit unit) {
142 this(Executors.defaultThreadFactory(), tickDuration, unit);
143 }
144
145 /**
146 * Creates a new timer with the default thread factory
147 * ({@link Executors#defaultThreadFactory()}).
148 *
149 * @param tickDuration the duration between tick
150 * @param unit the time unit of the {@code tickDuration}
151 * @param ticksPerWheel the size of the wheel
152 * @throws NullPointerException if {@code unit} is {@code null}
153 * @throws IllegalArgumentException if either of {@code tickDuration} and {@code ticksPerWheel} is <= 0
154 */
155 public HashedWheelTimer(long tickDuration, TimeUnit unit, int ticksPerWheel) {
156 this(Executors.defaultThreadFactory(), tickDuration, unit, ticksPerWheel);
157 }
158
159 /**
160 * Creates a new timer with the default tick duration and default number of
161 * ticks per wheel.
162 *
163 * @param threadFactory a {@link ThreadFactory} that creates a
164 * background {@link Thread} which is dedicated to
165 * {@link TimerTask} execution.
166 * @throws NullPointerException if {@code threadFactory} is {@code null}
167 */
168 public HashedWheelTimer(ThreadFactory threadFactory) {
169 this(threadFactory, 100, TimeUnit.MILLISECONDS);
170 }
171
172 /**
173 * Creates a new timer with the default number of ticks per wheel.
174 *
175 * @param threadFactory a {@link ThreadFactory} that creates a
176 * background {@link Thread} which is dedicated to
177 * {@link TimerTask} execution.
178 * @param tickDuration the duration between tick
179 * @param unit the time unit of the {@code tickDuration}
180 * @throws NullPointerException if either of {@code threadFactory} and {@code unit} is {@code null}
181 * @throws IllegalArgumentException if {@code tickDuration} is <= 0
182 */
183 public HashedWheelTimer(
184 ThreadFactory threadFactory, long tickDuration, TimeUnit unit) {
185 this(threadFactory, tickDuration, unit, 512);
186 }
187
188 /**
189 * Creates a new timer.
190 *
191 * @param threadFactory a {@link ThreadFactory} that creates a
192 * background {@link Thread} which is dedicated to
193 * {@link TimerTask} execution.
194 * @param tickDuration the duration between tick
195 * @param unit the time unit of the {@code tickDuration}
196 * @param ticksPerWheel the size of the wheel
197 * @throws NullPointerException if either of {@code threadFactory} and {@code unit} is {@code null}
198 * @throws IllegalArgumentException if either of {@code tickDuration} and {@code ticksPerWheel} is <= 0
199 */
200 public HashedWheelTimer(
201 ThreadFactory threadFactory,
202 long tickDuration, TimeUnit unit, int ticksPerWheel) {
203 this(threadFactory, tickDuration, unit, ticksPerWheel, true);
204 }
205
206 /**
207 * Creates a new timer.
208 *
209 * @param threadFactory a {@link ThreadFactory} that creates a
210 * background {@link Thread} which is dedicated to
211 * {@link TimerTask} execution.
212 * @param tickDuration the duration between tick
213 * @param unit the time unit of the {@code tickDuration}
214 * @param ticksPerWheel the size of the wheel
215 * @param leakDetection {@code true} if leak detection should be enabled always,
216 * if false it will only be enabled if the worker thread is not
217 * a daemon thread.
218 * @throws NullPointerException if either of {@code threadFactory} and {@code unit} is {@code null}
219 * @throws IllegalArgumentException if either of {@code tickDuration} and {@code ticksPerWheel} is <= 0
220 */
221 public HashedWheelTimer(
222 ThreadFactory threadFactory,
223 long tickDuration, TimeUnit unit, int ticksPerWheel, boolean leakDetection) {
224 this(threadFactory, tickDuration, unit, ticksPerWheel, leakDetection, -1);
225 }
226
227 /**
228 * Creates a new timer.
229 *
230 * @param threadFactory a {@link ThreadFactory} that creates a
231 * background {@link Thread} which is dedicated to
232 * {@link TimerTask} execution.
233 * @param tickDuration the duration between tick
234 * @param unit the time unit of the {@code tickDuration}
235 * @param ticksPerWheel the size of the wheel
236 * @param leakDetection {@code true} if leak detection should be enabled always,
237 * if false it will only be enabled if the worker thread is not
238 * a daemon thread.
