Google Cloud Pub/Sub Lite Client for Java

Java idiomatic client for Cloud Pub/Sub Lite.

• Product Documentation
• Client Library Documentation

Note: This client is a work-in-progress, and may occasionally make backwards-incompatible changes.

Quickstart

If you are using Maven, add this to your pom.xml file:

<dependency>
  <groupId>com.google.cloud</groupId>
  <artifactId>google-cloud-pubsublite</artifactId>
  <version>0.16.1</version>
</dependency>
<dependency>
  <groupId>com.google.cloud</groupId>
  <artifactId>google-cloud-pubsub</artifactId>
  <version>1.113.5</version>
</dependency>

If you are using Gradle without BOM, add this to your dependencies

compile 'com.google.cloud:google-cloud-pubsublite:0.16.1'

If you are using SBT, add this to your dependencies

libraryDependencies += "com.google.cloud" % "google-cloud-pubsublite" % "0.16.1"

Authentication

See the Authentication section in the base directory's README.

Getting Started

Prerequisites

You will need a Google Cloud Platform Console project with the Cloud Pub/Sub Lite API enabled. You will need to enable billing to use Google Cloud Pub/Sub Lite. Follow these instructions to get your project set up. You will also need to set up the local development environment by installing the Google Cloud SDK and running the following commands in command line: gcloud auth login and gcloud config set project [YOUR PROJECT ID].

Installation and setup

You'll need to obtain the google-cloud-pubsublite library. See the Quickstart section to add google-cloud-pubsublite as a dependency in your code.

About Cloud Pub/Sub Lite

Google Pub/Sub Lite is designed to provide reliable, many-to-many, asynchronous messaging between applications. Publisher applications can send messages to a topic and other applications can subscribe to that topic to receive the messages. By decoupling senders and receivers, Google Cloud Pub/Sub allows developers to communicate between independently written applications.

Compared to Google Pub/Sub, Pub/Sub Lite provides partitioned zonal data storage with predefined capacity. Both products present a similar API, but Pub/Sub Lite has more usage caveats.

See the Google Pub/Sub Lite docs for more details on how to activate Pub/Sub Lite for your project, as well as guidance on how to choose between Cloud Pub/Sub and Pub/Sub Lite.

Creating a topic

With Pub/Sub Lite you can create topics. A topic is a named resource to which messages are sent by publishers. Add the following imports at the top of your file:

import com.google.cloud.pubsublite.*;
import com.google.cloud.pubsublite.proto.Topic;
import com.google.cloud.pubsublite.proto.Topic.*;
import com.google.protobuf.util.Durations;

Then, to create the topic, use the following code:

// TODO(developer): Replace these variables with your own.
long projectNumber = 123L;
String cloudRegion = "us-central1";
char zoneId = 'b';
String topicId = "your-topic-id";
Integer partitions = 1;

TopicPath topicPath =
    TopicPath.newBuilder()
        .setProject(ProjectNumber.of(projectNumber))
        .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
        .setName(TopicName.of(topicId))
        .build();

Topic topic =
    Topic.newBuilder()
        .setPartitionConfig(
            PartitionConfig.newBuilder()
                // Set publishing throughput to 1 times the standard partition
                // throughput of 4 MiB per sec. This must be in the range [1,4]. A
                // topic with `scale` of 2 and count of 10 is charged for 20 partitions.
                .setScale(1)
                .setCount(partitions))
        .setRetentionConfig(
            RetentionConfig.newBuilder()
                // How long messages are retained.
                .setPeriod(Durations.fromDays(1))
                // Set storage per partition to 30 GiB. This must be 30 GiB-10 TiB.
                // If the number of bytes stored in any of the topic's partitions grows
                // beyond this value, older messages will be dropped to make room for
                // newer ones, regardless of the value of `period`.
                .setPerPartitionBytes(30 * 1024 * 1024 * 1024L))
        .setName(topicPath.toString())
        .build();

AdminClientSettings adminClientSettings =
    AdminClientSettings.newBuilder().setRegion(CloudRegion.of(cloudRegion)).build();

try (AdminClient adminClient = AdminClient.create(adminClientSettings)) {
  Topic response = adminClient.createTopic(topic).get();
  System.out.println(response.getAllFields() + "created successfully.");
}

