Publish quickstart

A quickstart example for publishing messages to a topic.

Explore further

For detailed documentation that includes this code sample, see the following:

Publish and receive messages in Pub/Sub by using a client library

Code sample

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  #include 
  
 "google/cloud/pubsub/publisher.h" 
 #include <iostream> 
 int 
  
 main 
 ( 
 int 
  
 argc 
 , 
  
 char 
 * 
  
 argv 
 []) 
  
 try 
  
 { 
  
 if 
  
 ( 
 argc 
  
 != 
  
 3 
 ) 
  
 { 
  
 std 
 :: 
 cerr 
 << 
 "Usage: " 
 << 
 argv 
 [ 
 0 
 ] 
 << 
 " <project-id> <topic-id> 
 \n 
 " 
 ; 
  
 return 
  
 1 
 ; 
  
 } 
  
 std 
 :: 
 string 
  
 const 
  
 project_id 
  
 = 
  
 argv 
 [ 
 1 
 ]; 
  
 std 
 :: 
 string 
  
 const 
  
 topic_id 
  
 = 
  
 argv 
 [ 
 2 
 ]; 
  
 // Create a namespace alias to make the code easier to read. 
  
 namespace 
  
 pubsub 
  
 = 
  
 :: 
 google 
 :: 
 cloud 
 :: 
 pubsub 
 ; 
  
 auto 
  
 publisher 
  
 = 
  
 pubsub 
 :: 
 Publisher 
 ( 
  
 pubsub 
 :: 
 MakePublisherConnection 
 ( 
 pubsub 
 :: 
 Topic 
 ( 
 project_id 
 , 
  
 topic_id 
 ))); 
  
 auto 
  
 id 
  
 = 
  
 publisher 
  
 . 
 Publish 
 ( 
 pubsub 
 :: 
 MessageBuilder 
 {}. 
 SetData 
 ( 
 "Hello World!" 
 ). 
 Build 
 ()) 
  
 . 
 get 
 (); 
  
 if 
  
 ( 
 ! 
 id 
 ) 
  
 throw 
  
 std 
 :: 
 move 
 ( 
 id 
 ). 
 status 
 (); 
  
 std 
 :: 
 cout 
 << 
 "Hello World published with id=" 
 << 
 * 
 id 
 << 
 " 
 \n 
 " 
 ; 
  
 return 
  
 0 
 ; 
 } 
  
 catch 
  
 ( 
 google 
 :: 
 cloud 
 :: 
 Status 
  
 const 
&  
 status 
 ) 
  
 { 
  
 std 
 :: 
 cerr 
 << 
 "google::cloud::Status thrown: " 
 << 
 status 
 << 
 " 
 \n 
 " 
 ; 
  
 return 
  
 1 
 ; 
 }

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  using 
  
  Google.Cloud.PubSub.V1 
 
 ; 
 using 
  
 System 
 ; 
 using 
  
 System.Collections.Generic 
 ; 
 using 
  
 System.Linq 
 ; 
 using 
  
 System.Threading 
 ; 
 using 
  
 System.Threading.Tasks 
 ; 
 public 
  
 class 
  
 PublishMessagesAsyncSample 
 { 
  
 public 
  
 async 
  
 Task<int> 
  
 PublishMessagesAsync 
 ( 
 string 
  
 projectId 
 , 
  
 string 
  
 topicId 
 , 
  
 IEnumerable<string> 
  
 messageTexts 
 ) 
  
 { 
  
  TopicName 
 
  
 topicName 
  
 = 
  
  TopicName 
 
 . 
  FromProjectTopic 
 
 ( 
 projectId 
 , 
  
 topicId 
 ); 
  
  PublisherClient 
 
  
 publisher 
  
 = 
  
 await 
  
  PublisherClient 
 
 . 
  CreateAsync 
 
 ( 
 topicName 
 ); 
  
 int 
  
 publishedMessageCount 
  
 = 
  
 0 
 ; 
  
 var 
  
 publishTasks 
  
 = 
  
 messageTexts 
 . 
 Select 
 ( 
 async 
  
 text 
  
 = 
>  
 { 
  
 try 
  
 { 
  
 string 
  
 message 
  
 = 
  
 await 
  
 publisher 
 . 
 PublishAsync 
 ( 
 text 
 ); 
  
 Console 
 . 
 WriteLine 
 ( 
 $"Published message {message}" 
 ); 
  
 Interlocked 
 . 
 Increment 
 ( 
 ref 
  
 publishedMessageCount 
 ); 
  
 } 
  
 catch 
  
 ( 
 Exception 
  
 exception 
 ) 
  
 { 
  
 Console 
 . 
 WriteLine 
 ( 
 $"An error occurred when publishing message {text}: {exception.Message}" 
 ); 
  
 } 
  
 }); 
  
 await 
  
 Task 
 . 
 WhenAll 
 ( 
 publishTasks 
 ); 
  
 // PublisherClient instance should be shutdown after use. 
  
