/
MessageDispatcher.java
486 lines (435 loc) · 18.2 KB
/
MessageDispatcher.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
/*
* Copyright 2016 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.cloud.pubsub.v1;
import com.google.api.core.ApiClock;
import com.google.api.core.ApiFutureCallback;
import com.google.api.core.ApiFutures;
import com.google.api.core.InternalApi;
import com.google.api.core.SettableApiFuture;
import com.google.api.gax.batching.FlowController;
import com.google.api.gax.batching.FlowController.FlowControlException;
import com.google.api.gax.core.Distribution;
import com.google.common.primitives.Ints;
import com.google.common.util.concurrent.MoreExecutors;
import com.google.pubsub.v1.PubsubMessage;
import com.google.pubsub.v1.ReceivedMessage;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.Executor;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.threeten.bp.Duration;
import org.threeten.bp.Instant;
import org.threeten.bp.temporal.ChronoUnit;
/**
* Dispatches messages to a message receiver while handling the messages acking and lease
* extensions.
*/
class MessageDispatcher {
private static final Logger logger = Logger.getLogger(MessageDispatcher.class.getName());
private static final double PERCENTILE_FOR_ACK_DEADLINE_UPDATES = 99.9;
@InternalApi static final Duration PENDING_ACKS_SEND_DELAY = Duration.ofMillis(100);
private final Executor executor;
private final SequentialExecutorService.AutoExecutor sequentialExecutor;
private final ScheduledExecutorService systemExecutor;
private final ApiClock clock;
private final Duration ackExpirationPadding;
private final Duration maxAckExtensionPeriod;
private final int maxSecondsPerAckExtension;
private final MessageReceiver receiver;
private final AckProcessor ackProcessor;
private final FlowController flowController;
private final Waiter messagesWaiter;
// Maps ID to "total expiration time". If it takes longer than this, stop extending.
private final ConcurrentMap<String, AckHandler> pendingMessages = new ConcurrentHashMap<>();
private final LinkedBlockingQueue<String> pendingAcks = new LinkedBlockingQueue<>();
private final LinkedBlockingQueue<String> pendingNacks = new LinkedBlockingQueue<>();
private final LinkedBlockingQueue<String> pendingReceipts = new LinkedBlockingQueue<>();
// The deadline should be set before use. Here, set it to something unreasonable,
// so we fail loudly if we mess up.
private final AtomicInteger messageDeadlineSeconds = new AtomicInteger(60);
private final AtomicBoolean extendDeadline = new AtomicBoolean(true);
private final Lock jobLock;
private ScheduledFuture<?> backgroundJob;
private ScheduledFuture<?> setExtendedDeadlineFuture;
// To keep track of number of seconds the receiver takes to process messages.
private final Distribution ackLatencyDistribution;
/** Stores the data needed to asynchronously modify acknowledgement deadlines. */
static class PendingModifyAckDeadline {
final List<String> ackIds;
final int deadlineExtensionSeconds;
PendingModifyAckDeadline(int deadlineExtensionSeconds, String... ackIds) {
this(deadlineExtensionSeconds, Arrays.asList(ackIds));
}
private PendingModifyAckDeadline(int deadlineExtensionSeconds, Collection<String> ackIds) {
this.ackIds = new ArrayList<String>(ackIds);
this.deadlineExtensionSeconds = deadlineExtensionSeconds;
}
@Override
public String toString() {
return String.format(
"PendingModifyAckDeadline{extension: %d sec, ackIds: %s}",
deadlineExtensionSeconds, ackIds);
}
}
/** Internal representation of a reply to a Pubsub message, to be sent back to the service. */
public enum AckReply {
ACK,
NACK
}
/** Handles callbacks for acking/nacking messages from the {@link MessageReceiver}. */
private class AckHandler implements ApiFutureCallback<AckReply> {
private final String ackId;
private final int outstandingBytes;
private final long receivedTimeMillis;
private final Instant totalExpiration;
private AckHandler(String ackId, int outstandingBytes, Instant totalExpiration) {
this.ackId = ackId;
this.outstandingBytes = outstandingBytes;
this.receivedTimeMillis = clock.millisTime();
this.totalExpiration = totalExpiration;
}
/** Stop extending deadlines for this message and free flow control. */
private void forget() {
if (pendingMessages.remove(ackId) == null) {
/*
* We're forgetting the message for the second time. Probably because we ran out of total
* expiration, forget the message, then the user finishes working on the message, and forget
* again. Turn the second forget into a no-op so we don't free twice.