239 * @param maxPendingTimeouts The maximum number of pending timeouts after which call to
240 * {@code newTimeout} will result in
241 * {@link java.util.concurrent.RejectedExecutionException}
242 * being thrown. No maximum pending timeouts limit is assumed if
243 * this value is 0 or negative.
244 * @throws NullPointerException if either of {@code threadFactory} and {@code unit} is {@code null}
245 * @throws IllegalArgumentException if either of {@code tickDuration} and {@code ticksPerWheel} is <= 0
246 */
247 public HashedWheelTimer(
248 ThreadFactory threadFactory,
249 long tickDuration, TimeUnit unit, int ticksPerWheel, boolean leakDetection,
250 long maxPendingTimeouts) {
251 this(threadFactory, tickDuration, unit, ticksPerWheel, leakDetection,
252 maxPendingTimeouts, ImmediateExecutor.INSTANCE);
253 }
254 /**
255 * Creates a new timer.
256 *
257 * @param threadFactory a {@link ThreadFactory} that creates a
258 * background {@link Thread} which is dedicated to
259 * {@link TimerTask} execution.
260 * @param tickDuration the duration between tick
261 * @param unit the time unit of the {@code tickDuration}
262 * @param ticksPerWheel the size of the wheel
263 * @param leakDetection {@code true} if leak detection should be enabled always,
264 * if false it will only be enabled if the worker thread is not
265 * a daemon thread.
266 * @param maxPendingTimeouts The maximum number of pending timeouts after which call to
267 * {@code newTimeout} will result in
268 * {@link java.util.concurrent.RejectedExecutionException}
269 * being thrown. No maximum pending timeouts limit is assumed if
270 * this value is 0 or negative.
271 * @param taskExecutor The {@link Executor} that is used to execute the submitted {@link TimerTask}s.
272 * The caller is responsible to shutdown the {@link Executor} once it is not needed
273 * anymore.
274 * @throws NullPointerException if either of {@code threadFactory} and {@code unit} is {@code null}
275 * @throws IllegalArgumentException if either of {@code tickDuration} and {@code ticksPerWheel} is <= 0
276 */
277 public HashedWheelTimer(
278 ThreadFactory threadFactory,
279 long tickDuration, TimeUnit unit, int ticksPerWheel, boolean leakDetection,
280 long maxPendingTimeouts, Executor taskExecutor) {
281
282 checkNotNull(threadFactory, "threadFactory");
283 checkNotNull(unit, "unit");
284 checkPositive(tickDuration, "tickDuration");
285 checkPositive(ticksPerWheel, "ticksPerWheel");
286 this.taskExecutor = checkNotNull(taskExecutor, "taskExecutor");
287
288 // Normalize ticksPerWheel to power of two and initialize the wheel.
289 wheel = createWheel(ticksPerWheel);
290 mask = wheel.length - 1;
291
292 // Convert tickDuration to nanos.
293 long duration = unit.toNanos(tickDuration);
294
295 // Prevent overflow.
296 if (duration >= Long.MAX_VALUE / wheel.length) {
297 throw new IllegalArgumentException(String.format(
298 "tickDuration: %d (expected: 0 < tickDuration in nanos < %d",
299 tickDuration, Long.MAX_VALUE / wheel.length));
300 }
301
302 if (duration < MILLISECOND_NANOS) {
303 logger.warn("Configured tickDuration {} smaller than {}, using 1ms.",
304 tickDuration, MILLISECOND_NANOS);
305 this.tickDuration = MILLISECOND_NANOS;
306 } else {
307 this.tickDuration = duration;
308 }
309
310 workerThread = threadFactory.newThread(worker);
311
312 leak = leakDetection || !workerThread.isDaemon() ? leakDetector.track(this) : null;
313
314 this.maxPendingTimeouts = maxPendingTimeouts;
315
316 if (INSTANCE_COUNTER.incrementAndGet() > INSTANCE_COUNT_LIMIT &&
317 WARNED_TOO_MANY_INSTANCES.compareAndSet(false, true)) {
318 reportTooManyInstances();
319 }
320 }
321
322 @Override
323 protected void finalize() throws Throwable {
324 try {
325 super.finalize();
326 } finally {
327 // This object is going to be GCed and it is assumed the ship has sailed to do a proper shutdown. If
328 // we have not yet shutdown then we want to make sure we decrement the active instance count.