Publishing messages

With Pub/Sub Lite, you can publish messages to a topic. Add the following import at the top of your file:

import com.google.api.core.*;
import com.google.cloud.pubsublite.*;
import com.google.cloud.pubsublite.cloudpubsub.*;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.PubsubMessage;
import java.util.*;

Then, to publish messages asynchronously, use the following code:

// TODO(developer): Replace these variables before running the sample.
long projectNumber = 123L;
String cloudRegion = "us-central1";
char zoneId = 'b';
// Choose an existing topic.
String topicId = "your-topic-id";
int messageCount = 100;

TopicPath topicPath =
    TopicPath.newBuilder()
        .setProject(ProjectNumber.of(projectNumber))
        .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
        .setName(TopicName.of(topicId))
        .build();
Publisher publisher = null;
List<ApiFuture<String>> futures = new ArrayList<>();

try {
  PublisherSettings publisherSettings =
      PublisherSettings.newBuilder().setTopicPath(topicPath).build();

  publisher = Publisher.create(publisherSettings);

  // Start the publisher. Upon successful starting, its state will become RUNNING.
  publisher.startAsync().awaitRunning();

  for (int i = 0; i < messageCount; i++) {
    String message = "message-" + i;

    // Convert the message to a byte string.
    ByteString data = ByteString.copyFromUtf8(message);
    PubsubMessage pubsubMessage = PubsubMessage.newBuilder().setData(data).build();

    // Publish a message. Messages are automatically batched.
    ApiFuture<String> future = publisher.publish(pubsubMessage);
    futures.add(future);
  }
} finally {
  ArrayList<MessageMetadata> metadata = new ArrayList<>();
  List<String> ackIds = ApiFutures.allAsList(futures).get();
  for (String id : ackIds) {
    // Decoded metadata contains partition and offset.
    metadata.add(MessageMetadata.decode(id));
  }
  System.out.println(metadata + "\nPublished " + ackIds.size() + " messages.");

  if (publisher != null) {
    // Shut down the publisher.
    publisher.stopAsync().awaitTerminated();
    System.out.println("Publisher is shut down.");
  }
}

Creating a subscription

With Pub/Sub Lite you can create subscriptions. A subscription represents the stream of messages from a single, specific topic. Add the following imports at the top of your file:

import com.google.cloud.pubsublite.*;
import com.google.cloud.pubsublite.proto.Subscription;
import com.google.cloud.pubsublite.proto.Subscription.*;
import com.google.cloud.pubsublite.proto.Subscription.DeliveryConfig.*;

Then, to create the subscription, use the following code:

// TODO(developer): Replace these variables with your own.
long projectNumber = 123L;
String cloudRegion = "us-central1";
char zoneId = 'b';
// Choose an existing topic.
String topicId = "your-topic-id";
String subscriptionId = "your-subscription-id";

TopicPath topicPath =
    TopicPath.newBuilder()
        .setProject(ProjectNumber.of(projectNumber))
        .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
        .setName(TopicName.of(topicId))
        .build();

SubscriptionPath subscriptionPath =
    SubscriptionPath.newBuilder()
        .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
        .setProject(ProjectNumber.of(projectNumber))
        .setName(SubscriptionName.of(subscriptionId))
        .build();

Subscription subscription =
    Subscription.newBuilder()
        .setDeliveryConfig(
            // The server does not wait for a published message to be successfully
            // written to storage before delivering it to subscribers. As such, a
            // subscriber may receive a message for which the write to storage failed.
            // If the subscriber re-reads the offset of that message later on, there
            // may be a gap at that offset.
            DeliveryConfig.newBuilder()
                .setDeliveryRequirement(DeliveryRequirement.DELIVER_IMMEDIATELY))
        .setName(subscriptionPath.toString())
        .setTopic(topicPath.toString())
        .build();

AdminClientSettings adminClientSettings =
    AdminClientSettings.newBuilder().setRegion(CloudRegion.of(cloudRegion)).build();

try (AdminClient adminClient = AdminClient.create(adminClientSettings)) {
  Subscription response = adminClient.createSubscription(subscription).get();
  System.out.println(response.getAllFields() + "created successfully.");
}

