List topics

This document describes how to list a Pub/Sub topic. To list a topic you can use the Google Cloud console, the gcloud CLI, the client library, or the Pub/Sub API.

Before you begin

Learn about topics and the publish messages workflow.
Create a topic .

Required roles and permissions

To get the permissions that you need to list topics and manage them, 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 list topics and manage them. To see the exact permissions that are required, expand the Required permissionssection:

Required permissions

The following permissions are required to list topics and manage them:

Create a topic: pubsub.topics.create
Delete a topic: pubsub.topics.delete
Detach a subscription from a topic: pubsub.topics.detachSubscription
Get a topic: pubsub.topics.get
List a topic: pubsub.topics.list
Publish to a topic: pubsub.topics.publish
Update a topic: pubsub.topics.update
Get the IAM policy for a topic: pubsub.topics.getIamPolicy
Configure the IAM policy for a topic: pubsub.topics.setIamPolicy

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.

List a topic

Console

In the Google Cloud console, go to the Pub/Sub Topics page.

Go to Topics

The Topics page lists all the available topics.

By default, the console returns 50 topics. You can increase this value to return a maximum of 200 topics by using the Rows per pagedrop down toggle. This toggle only appears in the console if you have more than 20 topics in a project.

gcloud

In the Google Cloud console, activate Cloud Shell.

Activate Cloud Shell

At the bottom of the Google Cloud console, a Cloud Shell session starts and displays a command-line prompt. Cloud Shell is a shell environment with the Google Cloud CLI already installed and with values already set for your current project. It can take a few seconds for the session to initialize.
To list topics, use the gcloud pubsub topics list command:
```
gcloud  
pubsub  
topics  
list
```

By default, a maximum of 100 results are returned per query. You can specify an alternative value of up to 1,000 using the page size parameter. For example, using the Google Cloud CLI, specify --page-size=1000 .

REST

To list topics, use the projects.topics.list method:

Request:

The request must be authenticated with an access token in the Authorization header. To obtain an access token for the current Application Default Credentials: gcloud auth application-default print-access-token .

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

Where:

PROJECT_ID is your project ID.

Response:

{
"topics": [
  {
    "name": "projects/ PROJECT_ID 
/topics/mytopic1", ... 
 }, 
 { 
 "name": "projects/ PROJECT_ID 
/topics/mytopic2", 
 ... 
 } 
]
}

C++

Before trying this sample, follow the C++ setup instructions in Quickstart: Using Client Libraries . For more information, see the Pub/Sub C++ API reference documentation .

  namespace 
  
 pubsub_admin 
  
 = 
  
 :: 
 google 
 :: 
 cloud 
 :: 
 pubsub_admin 
 ; 
 []( 
 pubsub_admin 
 :: 
 TopicAdminClient 
  
 client 
 , 
  
 std 
 :: 
 string 
  
 const 
&  
 project_id 
 ) 
  
 { 
  
 int 
  
 count 
  
 = 
  
 0 
 ; 
  
 for 
  
 ( 
 auto 
&  
 topic 
  
 : 
  
 client 
 . 
 ListTopics 
 ( 
 "projects/" 
  
 + 
  
 project_id 
 )) 
  
 { 
  
 if 
  
 ( 
 ! 
 topic 
 ) 
  
 throw 
  
 std 
 :: 
 move 
 ( 
 topic 
 ). 
 status 
 (); 
  
 std 
 :: 
 cout 
 << 
 "Topic Name: " 
 << 
 topic 
 - 
> name 
 () 
 << 
 " 
 \n 
 " 
 ; 
  
 ++ 
 count 
 ; 
  
 } 
  
 if 
  
 ( 
 count 
  
 == 
  
 0 
 ) 
  
 { 
  
 std 
 :: 
 cout 
 << 
 "No topics found in project " 
 << 
 project_id 
 << 
 " 
 \n 
 " 
 ; 
  
 } 
 }

C#

Before trying this sample, follow the C# setup instructions in Quickstart: Using Client Libraries . For more information, see the Pub/Sub C# API reference documentation .

  using 
  
  Google.Api.Gax.ResourceNames 
 
 ; 
 using 
  
  Google.Cloud.PubSub.V1 
 
 ; 
 using 
  
 System.Collections.Generic 
 ; 
 public 
  
 class 
  
 ListProjectTopicsSample 
 { 
  
 public 
  
 IEnumerable<Topic> 
  
 ListProjectTopics 
 ( 
 string 
  
 projectId 
 ) 
  
 { 
  
  PublisherServiceApiClient 
 
  
 publisher 
  
 = 
  
  PublisherServiceApiClient 
 
 . 
  Create 
 
 (); 
  
  ProjectName 
 
  
 projectName 
  
 = 
  
  ProjectName 
 
 . 
  FromProject 
 
 ( 
 projectId 
 ); 
  
 IEnumerable<Topic> 
  
 topics 
  
 = 
  
 publisher 
 . 
  ListTopics 
 
 ( 
 projectName 
 ); 
  
 return 
  
 topics 
 ; 
  
 } 
 }

Go

The following sample uses the major version of the Go Pub/Sub client library (v2). If you are still using the v1 library, see the migration guide to v2 . To see a list of v1 code samples, see the deprecated code samples .