329 if (WORKER_STATE_UPDATER.getAndSet(this, WORKER_STATE_SHUTDOWN) != WORKER_STATE_SHUTDOWN) {
330 INSTANCE_COUNTER.decrementAndGet();
331 }
332 }
333 }
334
335 private static HashedWheelBucket[] createWheel(int ticksPerWheel) {
336 ticksPerWheel = MathUtil.findNextPositivePowerOfTwo(ticksPerWheel);
337
338 HashedWheelBucket[] wheel = new HashedWheelBucket[ticksPerWheel];
339 for (int i = 0; i < wheel.length; i ++) {
340 wheel[i] = new HashedWheelBucket();
341 }
342 return wheel;
343 }
344
345 /**
346 * Starts the background thread explicitly. The background thread will
347 * start automatically on demand even if you did not call this method.
348 *
349 * @throws IllegalStateException if this timer has been
350 * {@linkplain #stop() stopped} already
351 */
352 public void start() {
353 switch (WORKER_STATE_UPDATER.get(this)) {
354 case WORKER_STATE_INIT:
355 if (WORKER_STATE_UPDATER.compareAndSet(this, WORKER_STATE_INIT, WORKER_STATE_STARTED)) {
356 workerThread.start();
357 }
358 break;
359 case WORKER_STATE_STARTED:
360 break;
361 case WORKER_STATE_SHUTDOWN:
362 throw new IllegalStateException("cannot be started once stopped");
363 default:
364 throw new Error("Invalid WorkerState");
365 }
366
367 // Wait until the startTime is initialized by the worker.
368 while (startTime == 0) {
369 try {
370 startTimeInitialized.await();
371 } catch (InterruptedException ignore) {
372 // Ignore - it will be ready very soon.
373 }
374 }
375 }
376
377 @Override
378 public Set<Timeout> stop() {
379 if (Thread.currentThread() == workerThread) {
380 throw new IllegalStateException(
381 HashedWheelTimer.class.getSimpleName() +
382 ".stop() cannot be called from " +
383 TimerTask.class.getSimpleName());
384 }
385
386 if (!WORKER_STATE_UPDATER.compareAndSet(this, WORKER_STATE_STARTED, WORKER_STATE_SHUTDOWN)) {
387 // workerState can be 0 or 2 at this moment - let it always be 2.
388 if (WORKER_STATE_UPDATER.getAndSet(this, WORKER_STATE_SHUTDOWN) != WORKER_STATE_SHUTDOWN) {
389 INSTANCE_COUNTER.decrementAndGet();
390 if (leak != null) {
391 boolean closed = leak.close(this);
392 assert closed;
393 }
394 }
395
396 return Collections.emptySet();
397 }
398
399 try {
400 boolean interrupted = false;
401 while (workerThread.isAlive()) {
402 workerThread.interrupt();
403 try {
404 workerThread.join(100);
405 } catch (InterruptedException ignored) {
406 interrupted = true;
407 }
408 }
409
410 if (interrupted) {
411 Thread.currentThread().interrupt();
412 }
413 } finally {
414 INSTANCE_COUNTER.decrementAndGet();
415 if (leak != null) {
416 boolean closed = leak.close(this);
417 assert closed;
418 }
419 }
420 Set<Timeout> unprocessed = worker.unprocessedTimeouts();
421 Set<Timeout> cancelled = new HashSet<Timeout>(unprocessed.size());
422 for (Timeout timeout : unprocessed) {
423 if (timeout.cancel()) {
424 cancelled.add(timeout);
425 }
426 }
427 return cancelled;
428 }
429
430 @Override
431 public Timeout newTimeout(TimerTask task, long delay, TimeUnit unit) {
432 checkNotNull(task, "task");
433 checkNotNull(unit, "unit");
434
435 long pendingTimeoutsCount = pendingTimeouts.incrementAndGet();
436
437 if (maxPendingTimeouts > 0 && pendingTimeoutsCount > maxPendingTimeouts) {
438 pendingTimeouts.decrementAndGet();
439 throw new RejectedExecutionException("Number of pending timeouts ("
440 + pendingTimeoutsCount + ") is greater than or equal to maximum allowed pending "
441 + "timeouts (" + maxPendingTimeouts + ")");
442 }
443
444 start();
445
446 // Add the timeout to the timeout queue which will be processed on the next tick.
447 // During processing all the queued HashedWheelTimeouts will be added to the correct HashedWheelBucket.
448 long deadline = System.nanoTime() + unit.toNanos(delay) - startTime;
449
450 // Guard against overflow.
