Pub/Sub client libraries

This page shows how to get started with the Cloud Client Libraries for the Pub/Sub API. Client libraries make it easier to access Google Cloud APIs from a supported language. Although you can use Google Cloud APIs directly by making raw requests to the server, client libraries provide simplifications that significantly reduce the amount of code you need to write.

Note: Instructions on this page apply to the Python 3 and Java 8 App Engine standard environments. To use Python 2 with App Engine Standard, see this sample.

Read more about the Cloud Client Libraries and the older Google API Client Libraries in Client libraries explained.

Install the client library

C++

For information about this client library's requirements and install dependencies, see Setting up a C++ development environment.

C#

Install-Package Google.Cloud.PubSub.V1 -Pre

For more information, see Setting Up a C# Development Environment.

Go

go get cloud.google.com/go/pubsub

For more information, see Setting Up a Go Development Environment.

Java

If you are using Maven, add the following to your pom.xml file. For more information about BOMs, see The Google Cloud Platform Libraries BOM.

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>libraries-bom</artifactId>
      <version>26.49.0</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>google-cloud-pubsub</artifactId>
  </dependency>

</dependencies>

If you are using Gradle, add the following to your dependencies:

implementation platform('com.google.cloud:libraries-bom:26.49.0')

implementation 'com.google.cloud:google-cloud-pubsub'

If you are using sbt, add the following to your dependencies:

libraryDependencies += "com.google.cloud" % "google-cloud-pubsub" % "1.134.1"

If you're using Visual Studio Code, IntelliJ, or Eclipse, you can add client libraries to your project using the following IDE plugins:

• Cloud Code for VS Code
• Cloud Code for IntelliJ
• Cloud Tools for Eclipse

The plugins provide additional functionality, such as key management for service accounts. Refer to each plugin's documentation for details.

Note: Cloud Java client libraries do not currently support Android.

For more information, see Setting Up a Java Development Environment.

Node.js

npm install --save @google-cloud/pubsub

For more information, see Setting Up a Node.js Development Environment.

PHP

composer require google/cloud-pubsub

For more information, see Using PHP on Google Cloud.

Python

pip install --upgrade google-cloud-pubsub

For more information, see Setting Up a Python Development Environment.

Ruby

gem install google-cloud-pubsub

For more information, see Setting Up a Ruby Development Environment.

Set up authentication

To authenticate calls to Google Cloud APIs, client libraries support Application Default Credentials (ADC); the libraries look for credentials in a set of defined locations and use those credentials to authenticate requests to the API. With ADC, you can make credentials available to your application in a variety of environments, such as local development or production, without needing to modify your application code.

For production environments, the way you set up ADC depends on the service and context. For more information, see Set up Application Default Credentials.

For a local development environment, you can set up ADC with the credentials that are associated with your Google Account:

1. Install the Google Cloud CLI, then initialize it by running the following command:

   gcloud init

2. If you're using a local shell, then create local authentication credentials for your user account:

   gcloud auth application-default login

   You don't need to do this if you're using Cloud Shell.

   A sign-in screen appears. After you sign in, your credentials are stored in the local credential file used by ADC.

Use the client library

The following example shows how to use the client library to create a Pub/Sub topic.

C++

namespace pubsub = ::google::cloud::pubsub;
namespace pubsub_admin = ::google::cloud::pubsub_admin;
[](pubsub_admin::TopicAdminClient client, std::string project_id,
   std::string topic_id) {
  auto topic = client.CreateTopic(
      pubsub::Topic(std::move(project_id), std::move(topic_id)).FullName());
  // Note that kAlreadyExists is a possible error when the library retries.
  if (topic.status().code() == google::cloud::StatusCode::kAlreadyExists) {
    std::cout << "The topic already exists\n";
    return;
  }
  if (!topic) throw std::move(topic).status();

  std::cout << "The topic was successfully created: " << topic->DebugString()
            << "\n";
}

C#

using Google.Cloud.PubSub.V1;
using Grpc.Core;
using System;

public class CreateTopicSample
{
    public Topic CreateTopic(string projectId, string topicId)
    {
        PublisherServiceApiClient publisher = PublisherServiceApiClient.Create();
        var topicName = TopicName.FromProjectTopic(projectId, topicId);
        Topic topic = null;

        try
        {
            topic = publisher.CreateTopic(topicName);
            Console.WriteLine($"Topic {topic.Name} created.");
        }
        catch (RpcException e) when (e.Status.StatusCode == StatusCode.AlreadyExists)
        {
            Console.WriteLine($"Topic {topicName} already exists.");
        }
        return topic;
    }
}

Go

// Sample pubsub-quickstart creates a Google Cloud Pub/Sub topic.
package main

import (
	"context"
	"fmt"
	"log"

