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 int state = WORKER_STATE_UPDATER.get(this);
354 switch (state) {
355 case WORKER_STATE_INIT:
356 if (WORKER_STATE_UPDATER.compareAndSet(this, WORKER_STATE_INIT, WORKER_STATE_STARTED)) {
357 workerThread.start();
358 }
359 break;
360 case WORKER_STATE_STARTED:
361 break;
362 case WORKER_STATE_SHUTDOWN:
363 throw new IllegalStateException("cannot be started once stopped");
364 default:
365 throw new Error("Invalid WorkerState: " + state);
366 }
367
368 // Wait until the startTime is initialized by the worker.
369 while (startTime == 0) {
370 try {
371 startTimeInitialized.await();
372 } catch (InterruptedException ignore) {
373 // Ignore - it will be ready very soon.
374 }
375 }
376 }
377
378 @Override
379 public Set<Timeout> stop() {
380 if (Thread.currentThread() == workerThread) {
381 throw new IllegalStateException(
382 HashedWheelTimer.class.getSimpleName() +
383 ".stop() cannot be called from " +
384 TimerTask.class.getSimpleName());
385 }
386
387 if (!WORKER_STATE_UPDATER.compareAndSet(this, WORKER_STATE_STARTED, WORKER_STATE_SHUTDOWN)) {
388 // workerState can be 0 or 2 at this moment - let it always be 2.
389 if (WORKER_STATE_UPDATER.getAndSet(this, WORKER_STATE_SHUTDOWN) != WORKER_STATE_SHUTDOWN) {
390 INSTANCE_COUNTER.decrementAndGet();
391 if (leak != null) {
392 boolean closed = leak.close(this);
393 assert closed;
394 }
395 }
396
397 return Collections.emptySet();
398 }
399
400 try {
401 boolean interrupted = false;
402 while (workerThread.isAlive()) {
403 workerThread.interrupt();
404 try {
405 workerThread.join(100);
406 } catch (InterruptedException ignored) {
407 interrupted = true;
408 }
409 }
410
411 if (interrupted) {
412 Thread.currentThread().interrupt();
413 }
414 } finally {
415 INSTANCE_COUNTER.decrementAndGet();
416 if (leak != null) {
417 boolean closed = leak.close(this);
418 assert closed;
419 }
420 }
421 Set<Timeout> unprocessed = worker.unprocessedTimeouts();
422 Set<Timeout> cancelled = new HashSet<Timeout>(unprocessed.size());
423 for (Timeout timeout : unprocessed) {
424 if (timeout.cancel()) {
425 cancelled.add(timeout);
426 }
427 }
428 return cancelled;
429 }
430
431 @Override
432 public Timeout newTimeout(TimerTask task, long delay, TimeUnit unit) {
433 checkNotNull(task, "task");
434 checkNotNull(unit, "unit");
435
436 long pendingTimeoutsCount = pendingTimeouts.incrementAndGet();
437
438 if (maxPendingTimeouts > 0 && pendingTimeoutsCount > maxPendingTimeouts) {
439 pendingTimeouts.decrementAndGet();
440 throw new RejectedExecutionException("Number of pending timeouts ("
441 + pendingTimeoutsCount + ") is greater than or equal to maximum allowed pending "
442 + "timeouts (" + maxPendingTimeouts + ")");
443 }
444
445 start();
446
447 // Add the timeout to the timeout queue which will be processed on the next tick.
448 // During processing all the queued HashedWheelTimeouts will be added to the correct HashedWheelBucket.
449 long deadline = System.nanoTime() + unit.toNanos(delay) - startTime;
450
451 // Guard against overflow.
452 if (delay > 0 && deadline < 0) {
453 deadline = Long.MAX_VALUE;
454 }
455 HashedWheelTimeout timeout = new HashedWheelTimeout(this, task, deadline);
456 timeouts.add(timeout);
457 return timeout;
458 }
459
460 /**
461 * Returns the number of pending timeouts of this {@link Timer}.