 // The TimeSpan specifies for how long to attempt to publish locally queued messages. 
  
 await 
  
 publisher 
 . 
  ShutdownAsync 
 
 ( 
 TimeSpan 
 . 
 FromSeconds 
 ( 
 15 
 )); 
  
 return 
  
 publishedMessageCount 
 ; 
  
 } 
 }

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  import 
  
 ( 
  
 "context" 
  
 "fmt" 
  
 "io" 
  
 "cloud.google.com/go/pubsub/v2" 
 ) 
 func 
  
 publish 
 ( 
 w 
  
 io 
 . 
 Writer 
 , 
  
 projectID 
 , 
  
 topicID 
 , 
  
 msg 
  
 string 
 ) 
  
 error 
  
 { 
  
 // projectID := "my-project-id" 
  
 // topicID := "my-topic" 
  
 // msg := "Hello World" 
  
 ctx 
  
 := 
  
 context 
 . 
 Background 
 () 
  
 client 
 , 
  
 err 
  
 := 
  
 pubsub 
 . 
 NewClient 
 ( 
 ctx 
 , 
  
 projectID 
 ) 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 return 
  
 fmt 
 . 
 Errorf 
 ( 
 "pubsub: NewClient: %w" 
 , 
  
 err 
 ) 
  
 } 
  
 defer 
  
 client 
 . 
 Close 
 () 
  
 // client.Publisher can be passed a topic ID (e.g. "my-topic") or 
  
 // a fully qualified name (e.g. "projects/my-project/topics/my-topic"). 
  
 // If a topic ID is provided, the project ID from the client is used. 
  
 // Reuse this publisher for all publish calls to send messages in batches. 
  
 publisher 
  
 := 
  
 client 
 . 
 Publisher 
 ( 
 topicID 
 ) 
  
 result 
  
 := 
  
 publisher 
 . 
 Publish 
 ( 
 ctx 
 , 
  
& pubsub 
 . 
 Message 
 { 
  
 Data 
 : 
  
 [] 
 byte 
 ( 
 msg 
 ), 
  
 }) 
  
 // Block until the result is returned and a server-generated 
  
 // ID is returned for the published message. 
  
 id 
 , 
  
 err 
  
 := 
  
 result 
 . 
 Get 
 ( 
 ctx 
 ) 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 return 
  
 fmt 
 . 
 Errorf 
 ( 
 "pubsub: result.Get: %w" 
 , 
  
 err 
 ) 
  
 } 
  
 fmt 
 . 
 Fprintf 
 ( 
 w 
 , 
  
 "Published a message; msg ID: %v\n" 
 , 
  
 id 
 ) 
  
 return 
  
 nil 
 }

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  import 
  
 com.google.api.core. ApiFuture 
 
 ; 
 import 
  
 com.google.cloud.pubsub.v1. Publisher 
 
 ; 
 import 
  
 com.google.protobuf. ByteString 
 
 ; 
 import 
  
 com.google.pubsub.v1. PubsubMessage 
 
 ; 
 import 
  
 com.google.pubsub.v1. TopicName 
 
 ; 
 import 
  
 java.io.IOException 
 ; 
 import 
  
 java.util.concurrent.ExecutionException 
 ; 
 import 
  
 java.util.concurrent.TimeUnit 
 ; 
 public 
  
 class 
 PublisherExample 
  
 { 
  
 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" 
 ; 
  
 publisherExample 
 ( 
 projectId 
 , 
  
 topicId 
 ); 
  
 } 
  
 public 
  
 static 
  
 void 
  
 publisherExample 
 ( 
 String 
  
 projectId 
 , 
  
 String 
  
 topicId 
 ) 
  
 throws 
  
 IOException 
 , 
  
 ExecutionException 
 , 
  
 InterruptedException 
  
 { 
  
  TopicName 
 
  
 topicName 
  
 = 
  
  TopicName 
 
 . 
 of 
 ( 
 projectId 
 , 
  
 topicId 
 ); 
  
