com.google.cloud.pubsub.v1.Subscriber Maven / Gradle / Ivy
/*
* 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.AbstractApiService;
import com.google.api.core.ApiClock;
import com.google.api.core.ApiFunction;
import com.google.api.core.ApiService;
import com.google.api.core.BetaApi;
import com.google.api.core.CurrentMillisClock;
import com.google.api.core.InternalApi;
import com.google.api.gax.batching.FlowControlSettings;
import com.google.api.gax.batching.FlowController;
import com.google.api.gax.batching.FlowController.LimitExceededBehavior;
import com.google.api.gax.core.CredentialsProvider;
import com.google.api.gax.core.Distribution;
import com.google.api.gax.core.ExecutorProvider;
import com.google.api.gax.core.FixedExecutorProvider;
import com.google.api.gax.core.InstantiatingExecutorProvider;
import com.google.api.gax.rpc.HeaderProvider;
import com.google.api.gax.rpc.NoHeaderProvider;
import com.google.api.gax.rpc.TransportChannelProvider;
import com.google.api.gax.rpc.UnaryCallSettings;
import com.google.auth.oauth2.GoogleCredentials;
import com.google.cloud.pubsub.v1.stub.GrpcSubscriberStub;
import com.google.cloud.pubsub.v1.stub.SubscriberStub;
import com.google.cloud.pubsub.v1.stub.SubscriberStubSettings;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.pubsub.v1.ProjectSubscriptionName;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.Nullable;
import org.threeten.bp.Duration;
/**
* A Cloud Pub/Sub subscriber that is
* associated with a specific subscription at creation.
*
* A {@link Subscriber} allows you to provide an implementation of a {@link MessageReceiver
* receiver} to which messages are going to be delivered as soon as they are received by the
* subscriber. The delivered messages then can be {@link AckReplyConsumer#ack() acked} or {@link
* AckReplyConsumer#nack() nacked} at will as they get processed by the receiver. Nacking a messages
* implies a later redelivery of such message.
*
*
The subscriber handles the ack management, by automatically extending the ack deadline while
* the message is being processed, to then issue the ack or nack of such message when the processing
* is done (see {@link Builder#setMaxAckExtensionPeriod(Duration)}). Note: message
* redelivery is still possible.
*
*
It also provides customizable options that control:
*
*
* - Ack deadline extension: such as the amount of time ahead to trigger the extension of
* message acknowledgement expiration.
*
- Flow control: such as the maximum outstanding messages or maximum outstanding bytes to keep
* in memory before the receiver either ack or nack them.
*
*
* {@link Subscriber} will use the credentials set on the channel, which uses application default
* credentials through {@link GoogleCredentials#getApplicationDefault} by default.
*
*
{@code Subscriber} is implemented using Guava's
* Service and provides the same methods. See Guava documentation for more
* details.
*/
public class Subscriber extends AbstractApiService {
private static final int THREADS_PER_CHANNEL = 5;
private static final int MAX_INBOUND_MESSAGE_SIZE =
20 * 1024 * 1024; // 20MB API maximum message size.
@InternalApi static final int MAX_ACK_DEADLINE_SECONDS = 600;
@InternalApi static final int MIN_ACK_DEADLINE_SECONDS = 10;
private static final Duration UNARY_TIMEOUT = Duration.ofSeconds(60);
private static final Duration ACK_EXPIRATION_PADDING = Duration.ofSeconds(5);
private static final Logger logger = Logger.getLogger(Subscriber.class.getName());
private final String subscriptionName;
private final FlowControlSettings flowControlSettings;
private final Duration maxAckExtensionPeriod;
// The ExecutorProvider used to generate executors for processing messages.
private final ExecutorProvider executorProvider;
// An instantiation of the SystemExecutorProvider used for processing acks
// and other system actions.