462 */
463 public long pendingTimeouts() {
464 return pendingTimeouts.get();
465 }
466
467 private static void reportTooManyInstances() {
468 if (logger.isErrorEnabled()) {
469 String resourceType = simpleClassName(HashedWheelTimer.class);
470 logger.error("You are creating too many " + resourceType + " instances. " +
471 resourceType + " is a shared resource that must be reused across the JVM, " +
472 "so that only a few instances are created.");
473 }
474 }
475
476 private final class Worker implements Runnable {
477 private final Set<Timeout> unprocessedTimeouts = new HashSet<Timeout>();
478
479 private long tick;
480
481 @Override
482 public void run() {
483 // Initialize the startTime.
484 startTime = System.nanoTime();
485 if (startTime == 0) {
486 // We use 0 as an indicator for the uninitialized value here, so make sure it's not 0 when initialized.
487 startTime = 1;
488 }
489
490 // Notify the other threads waiting for the initialization at start().
491 startTimeInitialized.countDown();
492
493 do {
494 final long deadline = waitForNextTick();
495 if (deadline > 0) {
496 int idx = (int) (tick & mask);
497 processCancelledTasks();
498 HashedWheelBucket bucket =
499 wheel[idx];
500 transferTimeoutsToBuckets();
501 bucket.expireTimeouts(deadline);
502 tick++;
503 }
504 } while (WORKER_STATE_UPDATER.get(HashedWheelTimer.this) == WORKER_STATE_STARTED);
505
506 // Fill the unprocessedTimeouts so we can return them from stop() method.
507 for (HashedWheelBucket bucket: wheel) {
508 bucket.clearTimeouts(unprocessedTimeouts);
509 }
510 for (;;) {
511 HashedWheelTimeout timeout = timeouts.poll();
512 if (timeout == null) {
513 break;
514 }
515 if (!timeout.isCancelled()) {
516 unprocessedTimeouts.add(timeout);
517 }
518 }
519 processCancelledTasks();
520 }
521
522 private void transferTimeoutsToBuckets() {
523 // transfer only max. 100000 timeouts per tick to prevent a thread to stale the workerThread when it just
524 // adds new timeouts in a loop.
525 for (int i = 0; i < 100000; i++) {
526 HashedWheelTimeout timeout = timeouts.poll();
527 if (timeout == null) {
528 // all processed
529 break;
530 }
531 if (timeout.state() == HashedWheelTimeout.ST_CANCELLED) {
532 // Was cancelled in the meantime.
533 continue;
534 }
535
536 long calculated = timeout.deadline / tickDuration;
537 timeout.remainingRounds = (calculated - tick) / wheel.length;
538
539 final long ticks = Math.max(calculated, tick); // Ensure we don't schedule for past.
540 int stopIndex = (int) (ticks & mask);
541
542 HashedWheelBucket bucket = wheel[stopIndex];
543 bucket.addTimeout(timeout);
544 }
545 }
546
547 private void processCancelledTasks() {
548 for (;;) {
549 HashedWheelTimeout timeout = cancelledTimeouts.poll();
550 if (timeout == null) {
551 // all processed
552 break;
553 }
554 try {
555 timeout.removeAfterCancellation();
556 } catch (Throwable t) {
557 if (logger.isWarnEnabled()) {
558 logger.warn("An exception was thrown while process a cancellation task", t);
559 }
560 }
561 }
562 }
563
564 /**
565 * calculate goal nanoTime from startTime and current tick number,
566 * then wait until that goal has been reached.
567 * @return Long.MIN_VALUE if received a shutdown request,
568 * current time otherwise (with Long.MIN_VALUE changed by +1)
569 */
570 private long waitForNextTick() {
571 long deadline = tickDuration * (tick + 1);
572
573 for (;;) {
574 final long currentTime = System.nanoTime() - startTime;
575 long sleepTimeMs = (deadline - currentTime + 999999) / 1000000;
576
577 if (sleepTimeMs <= 0) {
578 if (currentTime == Long.MIN_VALUE) {
579 return -Long.MAX_VALUE;
580 } else {
581 return currentTime;
582 }
583 }
584
585 // Check if we run on windows, as if thats the case we will need
586 // to round the sleepTime as workaround for a bug that only affect
587 // the JVM if it runs on windows.
