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.checkInRange;
19 import static io.netty.util.internal.ObjectUtil.checkPositive;
20 import static io.netty.util.internal.ObjectUtil.checkNotNull;
21
22 import io.netty.util.concurrent.ImmediateExecutor;
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 may not be greater than 2^30
337 checkInRange(ticksPerWheel, 1, 1073741824, "ticksPerWheel");
338
339 ticksPerWheel = normalizeTicksPerWheel(ticksPerWheel);
340 HashedWheelBucket[] wheel = new HashedWheelBucket[ticksPerWheel];
341 for (int i = 0; i < wheel.length; i ++) {
342 wheel[i] = new HashedWheelBucket();
343 }
344 return wheel;
345 }
346
347 private static int normalizeTicksPerWheel(int ticksPerWheel) {
348 int normalizedTicksPerWheel = 1;
349 while (normalizedTicksPerWheel < ticksPerWheel) {
350 normalizedTicksPerWheel <<= 1;
351 }
352 return normalizedTicksPerWheel;
353 }
354
355 /**
356 * Starts the background thread explicitly. The background thread will
357 * start automatically on demand even if you did not call this method.
358 *
359 * @throws IllegalStateException if this timer has been
360 * {@linkplain #stop() stopped} already
361 */
362 public void start() {
363 switch (WORKER_STATE_UPDATER.get(this)) {
364 case WORKER_STATE_INIT:
365 if (WORKER_STATE_UPDATER.compareAndSet(this, WORKER_STATE_INIT, WORKER_STATE_STARTED)) {
366 workerThread.start();
367 }
368 break;
369 case WORKER_STATE_STARTED:
370 break;
371 case WORKER_STATE_SHUTDOWN:
372 throw new IllegalStateException("cannot be started once stopped");
373 default:
374 throw new Error("Invalid WorkerState");
375 }
376
377 // Wait until the startTime is initialized by the worker.
378 while (startTime == 0) {
379 try {
380 startTimeInitialized.await();
381 } catch (InterruptedException ignore) {
382 // Ignore - it will be ready very soon.
383 }
384 }
385 }
386
387 @Override
388 public Set<Timeout> stop() {
389 if (Thread.currentThread() == workerThread) {
390 throw new IllegalStateException(
391 HashedWheelTimer.class.getSimpleName() +
392 ".stop() cannot be called from " +
393 TimerTask.class.getSimpleName());
394 }
395
396 if (!WORKER_STATE_UPDATER.compareAndSet(this, WORKER_STATE_STARTED, WORKER_STATE_SHUTDOWN)) {
397 // workerState can be 0 or 2 at this moment - let it always be 2.
398 if (WORKER_STATE_UPDATER.getAndSet(this, WORKER_STATE_SHUTDOWN) != WORKER_STATE_SHUTDOWN) {
399 INSTANCE_COUNTER.decrementAndGet();
400 if (leak != null) {
401 boolean closed = leak.close(this);
402 assert closed;
403 }
404 }
405
406 return Collections.emptySet();
407 }
408
409 try {
410 boolean interrupted = false;
411 while (workerThread.isAlive()) {
412 workerThread.interrupt();
413 try {
414 workerThread.join(100);
415 } catch (InterruptedException ignored) {
416 interrupted = true;
417 }
418 }
419
420 if (interrupted) {
421 Thread.currentThread().interrupt();
422 }
423 } finally {
424 INSTANCE_COUNTER.decrementAndGet();
425 if (leak != null) {
426 boolean closed = leak.close(this);
427 assert closed;
428 }
429 }
430 return worker.unprocessedTimeouts();
431 }
432
433 @Override
434 public Timeout newTimeout(TimerTask task, long delay, TimeUnit unit) {
435 checkNotNull(task, "task");
436 checkNotNull(unit, "unit");
437
438 long pendingTimeoutsCount = pendingTimeouts.incrementAndGet();
439
440 if (maxPendingTimeouts > 0 && pendingTimeoutsCount > maxPendingTimeouts) {
441 pendingTimeouts.decrementAndGet();
442 throw new RejectedExecutionException("Number of pending timeouts ("
443 + pendingTimeoutsCount + ") is greater than or equal to maximum allowed pending "
444 + "timeouts (" + maxPendingTimeouts + ")");
445 }
446
447 start();
448
449 // Add the timeout to the timeout queue which will be processed on the next tick.