  Publisher 
 
  
 publisher 
  
 = 
  
 null 
 ; 
  
 try 
  
 { 
  
 // Create a publisher instance with default settings bound to the topic 
  
 publisher 
  
 = 
  
  Publisher 
 
 . 
 newBuilder 
 ( 
 topicName 
 ). 
 build 
 (); 
  
 String 
  
 message 
  
 = 
  
 "Hello World!" 
 ; 
  
  ByteString 
 
  
 data 
  
 = 
  
  ByteString 
 
 . 
  copyFromUtf8 
 
 ( 
 message 
 ); 
  
  PubsubMessage 
 
  
 pubsubMessage 
  
 = 
  
  PubsubMessage 
 
 . 
 newBuilder 
 (). 
  setData 
 
 ( 
 data 
 ). 
 build 
 (); 
  
 // Once published, returns a server-assigned message id (unique within the topic) 
  
 ApiFuture<String> 
  
 messageIdFuture 
  
 = 
  
  publish 
 
er . 
  publish 
 
 ( 
 pubsubMessage 
 ); 
  
 String 
  
 messageId 
  
 = 
  
 messageIdFuture 
 . 
 get 
 (); 
  
 System 
 . 
 out 
 . 
 println 
 ( 
 "Published message ID: " 
  
 + 
  
 messageId 
 ); 
  
 } 
  
 finally 
  
 { 
  
 if 
  
 ( 
 publisher 
  
 != 
  
 null 
 ) 
  
 { 
  
 // When finished with the publisher, shutdown to free up resources. 
  
 publisher 
 . 
  shutdown 
 
 (); 
  
 publisher 
 . 
  awaitTermination 
 
 ( 
 1 
 , 
  
 TimeUnit 
 . 
 MINUTES 
 ); 
  
 } 
  
 } 
  
 } 
 }

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  /** 
  
 * 
  
 TODO 
 ( 
 developer 
 ): 
  
 Uncomment 
  
 these 
  
 variables 
  
 before 
  
 running 
  
 the 
  
 sample 
 . 
  
 */ 
 // 
  
 const 
  
 topicNameOrId 
  
 = 
  
 'YOUR_TOPIC_NAME_OR_ID' 
 ; 
 // 
  
 const 
  
 data 
  
 = 
  
 JSON 
 . 
 stringify 
 ({ 
 foo 
 : 
  
 'bar' 
 }); 
 // 
  
 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 
  
 publishMessage 
 ( 
 topicNameOrId 
 , 
  
 data 
 ) 
  
 { 
  
 // 
  
 Publishes 
  
 the 
  
 message 
  
 as 
  
 a 
  
 string 
 , 
  
 e 
 . 
 g 
 . 
  
 "Hello, world!" 
  
 or 
  
 JSON 
 . 
 stringify 
 ( 
 someObject 
 ) 
  
 const 
  
 dataBuffer 
  
 = 
  
 Buffer 
 . 
 from 
 ( 
 data 
 ); 
  
 // 
  
 Cache 
  
 topic 
  
 objects 
  
 ( 
 publishers 
 ) 
  
 and 
  
 reuse 
  
 them 
 . 
  
 const 
  
 topic 
  
 = 
  
 pubSubClient 
 . 
 topic 
 ( 
 topicNameOrId 
 ); 
  
 try 
  
 { 
  
 const 
  
 messageId 
  
 = 
  
 await 
  
 topic 
 . 
 publishMessage 
 ({ 
 data 
 : 
  
 dataBuffer 
 }); 
  
 console 
 . 
 log 
 ( 
 ` 
 Message 
  
 $ 
 { 
 messageId 
 } 
  
 published 
 . 
 ` 
 ); 
  
 } 
  
 catch 
  
 ( 
 error 
 ) 
  
 { 
  
 console 
 . 
 error 
 ( 
 ` 
 Received 
  
 error 
  
 while 
  
 publishing 
 : 
  
 $ 
 { 
 error 
 . 
 message 
 } 
 ` 
 ); 
  
 process 
 . 
 exitCode 
  
 = 
  
 1 
 ; 
  