Receiving messages

With Pub/Sub Lite you can receive messages from a subscription. Add the following imports at the top of your file:

import com.google.cloud.pubsub.v1.AckReplyConsumer;
import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsublite.*;
import com.google.cloud.pubsublite.cloudpubsub.*;
import com.google.common.util.concurrent.MoreExecutors;
import com.google.pubsub.v1.PubsubMessage;
import java.util.*;

Then, to pull messages asynchronously, use the following code:

// TODO(developer): Replace these variables with your own.
long projectNumber = 123L;
String cloudRegion = "us-central1";
char zoneId = 'b';
// Choose an existing topic.
String topicId = "your-topic-id";
// Choose an existing subscription.
String subscriptionId = "your-subscription-id";

SubscriptionPath subscriptionPath =
    SubscriptionPath.newBuilder()
        .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
        .setProject(ProjectNumber.of(projectNumber))
        .setName(SubscriptionName.of(subscriptionId))
        .build();

// The message stream is paused based on the maximum size or number of messages that the
// subscriber has already received, whichever condition is met first.
FlowControlSettings flowControlSettings =
    FlowControlSettings.builder()
        // 10 MiB. Must be greater than the allowed size of the largest message (1 MiB).
        .setBytesOutstanding(10 * 1024 * 1024L)
        // 1,000 outstanding messages. Must be >0.
        .setMessagesOutstanding(1000L)
        .build();

MessageReceiver receiver =
    (PubsubMessage message, AckReplyConsumer consumer) -> {
      System.out.println("Id : " + message.getMessageId());
      System.out.println("Data : " + message.getData().toStringUtf8());
      consumer.ack();
    };

SubscriberSettings subscriberSettings =
    SubscriberSettings.newBuilder()
        .setSubscriptionPath(subscriptionPath)
        .setReceiver(receiver)
        // Flow control settings are set at the partition level.
        .setPerPartitionFlowControlSettings(flowControlSettings)
        .build();

Subscriber subscriber = Subscriber.create(subscriberSettings);

// Start the subscriber. Upon successful starting, its state will become RUNNING.
subscriber.startAsync().awaitRunning();

System.out.println("Listening to messages on " + subscriptionPath.toString() + "...");

try {
  System.out.println(subscriber.state());
  // Wait 90 seconds for the subscriber to reach TERMINATED state. If it encounters
  // unrecoverable errors before then, its state will change to FAILED and an
  // IllegalStateException will be thrown.
  subscriber.awaitTerminated(90, TimeUnit.SECONDS);
} catch (TimeoutException t) {
  // Shut down the subscriber. This will change the state of the subscriber to TERMINATED.
  subscriber.stopAsync().awaitTerminated();
  System.out.println("Subscriber is shut down: " + subscriber.state());
}

Samples

Samples are in the samples/ directory. The samples' README.md has instructions for running the samples.

Sample	Source Code	Try it
Create Subscription Example	source code
Create Topic Example	source code
Delete Subscription Example	source code
Delete Topic Example	source code
Get Subscription Example	source code
Get Topic Example	source code
List Subscriptions In Project Example	source code
List Subscriptions In Topic Example	source code
List Topics Example	source code
Publish With Batch Settings Example	source code
Publish With Custom Attributes Example	source code
Publish With Ordering Key Example	source code
Publisher Example	source code
Subscriber Example	source code
Update Subscription Example	source code
Update Topic Example	source code
Read Messages Example	source code
Write Messages Example	source code

Troubleshooting

To get help, follow the instructions in the shared Troubleshooting document.

Transport

Cloud Pub/Sub Lite uses gRPC for the transport layer.

Java Versions

Java 8 or above is required for using this client.

Versioning

This library follows Semantic Versioning.

It is currently in major version zero (0.y.z), which means that anything may change at any time and the public API should not be considered stable.

Contributing

Contributions to this library are always welcome and highly encouraged.

See CONTRIBUTING for more information how to get started.

Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms. See Code of Conduct for more information.

License

Apache 2.0 - See LICENSE for more information.

CI Status

Java Version	Status
Java 8
Java 8 OSX
Java 8 Windows
Java 11

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