@Nullable private final ScheduledExecutorService alarmsExecutor;
private final Distribution ackLatencyDistribution =
new Distribution(MAX_ACK_DEADLINE_SECONDS + 1);
private SubscriberStub subStub;
private final SubscriberStubSettings subStubSettings;
private final FlowController flowController;
private final int numPullers;
private final MessageReceiver receiver;
private final List streamingSubscriberConnections;
private final ApiClock clock;
private final List closeables = new ArrayList<>();
private Subscriber(Builder builder) {
receiver = builder.receiver;
flowControlSettings = builder.flowControlSettings;
subscriptionName = builder.subscriptionName;
maxAckExtensionPeriod = builder.maxAckExtensionPeriod;
clock = builder.clock.isPresent() ? builder.clock.get() : CurrentMillisClock.getDefaultClock();
flowController =
new FlowController(
builder
.flowControlSettings
.toBuilder()
.setLimitExceededBehavior(LimitExceededBehavior.Block)
.build());
this.numPullers = builder.parallelPullCount;
executorProvider = builder.executorProvider;
ExecutorProvider systemExecutorProvider = builder.systemExecutorProvider;
if (systemExecutorProvider == null) {
systemExecutorProvider =
FixedExecutorProvider.create(
Executors.newScheduledThreadPool(Math.max(6, 2 * numPullers)));
}
alarmsExecutor = systemExecutorProvider.getExecutor();
if (systemExecutorProvider.shouldAutoClose()) {
closeables.add(
new AutoCloseable() {
@Override
public void close() {
alarmsExecutor.shutdown();
}
});
}
TransportChannelProvider channelProvider = builder.channelProvider;
if (channelProvider.acceptsPoolSize()) {
channelProvider = channelProvider.withPoolSize(numPullers);
}
try {
this.subStubSettings =
SubscriberStubSettings.newBuilder()
.setExecutorProvider(systemExecutorProvider)
.setCredentialsProvider(builder.credentialsProvider)
.setTransportChannelProvider(channelProvider)
.setHeaderProvider(builder.headerProvider)
.applyToAllUnaryMethods(
new ApiFunction, Void>() {
@Override
public Void apply(UnaryCallSettings.Builder settingsBuilder) {
settingsBuilder.setSimpleTimeoutNoRetries(UNARY_TIMEOUT);
return null;
}
})
.build();
// TODO(pongad): what about internal header??
} catch (Exception e) {
throw new IllegalStateException(e);
}
streamingSubscriberConnections = new ArrayList(numPullers);
// We regularly look up the distribution for a good subscription deadline.
// So we seed the distribution with something reasonable to start with.
// Distribution is percentile-based, so this value will eventually lose importance.
ackLatencyDistribution.record(60);
}
/**
* Constructs a new {@link Builder}.
*
* @param subscription Cloud Pub/Sub subscription to bind the subscriber to
* @param receiver an implementation of {@link MessageReceiver} used to process the received
* messages
*/
public static Builder newBuilder(ProjectSubscriptionName subscription, MessageReceiver receiver) {
return newBuilder(subscription.toString(), receiver);
}
/**
* Constructs a new {@link Builder}.
*
* @param subscription Cloud Pub/Sub subscription to bind the subscriber to
* @param receiver an implementation of {@link MessageReceiver} used to process the received
* messages
*/
public static Builder newBuilder(String subscription, MessageReceiver receiver) {
return new Builder(subscription, receiver);
}
/** Subscription which the subscriber is subscribed to. */
public String getSubscriptionNameString() {
return subscriptionName;
}
/** The flow control settings the Subscriber is configured with. */
public FlowControlSettings getFlowControlSettings() {
return flowControlSettings;
}
/**
* Initiates service startup and returns immediately.
*
* Example of receiving a specific number of messages.
*
*
{@code
* Subscriber subscriber = Subscriber.newBuilder(subscription, receiver).build();
* subscriber.addListener(new Subscriber.Listener() {
* public void failed(Subscriber.State from, Throwable failure) {
* // Handle error.
* }
* }, executor);
* subscriber.startAsync();
*
* // Wait for a stop signal.
* // In a server, this might be a signal to stop serving.
* // In this example, the signal is just a dummy Future.
* //
* // By default, Subscriber uses daemon threads (see
* // https://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html).
* // Consequently, once other threads have terminated, Subscriber will not stop the JVM from
* // exiting.
* // If the Subscriber should simply run forever, either use the setExecutorProvider method in
* // Subscriber.Builder
* // to use non-daemon threads or run
* // for (;;) {
* // Thread.sleep(Long.MAX_VALUE);
* // }
* // at the end of main() to previent the main thread from exiting.