588 //
589 // See https://github.com/netty/netty/issues/356
590 if (PlatformDependent.isWindows()) {
591 sleepTimeMs = sleepTimeMs / 10 * 10;
592 if (sleepTimeMs == 0) {
593 sleepTimeMs = 1;
594 }
595 }
596
597 try {
598 Thread.sleep(sleepTimeMs);
599 } catch (InterruptedException ignored) {
600 if (WORKER_STATE_UPDATER.get(HashedWheelTimer.this) == WORKER_STATE_SHUTDOWN) {
601 return Long.MIN_VALUE;
602 }
603 }
604 }
605 }
606
607 public Set<Timeout> unprocessedTimeouts() {
608 return Collections.unmodifiableSet(unprocessedTimeouts);
609 }
610 }
611
612 private static final class HashedWheelTimeout implements Timeout, Runnable {
613
614 private static final int ST_INIT = 0;
615 private static final int ST_CANCELLED = 1;
616 private static final int ST_EXPIRED = 2;
617 private static final AtomicIntegerFieldUpdater<HashedWheelTimeout> STATE_UPDATER =
618 AtomicIntegerFieldUpdater.newUpdater(HashedWheelTimeout.class, "state");
619
620 private final HashedWheelTimer timer;
621 private final TimerTask task;
622 private final long deadline;
623
624 @SuppressWarnings({"unused", "FieldMayBeFinal", "RedundantFieldInitialization" })
625 private volatile int state = ST_INIT;
626
627 // remainingRounds will be calculated and set by Worker.transferTimeoutsToBuckets() before the
628 // HashedWheelTimeout will be added to the correct HashedWheelBucket.
629 long remainingRounds;
630
631 // This will be used to chain timeouts in HashedWheelTimerBucket via a double-linked-list.
632 // As only the workerThread will act on it there is no need for synchronization / volatile.
633 HashedWheelTimeout next;
634 HashedWheelTimeout prev;
635
636 // The bucket to which the timeout was added
637 HashedWheelBucket bucket;
638
639 HashedWheelTimeout(HashedWheelTimer timer, TimerTask task, long deadline) {
640 this.timer = timer;
641 this.task = task;
642 this.deadline = deadline;
643 }
644
645 @Override
646 public Timer timer() {
647 return timer;
648 }
649
650 @Override
651 public TimerTask task() {
652 return task;
653 }
654
655 @Override
656 public boolean cancel() {
657 // only update the state it will be removed from HashedWheelBucket on next tick.
658 if (!compareAndSetState(ST_INIT, ST_CANCELLED)) {
659 return false;
660 }
661 // If a task should be canceled we put this to another queue which will be processed on each tick.
662 // So this means that we will have a GC latency of max. 1 tick duration which is good enough. This way
663 // we can make again use of our MpscLinkedQueue and so minimize the locking / overhead as much as possible.
664 timer.cancelledTimeouts.add(this);
665 return true;
666 }
667
668 private void remove() {
669 HashedWheelBucket bucket = this.bucket;
670 if (bucket != null) {
671 bucket.remove(this);
672 }
673 timer.pendingTimeouts.decrementAndGet();
674 }
675 void removeAfterCancellation() {
676 remove();
677 task.cancelled(this);
678 }
679
680 public boolean compareAndSetState(int expected, int state) {
681 return STATE_UPDATER.compareAndSet(this, expected, state);
682 }
683
684 public int state() {
685 return state;
686 }
687
688 @Override
689 public boolean isCancelled() {
690 return state() == ST_CANCELLED;
691 }
692
693 @Override
694 public boolean isExpired() {
695 return state() == ST_EXPIRED;
696 }
697
698 public void expire() {
699 if (!compareAndSetState(ST_INIT, ST_EXPIRED)) {
700 return;
701 }
702
703 try {
704 remove();
705 timer.taskExecutor.execute(this);
706 } catch (Throwable t) {
707 if (logger.isWarnEnabled()) {
708 logger.warn("An exception was thrown while submit " + TimerTask.class.getSimpleName()
709 + " for execution.", t);
710 }
711 }
712 }
713
714 @Override
715 public void run() {
716 try {
717 task.run(this);
718 } catch (Throwable t) {
719 if (logger.isWarnEnabled()) {
720 logger.warn("An exception was thrown by " + TimerTask.class.getSimpleName() + '.', t);
721 }
722 }
723 }
724
725 @Override
726 public String toString() {
727 final long currentTime = System.nanoTime();
728 long remaining = deadline - currentTime + timer.startTime;
729
730 StringBuilder buf = new StringBuilder(192)
731 .append(simpleClassName(this))
732 .append('(')
733 .append("deadline: ");
734 if (remaining > 0) {
735 buf.append(remaining)
736 .append(" ns later");
737 } else if (remaining < 0) {
738 buf.append(-remaining)
739 .append(" ns ago");
740 } else {
741 buf.append("now");
742 }
743
744 if (isCancelled()) {
745 buf.append(", cancelled");
746 }
747
748 return buf.append(", task: ")
749 .append(task())
750 .append(')')
751 .toString();
752 }
753 }
754
755 /**
756 * Bucket that stores HashedWheelTimeouts. These are stored in a linked-list like datastructure to allow easy
757 * removal of HashedWheelTimeouts in the middle. Also the HashedWheelTimeout act as nodes themself and so no
758 * extra object creation is needed.