Before trying this sample, follow the Go setup instructions in Quickstart: Using Client Libraries . For more information, see the Pub/Sub Go API reference documentation .

  import 
  
 ( 
  
 "context" 
  
 "fmt" 
  
 "io" 
  
 "cloud.google.com/go/pubsub/v2" 
  
 "cloud.google.com/go/pubsub/v2/apiv1/pubsubpb" 
  
 "google.golang.org/api/iterator" 
 ) 
 func 
  
 listTopics 
 ( 
 w 
  
 io 
 . 
 Writer 
 , 
  
 projectID 
  
 string 
 ) 
  
 error 
  
 { 
  
 // projectID := "my-project-id" 
  
 ctx 
  
 := 
  
 context 
 . 
 Background 
 () 
  
 client 
 , 
  
 err 
  
 := 
  
 pubsub 
 . 
 NewClient 
 ( 
 ctx 
 , 
  
 projectID 
 ) 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 return 
  
 fmt 
 . 
 Errorf 
 ( 
 "pubsub.NewClient: %w" 
 , 
  
 err 
 ) 
  
 } 
  
 defer 
  
 client 
 . 
 Close 
 () 
  
 req 
  
 := 
  
& pubsubpb 
 . 
 ListTopicsRequest 
 { 
  
 Project 
 : 
  
 fmt 
 . 
 Sprintf 
 ( 
 "projects/%s" 
 , 
  
 projectID 
 ), 
  
 } 
  
 it 
  
 := 
  
 client 
 . 
 TopicAdminClient 
 . 
 ListTopics 
 ( 
 ctx 
 , 
  
 req 
 ) 
  
 for 
  
 { 
  
 topic 
 , 
  
 err 
  
 := 
  
 it 
 . 
 Next 
 () 
  
 if 
  
 err 
  
 == 
  
 iterator 
 . 
 Done 
  
 { 
  
 break 
  
 } 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 return 
  
 fmt 
 . 
 Errorf 
 ( 
 "error listing topics: %w" 
 , 
  
 err 
 ) 
  
 } 
  
 fmt 
 . 
 Fprintf 
 ( 
 w 
 , 
  
 "got topic: %s\n" 
 , 
  
 topic 
 ) 
  
 } 
  
 return 
  
 nil 
 }

Java

Before trying this sample, follow the Java setup instructions in 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. ProjectName 
 
 ; 
 import 
  
 com.google.pubsub.v1. Topic 
 
 ; 
 import 
  
 java.io.IOException 
 ; 
 public 
  
 class 
 ListTopicsExample 
  
 { 
  
 public 
  
 static 
  
 void 
  
 main 
 ( 
 String 
 ... 
  
 args 
 ) 
  
 throws 
  
 Exception 
  
 { 
  
 // TODO(developer): Replace these variables before running the sample. 
  
 String 
  
 projectId 
  
 = 
  
 "your-project-id" 
 ; 
  
 listTopicsExample 
 ( 
 projectId 
 ); 
  
 } 
  
 public 
  
 static 
  
 void 
  
 listTopicsExample 
 ( 
 String 
  
 projectId 
 ) 
  
 throws 
  
 IOException 
  
 { 
  
 try 
  
 ( 
  TopicAdminClient 
 
  
 topicAdminClient 
  
 = 
  
  TopicAdminClient 
 
 . 
 create 
 ()) 
  
 { 
  
  ProjectName 
 
  
 projectName 
  
 = 
  
  ProjectName 
 
 . 
 of 
 ( 
 projectId 
 ); 
  
 for 
  
 ( 
  Topic 
 
  
 topic 
  
 : 
  
 topicAdminClient 
 . 
 listTopics 
 ( 
 projectName 
 ). 
 iterateAll 
 ()) 
  
 { 
  
 System 
 . 
 out 
 . 
 println 
 ( 
 topic 
 . 
 getName 
 ()); 
  