*/
return;
}
flowController.release(1, outstandingBytes);
messagesWaiter.incrementPendingCount(-1);
}
@Override
public void onFailure(Throwable t) {
logger.log(
Level.WARNING,
"MessageReceiver failed to process ack ID: " + ackId + ", the message will be nacked.",
t);
pendingNacks.add(ackId);
forget();
}
@Override
public void onSuccess(AckReply reply) {
LinkedBlockingQueue<String> destination;
switch (reply) {
case ACK:
destination = pendingAcks;
// Record the latency rounded to the next closest integer.
ackLatencyDistribution.record(
Ints.saturatedCast(
(long) Math.ceil((clock.millisTime() - receivedTimeMillis) / 1000D)));
break;
case NACK:
destination = pendingNacks;
break;
default:
throw new IllegalArgumentException(String.format("AckReply: %s not supported", reply));
}
destination.add(ackId);
forget();
}
}
interface AckProcessor {
void sendAckOperations(
List<String> acksToSend, List<PendingModifyAckDeadline> ackDeadlineExtensions);
}
MessageDispatcher(
MessageReceiver receiver,
AckProcessor ackProcessor,
Duration ackExpirationPadding,
Duration maxAckExtensionPeriod,
Duration maxDurationPerAckExtension,
Distribution ackLatencyDistribution,
FlowController flowController,
Executor executor,
ScheduledExecutorService systemExecutor,
ApiClock clock) {
this.executor = executor;
this.systemExecutor = systemExecutor;
this.ackExpirationPadding = ackExpirationPadding;
this.maxAckExtensionPeriod = maxAckExtensionPeriod;
this.maxSecondsPerAckExtension = Math.toIntExact(maxDurationPerAckExtension.getSeconds());
this.receiver = receiver;
this.ackProcessor = ackProcessor;
this.flowController = flowController;
// 601 buckets of 1s resolution from 0s to MAX_ACK_DEADLINE_SECONDS
this.ackLatencyDistribution = ackLatencyDistribution;
jobLock = new ReentrantLock();
messagesWaiter = new Waiter();
this.clock = clock;
this.sequentialExecutor = new SequentialExecutorService.AutoExecutor(executor);
}
void start() {
final Runnable setExtendDeadline =
new Runnable() {
@Override
public void run() {
extendDeadline.set(true);
}
};
jobLock.lock();
try {
// Do not adjust deadline concurrently with extendDeadline or processOutstandingAckOperations.
// The following sequence can happen:
// 0. Initially, deadline = 1 min
// 1. Thread A (TA) wants to send receipts, reads deadline = 1m, but stalls before actually
// sending request
// 2. Thread B (TB) adjusts deadline to 2m
// 3. TB calls extendDeadline, modack all messages to 2m, schedules next extension in 2m
// 4. TA sends request, modacking messages to 1m.
// Then messages will expire too early.
// This can be resolved by adding locks in the right places, but at that point,
// we might as well do things sequentially.
backgroundJob =
systemExecutor.scheduleWithFixedDelay(
new Runnable() {
@Override
public void run() {
try {
if (extendDeadline.getAndSet(false)) {
int newDeadlineSec = computeDeadlineSeconds();
messageDeadlineSeconds.set(newDeadlineSec);
extendDeadlines();
if (setExtendedDeadlineFuture != null && !backgroundJob.isDone()) {
setExtendedDeadlineFuture.cancel(true);
}
setExtendedDeadlineFuture =
systemExecutor.schedule(
setExtendDeadline,
newDeadlineSec - ackExpirationPadding.getSeconds(),
TimeUnit.SECONDS);
}
processOutstandingAckOperations();
} catch (Throwable t) {
// Catch everything so that one run failing doesn't prevent subsequent runs.
