Create a topic

Within Pub/Sub, a topic is a named resource that represents a feed of messages. You must create a topic before you can publish or subscribe to it. Pub/Sub supports two kinds of topics: a standard topic and an import topic.

This document describes how to create a Pub/Sub standard topic. If you want to learn more about an import topic and how to create one, see About import topics.

To create a topic you can use the Google Cloud console, the Google Cloud CLI, the client library, or the Pub/Sub API.

Before you begin

• Learn about the Pub/Sub service and its terminology.

• Learn about the publish process.

Required roles and permissions to manage topics

To get the permissions that you need to create and manage topics, ask your administrator to grant you the Pub/Sub Editor(roles/pubsub.editor) IAM role on your topic or project. For more information about granting roles, see Manage access to projects, folders, and organizations.

This predefined role contains the permissions required to create and manage topics. To see the exact permissions that are required, expand the Required permissions section:

You might also be able to get these permissions with custom roles or other predefined roles.

You can configure access control at the project level and at the individual resource level. You can create a subscription in one project and attach it to a topic located in a different project. Ensure that you have the required permissions for each project.

Properties of a topic

When you create or update a topic, you must specify its properties.

Add a default subscription

Adds a default subscription to the Pub/Sub topic. You can create another subscription for the topic after the topic is created. The default subscription has the following properties:

• Subscription ID of -sub
• Pull delivery type
• Message retention duration of seven days
• Expiration after 31 days of inactivity
• Acknowledgment deadline of 10 seconds
• Immediate retry policy

Use a schema

A schema is a format that the message data field must follow. A schema is a contract between the publisher and subscriber that Pub/Sub enforces. Topic schemas help standardize message types and permissions to allow them to be consumed by different teams in your organization. Pub/Sub creates a central authority for message types and permissions. To create a topic with schema, see Schema overview.

Enable ingestion

Enabling this property lets you ingest streaming data from external sources into a topic so that you can use the features of Google Cloud. To create an import topic for ingestion, see the following:

• Create an Amazon Kinesis Data Streams import topic

• Create a Cloud Storage import topic

Enable message retention

Specifies how long the Pub/Sub topic retains messages after publication. After the message retention duration is over, Pub/Sub might discard the message regardless of its acknowledgment state. Message storage fees are charged for storing all messages published to the topic

• Default = Not enabled
• Minimum value = 10 minutes
• Maximum value = 31 days

Export message data to BigQuery

Enabling this property lets you create a BigQuery subscription that writes messages to an existing BigQuery table as they are received. You don't need to configure a separate subscriber client. For more information about BigQuery subscriptions, see BigQuery subscriptions.

Export message data to Cloud Storage

Enabling this property lets you create a Cloud Storage subscription that writes messages to an existing Cloud Storage table as they are received. You don't need to configure a separate subscriber client. For more information about Cloud Storage subscriptions, see Cloud Storage subscriptions.

Google-owned and Google-managed encryption key

Specifies that the topic is encrypted using Google-owned and Google-managed encryption keys. Pub/Sub encrypts messages with Google-owned and Google-managed encryption keys by default, so choosing this option maintains the default behavior. Google handles key management and rotation automatically, ensuring your messages are always protected with the strongest available encryption. This option requires no further configuration. For more information about Google-owned and Google-managed encryption keys, see Default encryption with Google-owned and Google-managed encryption keys.

Cloud KMS key

Specifies if the topic is encrypted with a customer-managed encryption key (CMEK). Pub/Sub encrypts messages with Google-owned and Google-managed encryption keys by default. If you specify this option, Pub/Sub uses the envelope encryption pattern with CMEK. In this approach, Cloud KMS does not encrypt the messages. Instead, Cloud KMS encrypts the Data Encryption Keys (DEKs) that Pub/Sub creates for each topic. Pub/Sub encrypts the messages using the newest DEK that was generated for the topic. Pub/Sub decrypts the messages shortly before they are delivered to subscribers. For more information about creating a key, see Configure message encryption.

Create a topic

Create a topic before you can publish or subscribe to it.

PUT https://pubsub.googleapis.com/v1/projects/PROJECT_ID/topics/TOPIC_ID
Authorization: Bearer ACCESS_TOKEN
    

{
 "name": "projects/PROJECT_ID/topics/TOPIC_ID"
}

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";
}

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;
    }
}

import (
	"context"
	"fmt"
	"io"

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

func create(w io.Writer, projectID, topicID string) error {
	// projectID := "my-project-id"
	// topicID := "my-topic"
	ctx := context.Background()
	client, err := pubsub.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("pubsub.NewClient: %w", err)
	}
	defer client.Close()

	t, err := client.CreateTopic(ctx, topicID)
	if err != nil {
		return fmt.Errorf("CreateTopic: %w", err)
	}
	fmt.Fprintf(w, "Topic created: %v\n", t)
	return nil
}

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());
    }
  }
}

/**
 * TODO(developer): Uncomment this variable before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';

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

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

async function createTopic(topicNameOrId) {
  // Creates a new topic
  await pubSubClient.createTopic(topicNameOrId);
  console.log(`Topic ${topicNameOrId} created.`);
}

/**
 * TODO(developer): Uncomment this variable before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';

// Imports the Google Cloud client library
import {PubSub} from '@google-cloud/pubsub';

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

async function createTopic(topicNameOrId: string) {
  // Creates a new topic
  await pubSubClient.createTopic(topicNameOrId);
  console.log(`Topic ${topicNameOrId} created.`);
}

use Google\Cloud\PubSub\PubSubClient;

/**
 * Creates a Pub/Sub topic.
 *
 * @param string $projectId  The Google project ID.
 * @param string $topicName  The Pub/Sub topic name.
 */
function create_topic($projectId, $topicName)
{
    $pubsub = new PubSubClient([
        'projectId' => $projectId,
    ]);
    $topic = $pubsub->createTopic($topicName);

    printf('Topic created: %s' . PHP_EOL, $topic->name());
}

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}")

# topic_id = "your-topic-id"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.create_topic topic_id

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

Organization policy constraints

Organizational policies can restrict topic creation, for example, a policy can restrict message storage in a Compute Engine region. To avoid topic creation errors, examine and update organizational policies, as needed, before creating a topic.

If your project is newly created, wait a few minutes for the organization policy to initialize before creating a topic.

Go to Organization Policies

For more information, see Configure message storage policies.

What's next

• Choose the type of subscription for your topic.

• Learn how to publish a message to a topic.

• Create or modify a topic with gcloud CLI, REST APIs, or Client libraries.