/
SinglePartitionSubscriber.java
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/
SinglePartitionSubscriber.java
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/*
* Copyright 2021 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.pubsublite.kafka;
import static com.google.common.base.Preconditions.checkState;
import com.google.api.core.ApiFuture;
import com.google.api.core.ApiFutures;
import com.google.cloud.pubsublite.Offset;
import com.google.cloud.pubsublite.Partition;
import com.google.cloud.pubsublite.SequencedMessage;
import com.google.cloud.pubsublite.internal.BlockingPullSubscriber;
import com.google.cloud.pubsublite.internal.CheckedApiException;
import com.google.cloud.pubsublite.internal.CloseableMonitor;
import com.google.cloud.pubsublite.internal.ProxyService;
import com.google.cloud.pubsublite.internal.wire.Committer;
import com.google.cloud.pubsublite.proto.SeekRequest;
import com.google.common.collect.Iterables;
import com.google.common.util.concurrent.MoreExecutors;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.util.ArrayDeque;
import java.util.Optional;
/** Pulls messages and manages commits for a single partition of a subscription. */
class SinglePartitionSubscriber extends ProxyService {
private final PullSubscriberFactory subscriberFactory;
private final Partition partition;
private final Committer committer;
private final boolean enableReset;
private final CloseableMonitor monitor = new CloseableMonitor();
@GuardedBy("monitor.monitor")
private BlockingPullSubscriber subscriber;
@GuardedBy("monitor.monitor")
private boolean needsCommitting = false;
@GuardedBy("monitor.monitor")
private Optional<Offset> lastReceived = Optional.empty();
SinglePartitionSubscriber(
PullSubscriberFactory subscriberFactory,
Partition partition,
SeekRequest initialSeek,
Committer committer,
boolean enableReset)
throws CheckedApiException {
this.subscriberFactory = subscriberFactory;
this.partition = partition;
this.committer = committer;
this.enableReset = enableReset;
this.subscriber =
subscriberFactory.newPullSubscriber(partition, initialSeek, this::onSubscriberReset);
addServices(committer);
}
// ProxyService implementation.
@Override
protected void start() {}
@Override
protected void stop() {
try (CloseableMonitor.Hold h = monitor.enter()) {
subscriber.close();
}
}
@Override
protected void handlePermanentError(CheckedApiException error) {
stop();
}
/** Executes a client-initiated seek. */
void clientSeek(SeekRequest request) throws CheckedApiException {
try (CloseableMonitor.Hold h = monitor.enter()) {
subscriber.close();
subscriber = subscriberFactory.newPullSubscriber(partition, request, this::onSubscriberReset);
}
}
ApiFuture<Void> onData() {
try (CloseableMonitor.Hold h = monitor.enter()) {
return subscriber.onData();
}
}
@GuardedBy("monitor.monitor")
private ArrayDeque<SequencedMessage> pullMessages() throws CheckedApiException {
ArrayDeque<SequencedMessage> messages = new ArrayDeque<>();
for (Optional<SequencedMessage> message = subscriber.messageIfAvailable();
message.isPresent();
message = subscriber.messageIfAvailable()) {
messages.add(message.get());
}
return messages;
}
/** Pulls all available messages. */
ArrayDeque<SequencedMessage> getMessages() throws CheckedApiException {
try (CloseableMonitor.Hold h = monitor.enter()) {
ArrayDeque<SequencedMessage> messages = pullMessages();
if (!messages.isEmpty()) {
lastReceived = Optional.of(Iterables.getLast(messages).offset());
needsCommitting = true;
}
return messages;
}
}
Optional<Long> position() {
try (CloseableMonitor.Hold h = monitor.enter()) {
return lastReceived.map(lastReceived -> lastReceived.value() + 1);
}
}
/** Executes a client-initiated commit. */
ApiFuture<Void> commitOffset(Offset offset) {
return committer.commitOffset(offset);
}
/** Auto-commits the offset of the last received message. */
Optional<ApiFuture<Offset>> autoCommit() {
try (CloseableMonitor.Hold h = monitor.enter()) {
if (!needsCommitting) return Optional.empty();
checkState(lastReceived.isPresent());
needsCommitting = false;
// The Pub/Sub Lite commit offset is one more than the last received.
Offset toCommit = Offset.of(lastReceived.get().value() + 1);
return Optional.of(
ApiFutures.transform(
committer.commitOffset(toCommit),
ignored -> toCommit,
MoreExecutors.directExecutor()));
}
}
private boolean onSubscriberReset() throws CheckedApiException {
if (!enableReset) {
return false;
}
// Handle an out-of-band seek notification from the server. There must be no pending commits
// after this function returns.
try (CloseableMonitor.Hold h = monitor.enter()) {
// Discard undelivered messages.
pullMessages();
// Prevent further auto-commits until post-seek messages are received.
needsCommitting = false;
}
committer.waitUntilEmpty();
return true;
}
}