451 if (delay > 0 && deadline < 0) {
452 deadline = Long.MAX_VALUE;
453 }
454 HashedWheelTimeout timeout = new HashedWheelTimeout(this, task, deadline);
455 timeouts.add(timeout);
456 return timeout;
457 }
458
459 /**
460 * Returns the number of pending timeouts of this {@link Timer}.
461 */
462 public long pendingTimeouts() {
463 return pendingTimeouts.get();
464 }
465
466 private static void reportTooManyInstances() {
467 if (logger.isErrorEnabled()) {
468 String resourceType = simpleClassName(HashedWheelTimer.class);
469 logger.error("You are creating too many " + resourceType + " instances. " +
470 resourceType + " is a shared resource that must be reused across the JVM, " +
471 "so that only a few instances are created.");
472 }
473 }
474
475 private final class Worker implements Runnable {
476 private final Set<Timeout> unprocessedTimeouts = new HashSet<Timeout>();
477
478 private long tick;
479
480 @Override
481 public void run() {
482 // Initialize the startTime.
483 startTime = System.nanoTime();
484 if (startTime == 0) {
485 // We use 0 as an indicator for the uninitialized value here, so make sure it's not 0 when initialized.
486 startTime = 1;
487 }
488
489 // Notify the other threads waiting for the initialization at start().
490 startTimeInitialized.countDown();
491
492 do {
493 final long deadline = waitForNextTick();
494 if (deadline > 0) {
495 int idx = (int) (tick & mask);
496 processCancelledTasks();
497 HashedWheelBucket bucket =
498 wheel[idx];
499 transferTimeoutsToBuckets();
500 bucket.expireTimeouts(deadline);
501 tick++;
502 }
503 } while (WORKER_STATE_UPDATER.get(HashedWheelTimer.this) == WORKER_STATE_STARTED);
504
505 // Fill the unprocessedTimeouts so we can return them from stop() method.
506 for (HashedWheelBucket bucket: wheel) {
507 bucket.clearTimeouts(unprocessedTimeouts);
508 }
509 for (;;) {
510 HashedWheelTimeout timeout = timeouts.poll();
511 if (timeout == null) {
512 break;
513 }
514 if (!timeout.isCancelled()) {
515 unprocessedTimeouts.add(timeout);
516 }
517 }
518 processCancelledTasks();
519 }
520
521 private void transferTimeoutsToBuckets() {
522 // transfer only max. 100000 timeouts per tick to prevent a thread to stale the workerThread when it just
523 // adds new timeouts in a loop.
524 for (int i = 0; i < 100000; i++) {
525 HashedWheelTimeout timeout = timeouts.poll();
526 if (timeout == null) {
527 // all processed
528 break;
529 }
530 if (timeout.state() == HashedWheelTimeout.ST_CANCELLED) {
531 // Was cancelled in the meantime.
532 continue;
533 }
534
535 long calculated = timeout.deadline / tickDuration;
536 timeout.remainingRounds = (calculated - tick) / wheel.length;
537
538 final long ticks = Math.max(calculated, tick); // Ensure we don't schedule for past.
539 int stopIndex = (int) (ticks & mask);
540
541 HashedWheelBucket bucket = wheel[stopIndex];
542 bucket.addTimeout(timeout);
543 }
544 }
545
546 private void processCancelledTasks() {
547 for (;;) {
548 HashedWheelTimeout timeout = cancelledTimeouts.poll();
549 if (timeout == null) {
550 // all processed
551 break;
552 }
553 try {
554 timeout.removeAfterCancellation();
555 } catch (Throwable t) {
556 if (logger.isWarnEnabled()) {
557 logger.warn("An exception was thrown while process a cancellation task", t);
558 }
559 }
560 }
561 }
562
563 /**
564 * calculate goal nanoTime from startTime and current tick number,
565 * then wait until that goal has been reached.
566 * @return Long.MIN_VALUE if received a shutdown request,
567 * current time otherwise (with Long.MIN_VALUE changed by +1)
568 */
569 private long waitForNextTick() {
570 long deadline = tickDuration * (tick + 1);
571
572 for (;;) {
573 final long currentTime = System.nanoTime() - startTime;
574 long sleepTimeMs = (deadline - currentTime + 999999) / 1000000;
575
576 if (sleepTimeMs <= 0) {
577 if (currentTime == Long.MIN_VALUE) {
578 return -Long.MAX_VALUE;
579 } else {
580 return currentTime;
581 }
582 }
583
584 // Check if we run on windows, as if thats the case we will need
585 // to round the sleepTime as workaround for a bug that only affect
586 // the JVM if it runs on windows.