logger.log(Level.WARNING, "failed to run periodic job", t);
}
}
},
PENDING_ACKS_SEND_DELAY.toMillis(),
PENDING_ACKS_SEND_DELAY.toMillis(),
TimeUnit.MILLISECONDS);
} finally {
jobLock.unlock();
}
}
void stop() {
messagesWaiter.waitComplete();
jobLock.lock();
try {
if (backgroundJob != null) {
backgroundJob.cancel(false);
}
if (setExtendedDeadlineFuture != null) {
setExtendedDeadlineFuture.cancel(true);
}
backgroundJob = null;
setExtendedDeadlineFuture = null;
} finally {
jobLock.unlock();
}
processOutstandingAckOperations();
}
@InternalApi
void setMessageDeadlineSeconds(int sec) {
messageDeadlineSeconds.set(sec);
}
@InternalApi
int getMessageDeadlineSeconds() {
return messageDeadlineSeconds.get();
}
private static class OutstandingMessage {
private final ReceivedMessage receivedMessage;
private final AckHandler ackHandler;
private OutstandingMessage(ReceivedMessage receivedMessage, AckHandler ackHandler) {
this.receivedMessage = receivedMessage;
this.ackHandler = ackHandler;
}
}
void processReceivedMessages(List<ReceivedMessage> messages) {
Instant totalExpiration = now().plus(maxAckExtensionPeriod);
List<OutstandingMessage> outstandingBatch = new ArrayList<>(messages.size());
for (ReceivedMessage message : messages) {
AckHandler ackHandler =
new AckHandler(
message.getAckId(), message.getMessage().getSerializedSize(), totalExpiration);
if (pendingMessages.putIfAbsent(message.getAckId(), ackHandler) != null) {
// putIfAbsent puts ackHandler if ackID isn't previously mapped, then return the
// previously-mapped element.
// If the previous element is not null, we already have the message and the new one is
// definitely a duplicate.
// Don't nack this, because that'd also nack the one we already have in queue.
// Don't update the existing one's total expiration either. If the user "loses" the message,
// we want to eventually
// totally expire so that pubsub service sends us the message again.
continue;
}
outstandingBatch.add(new OutstandingMessage(message, ackHandler));
pendingReceipts.add(message.getAckId());
}
processBatch(outstandingBatch);
}
private void processBatch(List<OutstandingMessage> batch) {
messagesWaiter.incrementPendingCount(batch.size());
for (OutstandingMessage message : batch) {
// This is a blocking flow controller. We have already incremented messagesWaiter, so
// shutdown will block on processing of all these messages anyway.
try {
flowController.reserve(1, message.receivedMessage.getMessage().getSerializedSize());
} catch (FlowControlException unexpectedException) {
// This should be a blocking flow controller and never throw an exception.
throw new IllegalStateException("Flow control unexpected exception", unexpectedException);
}
processOutstandingMessage(addDeliveryInfoCount(message.receivedMessage), message.ackHandler);
}
}
private PubsubMessage addDeliveryInfoCount(ReceivedMessage receivedMessage) {
PubsubMessage originalMessage = receivedMessage.getMessage();
int deliveryAttempt = receivedMessage.getDeliveryAttempt();
// Delivery Attempt will be set to 0 if DeadLetterPolicy is not set on the subscription. In
// this case, do not populate the PubsubMessage with the delivery attempt attribute.
if (deliveryAttempt > 0) {
return PubsubMessage.newBuilder(originalMessage)
.putAttributes("googclient_deliveryattempt", Integer.toString(deliveryAttempt))
.build();
}
return originalMessage;
}
private void processOutstandingMessage(final PubsubMessage message, final AckHandler ackHandler) {
final SettableApiFuture<AckReply> response = SettableApiFuture.create();
final AckReplyConsumer consumer =
new AckReplyConsumer() {
@Override
public void ack() {
response.set(AckReply.ACK);
}
@Override
public void nack() {
response.set(AckReply.NACK);
}
};
ApiFutures.addCallback(response, ackHandler, MoreExecutors.directExecutor());
Runnable deliverMessageTask =
new Runnable() {
@Override
public void run() {
try {
if (ackHandler
.totalExpiration
.plusSeconds(messageDeadlineSeconds.get())
.isBefore(now())) {
// Message expired while waiting. We don't extend these messages anymore,
// so it was probably sent to someone else. Don't work on it.