450 // During processing all the queued HashedWheelTimeouts will be added to the correct HashedWheelBucket.
451 long deadline = System.nanoTime() + unit.toNanos(delay) - startTime;
452
453 // Guard against overflow.
454 if (delay > 0 && deadline < 0) {
455 deadline = Long.MAX_VALUE;
456 }
457 HashedWheelTimeout timeout = new HashedWheelTimeout(this, task, deadline);
458 timeouts.add(timeout);
459 return timeout;
460 }
461
462 /**
463 * Returns the number of pending timeouts of this {@link Timer}.
464 */
465 public long pendingTimeouts() {
466 return pendingTimeouts.get();
467 }
468
469 private static void reportTooManyInstances() {
470 if (logger.isErrorEnabled()) {
471 String resourceType = simpleClassName(HashedWheelTimer.class);
472 logger.error("You are creating too many " + resourceType + " instances. " +
473 resourceType + " is a shared resource that must be reused across the JVM, " +
474 "so that only a few instances are created.");
475 }
476 }
477
478 private final class Worker implements Runnable {
479 private final Set<Timeout> unprocessedTimeouts = new HashSet<Timeout>();
480
481 private long tick;
482
483 @Override
484 public void run() {
485 // Initialize the startTime.
486 startTime = System.nanoTime();
487 if (startTime == 0) {
488 // We use 0 as an indicator for the uninitialized value here, so make sure it's not 0 when initialized.
489 startTime = 1;
490 }
491
492 // Notify the other threads waiting for the initialization at start().
493 startTimeInitialized.countDown();
494
495 do {
496 final long deadline = waitForNextTick();
497 if (deadline > 0) {
498 int idx = (int) (tick & mask);
499 processCancelledTasks();
500 HashedWheelBucket bucket =
501 wheel[idx];
502 transferTimeoutsToBuckets();
503 bucket.expireTimeouts(deadline);
504 tick++;
505 }
506 } while (WORKER_STATE_UPDATER.get(HashedWheelTimer.this) == WORKER_STATE_STARTED);
507
508 // Fill the unprocessedTimeouts so we can return them from stop() method.
509 for (HashedWheelBucket bucket: wheel) {
510 bucket.clearTimeouts(unprocessedTimeouts);
511 }
512 for (;;) {
513 HashedWheelTimeout timeout = timeouts.poll();
514 if (timeout == null) {
515 break;
516 }
517 if (!timeout.isCancelled()) {
518 unprocessedTimeouts.add(timeout);
519 }
520 }
521 processCancelledTasks();
522 }
523
524 private void transferTimeoutsToBuckets() {
525 // transfer only max. 100000 timeouts per tick to prevent a thread to stale the workerThread when it just
526 // adds new timeouts in a loop.
527 for (int i = 0; i < 100000; i++) {
528 HashedWheelTimeout timeout = timeouts.poll();
529 if (timeout == null) {
530 // all processed
531 break;
532 }
533 if (timeout.state() == HashedWheelTimeout.ST_CANCELLED) {
534 // Was cancelled in the meantime.
535 continue;
536 }
537
538 long calculated = timeout.deadline / tickDuration;
539 timeout.remainingRounds = (calculated - tick) / wheel.length;
540
541 final long ticks = Math.max(calculated, tick); // Ensure we don't schedule for past.
542 int stopIndex = (int) (ticks & mask);
543
544 HashedWheelBucket bucket = wheel[stopIndex];
545 bucket.addTimeout(timeout);
546 }
547 }
548
549 private void processCancelledTasks() {
550 for (;;) {
551 HashedWheelTimeout timeout = cancelledTimeouts.poll();
552 if (timeout == null) {
553 // all processed
554 break;
555 }
556 try {
557 timeout.remove();
558 } catch (Throwable t) {
559 if (logger.isWarnEnabled()) {
560 logger.warn("An exception was thrown while process a cancellation task", t);
561 }
562 }
563 }
564 }
565
566 /**
567 * calculate goal nanoTime from startTime and current tick number,
568 * then wait until that goal has been reached.