 } 
 }

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  /** 
 * 
 TODO 
 ( 
 developer 
 ): 
 Uncomment 
 these 
 variables 
 before 
 running 
 the 
 sample 
 . 
 */ 
 // 
 const 
 topicNameOrId 
 = 
 'YOUR_TOPIC_NAME_OR_ID' 
 ; 
 // 
 const 
 data 
 = 
 JSON 
 . 
 stringify 
 ({ 
 foo 
 : 
 'bar' 
 }); 
 // 
 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 
 publishMessage 
 ( 
 topicNameOrId 
 : 
 string 
 , 
 data 
 : 
 string 
 ) 
 { 
 // 
 Publishes 
 the 
 message 
 as 
 a 
 string 
 , 
 e 
 . 
 g 
 . 
 "Hello, world!" 
 or 
 JSON 
 . 
 stringify 
 ( 
 someObject 
 ) 
 const 
 dataBuffer 
 = 
 Buffer 
 . 
 from 
 ( 
 data 
 ); 
 // 
 Cache 
 topic 
 objects 
 ( 
 publishers 
 ) 
 and 
 reuse 
 them 
 . 
 const 
 topic 
 = 
 pubSubClient 
 . 
 topic 
 ( 
 topicNameOrId 
 ); 
 try 
 { 
 const 
 messageId 
 = 
 await 
 topic 
 . 
 publishMessage 
 ({ 
 data 
 : 
 dataBuffer 
 }); 
 console 
 . 
 log 
 ( 
 ` 
 Message 
 $ 
 { 
 messageId 
 } 
 published 
 . 
 ` 
 ); 
 } 
 catch 
 ( 
 error 
 ) 
 { 
 console 
 . 
 error 
 ( 
 ` 
 Received 
 error 
 while 
 publishing 
 : 
 $ 
 {( 
 error 
 as 
 Error 
 ) 
 . 
 message 
 } 
 ` 
 , 
 ); 
 process 
 . 
 exitCode 
 = 
 1 
 ; 
 } 
 }

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  use Google\Cloud\PubSub\MessageBuilder; 
 use Google\Cloud\PubSub\PubSubClient; 
 /** 
 * Publishes a message for a Pub/Sub topic. 
 * 
 * @param string $projectId  The Google project ID. 
 * @param string $topicName  The Pub/Sub topic name. 
 * @param string $message  The message to publish. 
 */ 
 function publish_message($projectId, $topicName, $message) 
 { 
 $pubsub = new PubSubClient([ 
 'projectId' => $projectId, 
 ]); 
 $topic = $pubsub->topic($topicName); 
 $topic->publish((new MessageBuilder)->setData($message)->build()); 
 print('Message published' . PHP_EOL); 
 }

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  from 
  
 google.cloud 
  
 import 
 pubsub_v1 
 # TODO(developer) 
 # project_id = "your-project-id" 
 # topic_id = "your-topic-id" 
 publisher 
 = 
 pubsub_v1 
 . 
  PublisherClient 
 
 () 
 # The `topic_path` method creates a fully qualified identifier 
 # in the form `projects/{project_id}/topics/{topic_id}` 
 topic_path 
 = 
 publisher 
 . 
 topic_path 
 ( 
 project_id 
 , 
 topic_id 
 ) 
 for 
 n 
 in 
 range 
 ( 
 1 
 , 
 10 
 ): 
 data_str 
 = 
 f 
 "Message number 
 { 
 n 
 } 
 " 
 # Data must be a bytestring 
 data 
 = 
 data_str 
 . 
 encode 
 ( 
 "utf-8" 
 ) 
 # When you publish a message, the client returns a future. 
 future 
 = 
  publish 
 
er . 
  publish 
 
 ( 
 topic_path 
 , 
 data 
 ) 
 print 
 ( 
 future 
 . 
 result 
 ()) 
 print 
 ( 
 f 
 "Published messages to 
 { 
 topic_path 
 } 
 ." 
 )

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 .

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  # topic_id = "your-topic-id" 
 pubsub 
  
 = 
  
 Google 
 :: 
 Cloud 
 :: 
  PubSub 
 
 . 
  new 
 
 publisher 
  
 = 
  
 pubsub 
 . 
  publisher 
 
  
 topic_id 
 publisher 
 . 
 publish 
  
 "This is a test message." 
 puts 
  
 "Message published."

What's next

To search and filter code samples for other Google Cloud products, see the Google Cloud sample browser .

Publish quickstart Stay organized with collections Save and categorize content based on your preferences.

Explore further

Code sample

C++

C#

Go

Java

Node.js

Node.js

PHP

Python

Ruby

What's next

Publish quickstart