 } 
  
 System 
 . 
 out 
 . 
 println 
 ( 
 "Listed all topics." 
 ); 
  
 } 
  
 } 
 }

Node.js

Before trying this sample, follow the Node.js setup instructions in 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' 
 ); 
 // 
  
 Creates 
  
 a 
  
 client 
 ; 
  
 cache 
  
 this 
  
 for 
  
 further 
  
 use 
 const 
  
 pubSubClient 
  
 = 
  
 new 
  
 PubSub 
 (); 
 async 
  
 function 
  
 listAllTopics 
 () 
  
 { 
  
 // 
  
 Lists 
  
 all 
  
 topics 
  
 in 
  
 the 
  
 current 
  
 project 
  
 const 
  
 [ 
 topics 
 ] 
  
 = 
  
 await 
  
 pubSubClient 
 . 
 getTopics 
 (); 
  
 console 
 . 
 log 
 ( 
 'Topics:' 
 ); 
  
 topics 
 . 
 forEach 
 ( 
 topic 
  
 = 
>  
 console 
 . 
 log 
 ( 
 topic 
 . 
 name 
 )); 
 }

Node.ts

Before trying this sample, follow the Node.js setup instructions in Quickstart: Using Client Libraries . For more information, see the Pub/Sub Node.js API reference documentation .

  // 
 Imports 
 the 
 Google 
 Cloud 
 client 
 library 
 import 
  
 { 
 PubSub 
 , 
 Topic 
 } 
 from 
  
 '@google-cloud/pubsub' 
 ; 
 // 
 Creates 
 a 
 client 
 ; 
 cache 
 this 
 for 
 further 
 use 
 const 
 pubSubClient 
 = 
 new 
 PubSub 
 (); 
 async 
 function 
 listAllTopics 
 () 
 { 
 // 
 Lists 
 all 
 topics 
 in 
 the 
 current 
 project 
 const 
 [ 
 topics 
 ] 
 = 
 await 
 pubSubClient 
 . 
 getTopics 
 (); 
 console 
 . 
 log 
 ( 
 'Topics:' 
 ); 
 topics 
 . 
 forEach 
 (( 
 topic 
 : 
 Topic 
 ) 
 = 
> console 
 . 
 log 
 ( 
 topic 
 . 
 name 
 )); 
 }

PHP

Before trying this sample, follow the PHP setup instructions in Quickstart: Using Client Libraries . For more information, see the Pub/Sub PHP API reference documentation .

  use Google\Cloud\PubSub\PubSubClient; 
 /** 
 * Lists all Pub/Sub topics. 
 * 
 * @param string $projectId  The Google project ID. 
 */ 
 function list_topics($projectId) 
 { 
 $pubsub = new PubSubClient([ 
 'projectId' => $projectId, 
 ]); 
 foreach ($pubsub->topics() as $topic) { 
 printf('Topic: %s' . PHP_EOL, $topic->name()); 
 } 
 }

Python

Before trying this sample, follow the Python setup instructions in 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" 
 publisher 
 = 
 pubsub_v1 
 . 
  PublisherClient 
 
 () 
 project_path 
 = 
 f 
 "projects/ 
 { 
 project_id 
 } 
 " 
 for 
 topic 
 in 
 publisher 
 . 
 list_topics 
 ( 
 request 
 = 
 { 
 "project" 
 : 
 project_path 
 }): 
 print 
 ( 
 topic 
 )

Ruby

The following sample uses Ruby Pub/Sub client library v3. If you are still using the v2 library, see the migration guide to v3 . To see a list of Ruby v2 code samples, see the deprecated code samples .

Before trying this sample, follow the Ruby setup instructions in Quickstart: Using Client Libraries . For more information, see the Pub/Sub Ruby API reference documentation .

  pubsub 
  
 = 
  
 Google 
 :: 
 Cloud 
 :: 
  PubSub 
 
 . 
  new 
 
 topic_admin 
  
 = 
  
 pubsub 
 . 
  topic_admin 
 
 topics 
  
 = 
  
 topic_admin 
 . 
 list_topics 
  
 project 
 : 
  
 pubsub 
 . 
 project_path 
 puts 
  
 "Topics in project:" 
 topics 
 . 
 each 
  
 do 
  
 | 
 topic 
 | 
  
 puts 
  
 topic 
 . 
 name 
 end

What's next

Choose the type of subscription for your topic.
Create a subscription for your topic: pull , push , or BigQuery .
Create or modify a topic with gcloud CLI .
Create or modify a topic with REST APIs .

List topics Stay organized with collections Save and categorize content based on your preferences.