// Don't nack it either, because we'd be nacking someone else's message.
ackHandler.forget();
return;
}
receiver.receiveMessage(message, consumer);
} catch (Exception e) {
response.setException(e);
}
}
};
if (message.getOrderingKey().isEmpty()) {
executor.execute(deliverMessageTask);
} else {
sequentialExecutor.submit(message.getOrderingKey(), deliverMessageTask);
}
}
/** Compute the ideal deadline, set subsequent modacks to this deadline, and return it. */
@InternalApi
int computeDeadlineSeconds() {
int sec = ackLatencyDistribution.getPercentile(PERCENTILE_FOR_ACK_DEADLINE_UPDATES);
if ((maxSecondsPerAckExtension > 0) && (sec > maxSecondsPerAckExtension)) {
sec = maxSecondsPerAckExtension;
}
// Use Ints.constrainToRange when we get guava 21.
if (sec < Subscriber.MIN_ACK_DEADLINE_SECONDS) {
sec = Subscriber.MIN_ACK_DEADLINE_SECONDS;
} else if (sec > Subscriber.MAX_ACK_DEADLINE_SECONDS) {
sec = Subscriber.MAX_ACK_DEADLINE_SECONDS;
}
return sec;
}
@InternalApi
void extendDeadlines() {
int extendSeconds = getMessageDeadlineSeconds();
List<PendingModifyAckDeadline> modacks = new ArrayList<>();
PendingModifyAckDeadline modack = new PendingModifyAckDeadline(extendSeconds);
Instant now = now();
Instant extendTo = now.plusSeconds(extendSeconds);
for (Map.Entry<String, AckHandler> entry : pendingMessages.entrySet()) {
String ackId = entry.getKey();
Instant totalExpiration = entry.getValue().totalExpiration;
if (totalExpiration.isAfter(extendTo)) {
modack.ackIds.add(ackId);
continue;
}
// forget removes from pendingMessages; this is OK, concurrent maps can
// handle concurrent iterations and modifications.
entry.getValue().forget();
if (totalExpiration.isAfter(now)) {
int sec = Math.max(1, (int) now.until(totalExpiration, ChronoUnit.SECONDS));
modacks.add(new PendingModifyAckDeadline(sec, ackId));
}
}
logger.log(Level.FINER, "Sending {0} modacks", modack.ackIds.size() + modacks.size());
modacks.add(modack);
List<String> acksToSend = Collections.emptyList();
ackProcessor.sendAckOperations(acksToSend, modacks);
}
@InternalApi
void processOutstandingAckOperations() {
List<PendingModifyAckDeadline> modifyAckDeadlinesToSend = new ArrayList<>();
List<String> acksToSend = new ArrayList<>();
pendingAcks.drainTo(acksToSend);
logger.log(Level.FINER, "Sending {0} acks", acksToSend.size());
PendingModifyAckDeadline nacksToSend = new PendingModifyAckDeadline(0);
pendingNacks.drainTo(nacksToSend.ackIds);
logger.log(Level.FINER, "Sending {0} nacks", nacksToSend.ackIds.size());
if (!nacksToSend.ackIds.isEmpty()) {
modifyAckDeadlinesToSend.add(nacksToSend);
}
PendingModifyAckDeadline receiptsToSend =
new PendingModifyAckDeadline(getMessageDeadlineSeconds());
pendingReceipts.drainTo(receiptsToSend.ackIds);
logger.log(Level.FINER, "Sending {0} receipts", receiptsToSend.ackIds.size());
if (!receiptsToSend.ackIds.isEmpty()) {
modifyAckDeadlinesToSend.add(receiptsToSend);
}
ackProcessor.sendAckOperations(acksToSend, modifyAckDeadlinesToSend);
}
private Instant now() {
return Instant.ofEpochMilli(clock.millisTime());
}
}