759 */
760 private static final class HashedWheelBucket {
761 // Used for the linked-list datastructure
762 private HashedWheelTimeout head;
763 private HashedWheelTimeout tail;
764
765 /**
766 * Add {@link HashedWheelTimeout} to this bucket.
767 */
768 public void addTimeout(HashedWheelTimeout timeout) {
769 assert timeout.bucket == null;
770 timeout.bucket = this;
771 if (head == null) {
772 head = tail = timeout;
773 } else {
774 tail.next = timeout;
775 timeout.prev = tail;
776 tail = timeout;
777 }
778 }
779
780 /**
781 * Expire all {@link HashedWheelTimeout}s for the given {@code deadline}.
782 */
783 public void expireTimeouts(long deadline) {
784 HashedWheelTimeout timeout = head;
785
786 // process all timeouts
787 while (timeout != null) {
788 HashedWheelTimeout next = timeout.next;
789 if (timeout.remainingRounds <= 0) {
790 if (timeout.deadline <= deadline) {
791 timeout.expire();
792 } else {
793 // The timeout was placed into a wrong slot. This should never happen.
794 throw new IllegalStateException(String.format(
795 "timeout.deadline (%d) > deadline (%d)", timeout.deadline, deadline));
796 }
797 } else if (!timeout.isCancelled()) {
798 timeout.remainingRounds --;
799 }
800 timeout = next;
801 }
802 }
803
804 public HashedWheelTimeout remove(HashedWheelTimeout timeout) {
805 HashedWheelTimeout next = timeout.next;
806 // remove timeout that was either processed or cancelled by updating the linked-list
807 if (timeout.prev != null) {
808 timeout.prev.next = next;
809 }
810 if (timeout.next != null) {
811 timeout.next.prev = timeout.prev;
812 }
813
814 if (timeout == head) {
815 // if timeout is also the tail we need to adjust the entry too
816 if (timeout == tail) {
817 tail = null;
818 head = null;
819 } else {
820 head = next;
821 }
822 } else if (timeout == tail) {
823 // if the timeout is the tail modify the tail to be the prev node.
824 tail = timeout.prev;
825 }
826 // null out prev, next and bucket to allow for GC.
827 timeout.prev = null;
828 timeout.next = null;
829 timeout.bucket = null;
830 return next;
831 }
832
833 /**
834 * Clear this bucket and return all not expired / cancelled {@link Timeout}s.
835 */
836 public void clearTimeouts(Set<Timeout> set) {
837 for (;;) {
838 HashedWheelTimeout timeout = pollTimeout();
839 if (timeout == null) {
840 return;
841 }
842 if (timeout.isExpired() || timeout.isCancelled()) {
843 continue;
844 }
845 set.add(timeout);
846 }
847 }
848
849 private HashedWheelTimeout pollTimeout() {
850 HashedWheelTimeout head = this.head;
851 if (head == null) {
852 return null;
853 }
854 HashedWheelTimeout next = head.next;
855 if (next == null) {
856 tail = this.head = null;
857 } else {
858 this.head = next;
859 next.prev = null;
860 }
861
862 // null out prev and next to allow for GC.
863 head.next = null;
864 head.prev = null;
865 head.bucket = null;
866 return head;
867 }
868 }
869 }