* done.get();
* subscriber.stopAsync().awaitTerminated();
* }
*/
@Override
public ApiService startAsync() {
// Override only for the docs.
return super.startAsync();
}
@Override
protected void doStart() {
logger.log(Level.FINE, "Starting subscriber group.");
try {
this.subStub = GrpcSubscriberStub.create(subStubSettings);
} catch (IOException e) {
// doesn't matter what we throw, the Service will just catch it and fail to start.
throw new IllegalStateException(e);
}
// When started, connections submit tasks to the executor.
// These tasks must finish before the connections can declare themselves running.
// If we have a single-thread executor and call startStreamingConnections from the
// same executor, it will deadlock: the thread will be stuck waiting for connections
// to start but cannot start the connections.
// For this reason, we spawn a dedicated thread. Starting subscriber should be rare.
new Thread(
new Runnable() {
@Override
public void run() {
try {
startStreamingConnections();
notifyStarted();
} catch (Throwable t) {
notifyFailed(t);
}
}
})
.start();
}
@Override
protected void doStop() {
new Thread(
new Runnable() {
@Override
public void run() {
try {
// stop connection is no-op if connections haven't been started.
stopAllStreamingConnections();
for (AutoCloseable closeable : closeables) {
closeable.close();
}
notifyStopped();
} catch (Exception e) {
notifyFailed(e);
}
}
})
.start();
}
private void startStreamingConnections() {
synchronized (streamingSubscriberConnections) {
for (int i = 0; i < numPullers; i++) {
final ScheduledExecutorService executor = executorProvider.getExecutor();
if (executorProvider.shouldAutoClose()) {
closeables.add(
new AutoCloseable() {
@Override
public void close() {
executor.shutdown();
}
});
}
streamingSubscriberConnections.add(
new StreamingSubscriberConnection(
subscriptionName,
receiver,
ACK_EXPIRATION_PADDING,
maxAckExtensionPeriod,
ackLatencyDistribution,
subStub,
i,
flowController,
executor,
alarmsExecutor,
clock));
}
startConnections(
streamingSubscriberConnections,
new Listener() {
@Override
public void failed(State from, Throwable failure) {
// If a connection failed is because of a fatal error, we should fail the
// whole subscriber.
stopAllStreamingConnections();
try {
notifyFailed(failure);
} catch (IllegalStateException e) {
if (isRunning()) {
throw e;
}
// It could happen that we are shutting down while some channels fail.
}
}
});
}
}
private void stopAllStreamingConnections() {
stopConnections(streamingSubscriberConnections);
}
private void startConnections(
List connections, final ApiService.Listener connectionsListener) {
for (ApiService subscriber : connections) {
subscriber.addListener(connectionsListener, alarmsExecutor);
subscriber.startAsync();
}
for (ApiService subscriber : connections) {
subscriber.awaitRunning();
}
}
private void stopConnections(List connections) {
ArrayList liveConnections;
synchronized (connections) {
liveConnections = new ArrayList(connections);
connections.clear();
}
for (ApiService subscriber : liveConnections) {
subscriber.stopAsync();
}
for (ApiService subscriber : liveConnections) {
try {
subscriber.awaitTerminated();
} catch (IllegalStateException e) {
// If the service fails, awaitTerminated will throw an exception.
// However, we could be stopping services because at least one
// has already failed, so we just ignore this exception.
}
}
}
/** Builder of {@link Subscriber Subscribers}. */
public static final class Builder {
private static final Duration DEFAULT_MAX_ACK_EXTENSION_PERIOD = Duration.ofMinutes(60);
private static final ExecutorProvider DEFAULT_EXECUTOR_PROVIDER =
InstantiatingExecutorProvider.newBuilder()
.setExecutorThreadCount(THREADS_PER_CHANNEL)
.build();
private String subscriptionName;
private MessageReceiver receiver;
private Duration maxAckExtensionPeriod = DEFAULT_MAX_ACK_EXTENSION_PERIOD;
private FlowControlSettings flowControlSettings =
FlowControlSettings.newBuilder().setMaxOutstandingElementCount(1000L).build();
private ExecutorProvider executorProvider = DEFAULT_EXECUTOR_PROVIDER;
private ExecutorProvider systemExecutorProvider = null;
private TransportChannelProvider channelProvider =
SubscriptionAdminSettings.defaultGrpcTransportProviderBuilder()
.setMaxInboundMessageSize(MAX_INBOUND_MESSAGE_SIZE)
.setKeepAliveTime(Duration.ofMinutes(5))
.build();
private HeaderProvider headerProvider = new NoHeaderProvider();
private CredentialsProvider credentialsProvider =
SubscriptionAdminSettings.defaultCredentialsProviderBuilder().build();
private Optional clock = Optional.absent();
private int parallelPullCount = 1;
Builder(String subscriptionName, MessageReceiver receiver) {
this.subscriptionName = subscriptionName;
this.receiver = receiver;
}
/**
* {@code ChannelProvider} to use to create Channels, which must point at Cloud Pub/Sub
* endpoint.
