Pub/Sub client libraries

This page shows how to get started with the Cloud Client Libraries for the Pub/Sub API.

Read more about the client libraries for Cloud APIs in Client Libraries Explained.

Installing the client library

C++

For more information about installing the C++ library, see the GitHub README.

C#

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

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

Go

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

go get cloud.google.com/go/pubsub

Java

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

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>25.3.0</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:25.3.0')

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" % "1.118.0"

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

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

Node.js

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

npm install --save @google-cloud/pubsub

PHP

For more information, see Using PHP on Google Cloud.

composer require google/cloud-pubsub

Python

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

pip install --upgrade google-cloud-pubsub

Ruby

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

gem install google-cloud-pubsub

Setting up authentication

To run the client library, you must first set up authentication. One way to do that is to create a service account and set an environment variable, as shown in the following steps. For other ways to authenticate, see Authenticating as a service account.

Console

Create a service account:

  1. In the Cloud console, go to the Create service account page.

    Go to Create service account
  2. Select your project.

  3. In the Service account name field, enter a name. The Cloud console fills in the Service account ID field based on this name.

    In the Service account description field, enter a description. For example, Service account for quickstart.

  4. Click Create and continue.

  5. To provide access to your project, grant the following role(s) to your service account: Project > Owner.

    In the Select a role list, select a role.

    For additional roles, click Add another role and add each additional role.

  6. Click Continue.

  7. Click Done to finish creating the service account.

    Do not close your browser window. You will use it in the next step.

Create a service account key:

  1. In the Cloud console, click the email address for the service account that you created.
  2. Click Keys.
  3. Click Add key, and then click Create new key.
  4. Click Create. A JSON key file is downloaded to your computer.
  5. Click Close.

gcloud

Set up authentication:

  1. Create the service account. Replace NAME with a name for the service account: 

    gcloud iam service-accounts create NAME

  2. Grant roles to the service account. Run the following command once for each of the following IAM roles: roles/owner: 

    gcloud projects add-iam-policy-binding PROJECT_ID --member="serviceAccount:SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com" --role=ROLE

    Replace the following:

    • SERVICE_ACCOUNT_NAME: the name of the service account
    • PROJECT_ID: the project ID where you created the service account
    • ROLE: the role to grant

  3. Generate the key file: 

    gcloud iam service-accounts keys create FILE_NAME.json --iam-account=SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com

    Replace the following:

    • FILE_NAME: a name for the key file
    • SERVICE_ACCOUNT_NAME: the name of the service account
    • PROJECT_ID: the project ID where you created the service account

Provide authentication credentials to your application code by setting the environment variable GOOGLE_APPLICATION_CREDENTIALS. This variable applies only to your current shell session. If you want the variable to apply to future shell sessions, set the variable in your shell startup file, for example in the ~/.bashrc or ~/.profile file.

Linux or macOS

export GOOGLE_APPLICATION_CREDENTIALS="KEY_PATH"

Replace KEY_PATH with the path of the JSON file that contains your service account key.

For example:

export GOOGLE_APPLICATION_CREDENTIALS="/home/user/Downloads/service-account-file.json"

Windows

For PowerShell:

$env:GOOGLE_APPLICATION_CREDENTIALS="KEY_PATH"

Replace KEY_PATH with the path of the JSON file that contains your service account key.

For example:

$env:GOOGLE_APPLICATION_CREDENTIALS="C:\Users\username\Downloads\service-account-file.json"

For command prompt:

set GOOGLE_APPLICATION_CREDENTIALS=KEY_PATH

Replace KEY_PATH with the path of the JSON file that contains your service account key.

Using the client library

The following example shows how to use the client library.

C++

Before trying this sample, follow the C++ setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub C++ API reference documentation. 

namespace pubsub = ::google::cloud::pubsub;
[](pubsub::TopicAdminClient client, std::string project_id,
   std::string topic_id) {
  auto topic = client.CreateTopic(pubsub::TopicBuilder(
      pubsub::Topic(std::move(project_id), std::move(topic_id))));
  // 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::runtime_error(topic.status().message());

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

C#

Before trying this sample, follow the C# setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub C# API reference documentation. 


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

Before trying this sample, follow the Go setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Go API reference documentation.

If you're using the first generation of the App Engine standard runtime, we recommend using the older Google API Client Libraries. See this GitHub issue for more details. 

// 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

Before trying this sample, follow the Java setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Java API reference documentation. 


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

Before trying this sample, follow the Node.js setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Node.js API reference documentation. 

// 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.publish(Buffer.from('Test message!'));
}

PHP

Before trying this sample, follow the PHP setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub PHP API reference documentation. 

# Includes the autoloader for libraries installed with composer
require __DIR__ . '/vendor/autoload.php';

# Imports the Google Cloud client library
use Google\Cloud\PubSub\PubSubClient;

# Your Google Cloud Platform project ID
$projectId = 'YOUR_PROJECT_ID';

# Instantiates a client
$pubsub = new PubSubClient([
    'projectId' => $projectId
]);

# The name for the new topic
$topicName = 'my-new-topic-2';

# Creates the new topic
$topic = $pubsub->createTopic($topicName);

echo 'Topic ' . $topic->name() . ' created.';

Python

Before trying this sample, follow the Python setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Python API reference documentation. 

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

Before trying this sample, follow the Ruby setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Ruby API reference documentation. 

# 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