587 //
588 // See https://github.com/netty/netty/issues/356
589 if (PlatformDependent.isWindows()) {
590 sleepTimeMs = sleepTimeMs / 10 * 10;
591 if (sleepTimeMs == 0) {
592 sleepTimeMs = 1;
593 }
594 }
595
596 try {
597 Thread.sleep(sleepTimeMs);
598 } catch (InterruptedException ignored) {
599 if (WORKER_STATE_UPDATER.get(HashedWheelTimer.this) == WORKER_STATE_SHUTDOWN) {
600 return Long.MIN_VALUE;
601 }
602 }
603 }
604 }
605
606 public Set<Timeout> unprocessedTimeouts() {
607 return Collections.unmodifiableSet(unprocessedTimeouts);
608 }
609 }
610
611 private static final class HashedWheelTimeout implements Timeout, Runnable {
612
613 private static final int ST_INIT = 0;
614 private static final int ST_CANCELLED = 1;
615 private static final int ST_EXPIRED = 2;
616 private static final AtomicIntegerFieldUpdater<HashedWheelTimeout> STATE_UPDATER =
617 AtomicIntegerFieldUpdater.newUpdater(HashedWheelTimeout.class, "state");
618
619 private final HashedWheelTimer timer;
620 private final TimerTask task;
621 private final long deadline;
622
623 @SuppressWarnings({"unused", "FieldMayBeFinal", "RedundantFieldInitialization" })
624 private volatile int state = ST_INIT;
625
626 // remainingRounds will be calculated and set by Worker.transferTimeoutsToBuckets() before the
627 // HashedWheelTimeout will be added to the correct HashedWheelBucket.
628 long remainingRounds;
629
630 // This will be used to chain timeouts in HashedWheelTimerBucket via a double-linked-list.
631 // As only the workerThread will act on it there is no need for synchronization / volatile.
632 HashedWheelTimeout next;
633 HashedWheelTimeout prev;
634
635 // The bucket to which the timeout was added
636 HashedWheelBucket bucket;
637
638 HashedWheelTimeout(HashedWheelTimer timer, TimerTask task, long deadline) {
639 this.timer = timer;
640 this.task = task;
641 this.deadline = deadline;
642 }
643
644 @Override
645 public Timer timer() {
646 return timer;
647 }
648
649 @Override
650 public TimerTask task() {
651 return task;
652 }
653
654 @Override
655 public boolean cancel() {
656 // only update the state it will be removed from HashedWheelBucket on next tick.
657 if (!compareAndSetState(ST_INIT, ST_CANCELLED)) {
658 return false;
659 }
660 // If a task should be canceled we put this to another queue which will be processed on each tick.
661 // So this means that we will have a GC latency of max. 1 tick duration which is good enough. This way
662 // we can make again use of our MpscLinkedQueue and so minimize the locking / overhead as much as possible.
663 timer.cancelledTimeouts.add(this);
664 return true;
665 }
666
667 private void remove() {
668 HashedWheelBucket bucket = this.bucket;
669 if (bucket != null) {
670 bucket.remove(this);
671 }
672 timer.pendingTimeouts.decrementAndGet();
673 }
674 void removeAfterCancellation() {
675 remove();
676 task.cancelled(this);
677 }
678
679 public boolean compareAndSetState(int expected, int state) {
680 return STATE_UPDATER.compareAndSet(this, expected, state);
681 }
682
683 public int state() {
684 return state;
685 }
686
687 @Override
688 public boolean isCancelled() {
689 return state() == ST_CANCELLED;
690 }
691
692 @Override
693 public boolean isExpired() {
694 return state() == ST_EXPIRED;
695 }
696
697 public void expire() {
698 if (!compareAndSetState(ST_INIT, ST_EXPIRED)) {
699 return;
700 }
701
702 try {
703 remove();
704 timer.taskExecutor.execute(this);
705 } catch (Throwable t) {
706 if (logger.isWarnEnabled()) {
707 logger.warn("An exception was thrown while submit " + TimerTask.class.getSimpleName()
708 + " for execution.", t);
709 }
710 }
711 }
712
713 @Override
714 public void run() {
715 try {
716 task.run(this);
717 } catch (Throwable t) {
718 if (logger.isWarnEnabled()) {
719 logger.warn("An exception was thrown by " + TimerTask.class.getSimpleName() + '.', t);
720 }
721 }
722 }
723
724 @Override
725 public String toString() {
726 final long currentTime = System.nanoTime();
727 long remaining = deadline - currentTime + timer.startTime;
728
729 StringBuilder buf = new StringBuilder(192)
730 .append(simpleClassName(this))
731 .append('(')
732 .append("deadline: ");
733 if (remaining > 0) {
734 buf.append(remaining)
735 .append(" ns later");
736 } else if (remaining < 0) {
737 buf.append(-remaining)
738 .append(" ns ago");
739 } else {
740 buf.append("now");
741 }
742
743 if (isCancelled()) {
744 buf.append(", cancelled");
745 }
746
747 return buf.append(", task: ")
748 .append(task())
749 .append(')')
750 .toString();
751 }
752 }
753
754 /**
755 * Bucket that stores HashedWheelTimeouts. These are stored in a linked-list like datastructure to allow easy
756 * removal of HashedWheelTimeouts in the middle. Also the HashedWheelTimeout act as nodes themself and so no
757 * extra object creation is needed.