*
* For performance, this client benefits from having multiple channels open at once. Users
* are encouraged to provide instances of {@code ChannelProvider} that creates new channels
* instead of returning pre-initialized ones.
*/
public Builder setChannelProvider(TransportChannelProvider channelProvider) {
this.channelProvider = Preconditions.checkNotNull(channelProvider);
return this;
}
/**
* Sets the static header provider. The header provider will be called during client
* construction only once. The headers returned by the provider will be cached and supplied as
* is for each request issued by the constructed client. Some reserved headers can be overridden
* (e.g. Content-Type) or merged with the default value (e.g. User-Agent) by the underlying
* transport layer.
*
* @param headerProvider the header provider
* @return the builder
*/
@BetaApi
public Builder setHeaderProvider(HeaderProvider headerProvider) {
this.headerProvider = Preconditions.checkNotNull(headerProvider);
return this;
}
/**
* Sets the flow control settings.
*
*
In the example below, the {@link Subscriber} will make sure that
*
*
* - there are at most ten thousand outstanding messages, and
*
- the combined size of outstanding messages does not exceed 1GB.
*
*
* "Outstanding messages" here means the messages that have already been given to {@link
* MessageReceiver} but not yet {@code acked()} or {@code nacked()}.
*
* {@code
* FlowControlSettings flowControlSettings =
* FlowControlSettings.newBuilder()
* .setMaxOutstandingElementCount(10_000L)
* .setMaxOutstandingRequestBytes(1_000_000_000L)
* .build();
* Subscriber subscriber =
* Subscriber.newBuilder(subscriptionName, receiver)
* .setFlowControlSettings(flowControlSettings)
* .build();
* }
*/
public Builder setFlowControlSettings(FlowControlSettings flowControlSettings) {
this.flowControlSettings = Preconditions.checkNotNull(flowControlSettings);
return this;
}
/**
* Set the maximum period a message ack deadline will be extended. Defaults to one hour.
*
* It is recommended to set this value to a reasonable upper bound of the subscriber time to
* process any message. This maximum period avoids messages to be locked by a subscriber
* in cases when the ack reply is lost.
*
*
A zero duration effectively disables auto deadline extensions.
*/
public Builder setMaxAckExtensionPeriod(Duration maxAckExtensionPeriod) {
Preconditions.checkArgument(maxAckExtensionPeriod.toMillis() >= 0);
this.maxAckExtensionPeriod = maxAckExtensionPeriod;
return this;
}
/**
* Gives the ability to set a custom executor. {@link ExecutorProvider#getExecutor()} will be
* called {@link Builder#parallelPullCount} times.
*/
public Builder setExecutorProvider(ExecutorProvider executorProvider) {
this.executorProvider = Preconditions.checkNotNull(executorProvider);
return this;
}
/** {@code CredentialsProvider} to use to create Credentials to authenticate calls. */
public Builder setCredentialsProvider(CredentialsProvider credentialsProvider) {
this.credentialsProvider = Preconditions.checkNotNull(credentialsProvider);
return this;
}
/**
* Gives the ability to set a custom executor for managing lease extensions. If none is provided
* a shared one will be used by all {@link Subscriber} instances.
*/
public Builder setSystemExecutorProvider(ExecutorProvider executorProvider) {
this.systemExecutorProvider = Preconditions.checkNotNull(executorProvider);
return this;
}
/** Sets the number of pullers used to pull messages from the subscription. Defaults to one. */
public Builder setParallelPullCount(int parallelPullCount) {
this.parallelPullCount = parallelPullCount;
return this;
}
/** Gives the ability to set a custom clock. */
Builder setClock(ApiClock clock) {
this.clock = Optional.of(clock);
return this;
}
public Subscriber build() {
return new Subscriber(this);
}
}
}