569 * @return Long.MIN_VALUE if received a shutdown request,
570 * current time otherwise (with Long.MIN_VALUE changed by +1)
571 */
572 private long waitForNextTick() {
573 long deadline = tickDuration * (tick + 1);
574
575 for (;;) {
576 final long currentTime = System.nanoTime() - startTime;
577 long sleepTimeMs = (deadline - currentTime + 999999) / 1000000;
578
579 if (sleepTimeMs <= 0) {
580 if (currentTime == Long.MIN_VALUE) {
581 return -Long.MAX_VALUE;
582 } else {
583 return currentTime;
584 }
585 }
586
587 // Check if we run on windows, as if thats the case we will need
588 // to round the sleepTime as workaround for a bug that only affect
589 // the JVM if it runs on windows.
590 //
591 // See https://github.com/netty/netty/issues/356
592 if (PlatformDependent.isWindows()) {
593 sleepTimeMs = sleepTimeMs / 10 * 10;
594 if (sleepTimeMs == 0) {
595 sleepTimeMs = 1;
596 }
597 }
598
599 try {
600 Thread.sleep(sleepTimeMs);
601 } catch (InterruptedException ignored) {
602 if (WORKER_STATE_UPDATER.get(HashedWheelTimer.this) == WORKER_STATE_SHUTDOWN) {
603 return Long.MIN_VALUE;
604 }
605 }
606 }
607 }
608
609 public Set<Timeout> unprocessedTimeouts() {
610 return Collections.unmodifiableSet(unprocessedTimeouts);
611 }
612 }
613
614 private static final class HashedWheelTimeout implements Timeout, Runnable {
615
616 private static final int ST_INIT = 0;
617 private static final int ST_CANCELLED = 1;
618 private static final int ST_EXPIRED = 2;
619 private static final AtomicIntegerFieldUpdater<HashedWheelTimeout> STATE_UPDATER =
620 AtomicIntegerFieldUpdater.newUpdater(HashedWheelTimeout.class, "state");
621
622 private final HashedWheelTimer timer;
623 private final TimerTask task;
624 private final long deadline;
625
626 @SuppressWarnings({"unused", "FieldMayBeFinal", "RedundantFieldInitialization" })
627 private volatile int state = ST_INIT;
628
629 // remainingRounds will be calculated and set by Worker.transferTimeoutsToBuckets() before the
630 // HashedWheelTimeout will be added to the correct HashedWheelBucket.
631 long remainingRounds;
632
633 // This will be used to chain timeouts in HashedWheelTimerBucket via a double-linked-list.
634 // As only the workerThread will act on it there is no need for synchronization / volatile.
635 HashedWheelTimeout next;
636 HashedWheelTimeout prev;
637
638 // The bucket to which the timeout was added
639 HashedWheelBucket bucket;
640
641 HashedWheelTimeout(HashedWheelTimer timer, TimerTask task, long deadline) {
642 this.timer = timer;
643 this.task = task;
644 this.deadline = deadline;
645 }
646
647 @Override
648 public Timer timer() {
649 return timer;
650 }
651
652 @Override
653 public TimerTask task() {
654 return task;
655 }
656
657 @Override
658 public boolean cancel() {
659 // only update the state it will be removed from HashedWheelBucket on next tick.
660 if (!compareAndSetState(ST_INIT, ST_CANCELLED)) {
661 return false;
662 }
663 // If a task should be canceled we put this to another queue which will be processed on each tick.
664 // So this means that we will have a GC latency of max. 1 tick duration which is good enough. This way
665 // we can make again use of our MpscLinkedQueue and so minimize the locking / overhead as much as possible.