758 */
759 private static final class HashedWheelBucket {
760 // Used for the linked-list datastructure
761 private HashedWheelTimeout head;
762 private HashedWheelTimeout tail;
763
764 /**
765 * Add {@link HashedWheelTimeout} to this bucket.
766 */
767 public void addTimeout(HashedWheelTimeout timeout) {
768 assert timeout.bucket == null;
769 timeout.bucket = this;
770 if (head == null) {
771 head = tail = timeout;
772 } else {
773 tail.next = timeout;
774 timeout.prev = tail;
775 tail = timeout;
776 }
777 }
778
779 /**
780 * Expire all {@link HashedWheelTimeout}s for the given {@code deadline}.
781 */
782 public void expireTimeouts(long deadline) {
783 HashedWheelTimeout timeout = head;
784
785 // process all timeouts
786 while (timeout != null) {
787 HashedWheelTimeout next = timeout.next;
788 if (timeout.remainingRounds <= 0) {
789 if (timeout.deadline <= deadline) {
790 timeout.expire();
791 } else {
792 // The timeout was placed into a wrong slot. This should never happen.
793 throw new IllegalStateException(String.format(
794 "timeout.deadline (%d) > deadline (%d)", timeout.deadline, deadline));
795 }
796 } else if (!timeout.isCancelled()) {
797 timeout.remainingRounds --;
798 }
799 timeout = next;
800 }
801 }
802
803 public HashedWheelTimeout remove(HashedWheelTimeout timeout) {
804 HashedWheelTimeout next = timeout.next;
805 // remove timeout that was either processed or cancelled by updating the linked-list
806 if (timeout.prev != null) {
807 timeout.prev.next = next;
808 }
809 if (timeout.next != null) {
810 timeout.next.prev = timeout.prev;
811 }
812
813 if (timeout == head) {
814 // if timeout is also the tail we need to adjust the entry too
815 if (timeout == tail) {
816 tail = null;
817 head = null;
818 } else {
819 head = next;
820 }
821 } else if (timeout == tail) {
822 // if the timeout is the tail modify the tail to be the prev node.
823 tail = timeout.prev;
824 }
825 // null out prev, next and bucket to allow for GC.
826 timeout.prev = null;
827 timeout.next = null;
828 timeout.bucket = null;
829 return next;
830 }
831
832 /**
833 * Clear this bucket and return all not expired / cancelled {@link Timeout}s.
834 */
835 public void clearTimeouts(Set<Timeout> set) {
836 for (;;) {
837 HashedWheelTimeout timeout = pollTimeout();
838 if (timeout == null) {
839 return;
840 }
841 if (timeout.isExpired() || timeout.isCancelled()) {
842 continue;
843 }
844 set.add(timeout);
845 }
846 }
847
848 private HashedWheelTimeout pollTimeout() {
849 HashedWheelTimeout head = this.head;
850 if (head == null) {
851 return null;
852 }
853 HashedWheelTimeout next = head.next;
854 if (next == null) {
855 tail = this.head = null;
856 } else {
857 this.head = next;
858 next.prev = null;
859 }
860
861 // null out prev and next to allow for GC.
862 head.next = null;
863 head.prev = null;
864 head.bucket = null;
865 return head;
866 }
867 }
868 }