	"cloud.google.com/go/pubsub"
)

func main() {
	ctx := context.Background()

	// Sets your Google Cloud Platform project ID.
	projectID := "YOUR_PROJECT_ID"

	// Creates a client.
	client, err := pubsub.NewClient(ctx, projectID)
	if err != nil {
		log.Fatalf("Failed to create client: %v", err)
	}
	defer client.Close()

	// Sets the id for the new topic.
	topicID := "my-topic"

	// Creates the new topic.
	topic, err := client.CreateTopic(ctx, topicID)
	if err != nil {
		log.Fatalf("Failed to create topic: %v", err)
	}

	fmt.Printf("Topic %v created.\n", topic)
}

Java

import com.google.cloud.pubsub.v1.TopicAdminClient;
import com.google.pubsub.v1.Topic;
import com.google.pubsub.v1.TopicName;
import java.io.IOException;

public class CreateTopicExample {
  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String topicId = "your-topic-id";

    createTopicExample(projectId, topicId);
  }

  public static void createTopicExample(String projectId, String topicId) throws IOException {
    try (TopicAdminClient topicAdminClient = TopicAdminClient.create()) {
      TopicName topicName = TopicName.of(projectId, topicId);
      Topic topic = topicAdminClient.createTopic(topicName);
      System.out.println("Created topic: " + topic.getName());
    }
  }
}

Node.js

// Imports the Google Cloud client library
const {PubSub} = require('@google-cloud/pubsub');

async function quickstart(
  projectId = 'your-project-id', // Your Google Cloud Platform project ID
  topicNameOrId = 'my-topic', // Name for the new topic to create
  subscriptionName = 'my-sub' // Name for the new subscription to create
) {
  // Instantiates a client
  const pubsub = new PubSub({projectId});

  // Creates a new topic
  const [topic] = await pubsub.createTopic(topicNameOrId);
  console.log(`Topic ${topic.name} created.`);

  // Creates a subscription on that new topic
  const [subscription] = await topic.createSubscription(subscriptionName);

  // Receive callbacks for new messages on the subscription
  subscription.on('message', message => {
    console.log('Received message:', message.data.toString());
    process.exit(0);
  });

  // Receive callbacks for errors on the subscription
  subscription.on('error', error => {
    console.error('Received error:', error);
    process.exit(1);
  });

  // Send a message to the topic
  topic.publishMessage({data: Buffer.from('Test message!')});
}

Python

from google.cloud import pubsub_v1

# TODO(developer)
# project_id = "your-project-id"
# topic_id = "your-topic-id"

publisher = pubsub_v1.PublisherClient()
topic_path = publisher.topic_path(project_id, topic_id)

topic = publisher.create_topic(request={"name": topic_path})

print(f"Created topic: {topic.name}")

Ruby

# Imports the Google Cloud client library
require "google/cloud/pubsub"

# Instantiates a client
pubsub = Google::Cloud::Pubsub.new

# The name for the new topic
# topic_id = "your-topic-id"

# Creates the new topic
topic = pubsub.create_topic topic_id

puts "Topic #{topic.name} created."

Additional resources

C++

The following list contains links to more resources related to the client library for C++:

• API reference
• Client libraries best practices
• Issue tracker
• google-cloud-pubsub on Stack Overflow
• Source code

C#

The following list contains links to more resources related to the client library for C#:

• API reference
• Client libraries best practices
• Issue tracker
• google-cloud-pubsub on Stack Overflow
• Source code

Go

The following list contains links to more resources related to the client library for Go:

• API reference
• Client libraries best practices
• Issue tracker
• google-cloud-pubsub on Stack Overflow
• Source code

Java

The following list contains links to more resources related to the client library for Java:

• API reference
• Client libraries best practices
• Issue tracker
• google-cloud-pubsub on Stack Overflow
• Source code

Node.js

The following list contains links to more resources related to the client library for Node.js:

• API reference
• Client libraries best practices
• Issue tracker
• google-cloud-pubsub on Stack Overflow
• Source code

PHP

The following list contains links to more resources related to the client library for PHP:

• API reference
• Client libraries best practices
• Issue tracker
• google-cloud-pubsub on Stack Overflow
• Source code

Python

The following list contains links to more resources related to the client library for Python:

• API reference
• Client libraries best practices
• Issue tracker
• google-cloud-pubsub on Stack Overflow
• Source code

Ruby

The following list contains links to more resources related to the client library for Ruby:

• API reference
• Client libraries best practices
• Issue tracker
• google-cloud-pubsub on Stack Overflow
• Source code

Additional Pub/Sub API libraries

Language	Library
Java	java-pubsub-group-kafka-connector