666 timer.cancelledTimeouts.add(this);
667 return true;
668 }
669
670 void remove() {
671 HashedWheelBucket bucket = this.bucket;
672 if (bucket != null) {
673 bucket.remove(this);
674 } else {
675 timer.pendingTimeouts.decrementAndGet();
676 }
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 timer.taskExecutor.execute(this);
704 } catch (Throwable t) {
705 if (logger.isWarnEnabled()) {
706 logger.warn("An exception was thrown while submit " + TimerTask.class.getSimpleName()
707 + " for execution.", t);
708 }
709 }
710 }
711
712 @Override
713 public void run() {
714 try {
715 task.run(this);
716 } catch (Throwable t) {
717 if (logger.isWarnEnabled()) {
718 logger.warn("An exception was thrown by " + TimerTask.class.getSimpleName() + '.', t);
719 }
720 }
721 }
722
723 @Override
724 public String toString() {
725 final long currentTime = System.nanoTime();
726 long remaining = deadline - currentTime + timer.startTime;
727
728 StringBuilder buf = new StringBuilder(192)
729 .append(simpleClassName(this))
730 .append('(')
731 .append("deadline: ");
732 if (remaining > 0) {
733 buf.append(remaining)
734 .append(" ns later");
735 } else if (remaining < 0) {
736 buf.append(-remaining)
737 .append(" ns ago");
738 } else {
739 buf.append("now");
740 }
741
742 if (isCancelled()) {
743 buf.append(", cancelled");
744 }
745
746 return buf.append(", task: ")
747 .append(task())
748 .append(')')
749 .toString();
750 }
751 }
752
753 /**
754 * Bucket that stores HashedWheelTimeouts. These are stored in a linked-list like datastructure to allow easy
755 * removal of HashedWheelTimeouts in the middle. Also the HashedWheelTimeout act as nodes themself and so no
756 * extra object creation is needed.
757 */
758 private static final class HashedWheelBucket {
759 // Used for the linked-list datastructure
760 private HashedWheelTimeout head;
761 private HashedWheelTimeout tail;
762
763 /**
764 * Add {@link HashedWheelTimeout} to this bucket.
765 */
766 public void addTimeout(HashedWheelTimeout timeout) {
767 assert timeout.bucket == null;
768 timeout.bucket = this;
769 if (head == null) {
770 head = tail = timeout;
771 } else {
772 tail.next = timeout;
773 timeout.prev = tail;
774 tail = timeout;
775 }
776 }
777
778 /**
779 * Expire all {@link HashedWheelTimeout}s for the given {@code deadline}.
780 */
781 public void expireTimeouts(long deadline) {
782 HashedWheelTimeout timeout = head;
783
784 // process all timeouts
785 while (timeout != null) {
786 HashedWheelTimeout next = timeout.next;
787 if (timeout.remainingRounds <= 0) {
788 next = remove(timeout);
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 next = remove(timeout);
798 } else {
799 timeout.remainingRounds --;
800 }
801 timeout = next;
802 }
803 }
804
805 public HashedWheelTimeout remove(HashedWheelTimeout timeout) {
806 HashedWheelTimeout next = timeout.next;
807 // remove timeout that was either processed or cancelled by updating the linked-list
808 if (timeout.prev != null) {
809 timeout.prev.next = next;
810 }
811 if (timeout.next != null) {
812 timeout.next.prev = timeout.prev;
813 }
814
815 if (timeout == head) {
816 // if timeout is also the tail we need to adjust the entry too
817 if (timeout == tail) {
818 tail = null;
819 head = null;
820 } else {
821 head = next;
822 }
823 } else if (timeout == tail) {
824 // if the timeout is the tail modify the tail to be the prev node.
825 tail = timeout.prev;
826 }
827 // null out prev, next and bucket to allow for GC.
828 timeout.prev = null;
829 timeout.next = null;
830 timeout.bucket = null;
831 timeout.timer.pendingTimeouts.decrementAndGet();
832 return next;
833 }
834
835 /**
836 * Clear this bucket and return all not expired / cancelled {@link Timeout}s.
837 */
838 public void clearTimeouts(Set<Timeout> set) {
839 for (;;) {
840 HashedWheelTimeout timeout = pollTimeout();
841 if (timeout == null) {
842 return;
843 }
844 if (timeout.isExpired() || timeout.isCancelled()) {
845 continue;
846 }
847 set.add(timeout);
848 }
849 }
850
851 private HashedWheelTimeout pollTimeout() {
852 HashedWheelTimeout head = this.head;
853 if (head == null) {
854 return null;
855 }
856 HashedWheelTimeout next = head.next;
857 if (next == null) {
858 tail = this.head = null;
859 } else {
860 this.head = next;
861 next.prev = null;
862 }
863
864 // null out prev and next to allow for GC.
865 head.next = null;
866 head.prev = null;
867 head.bucket = null;
868 return head;
869 }
870 }
871 }