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    Publish with ordering keys

    Publishes messages with an ordering key.

    Explore further

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

    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 .

      namespace 
  
 pubsub 
  
 = 
  
 :: 
 google 
 :: 
 cloud 
 :: 
 pubsub 
 ; 
 using 
  
 :: 
 google 
 :: 
 cloud 
 :: 
 future 
 ; 
 using 
  
 :: 
 google 
 :: 
 cloud 
 :: 
 StatusOr 
 ; 
 []( 
 pubsub 
 :: 
 Publisher 
  
 publisher 
 ) 
  
 { 
  
 struct 
  
 SampleData 
  
 { 
  
 std 
 :: 
 string 
  
 ordering_key 
 ; 
  
 std 
 :: 
 string 
  
 data 
 ; 
  
 } 
  
 data 
 [] 
  
 = 
  
 { 
  
 { 
 "key1" 
 , 
  
 "message1" 
 }, 
  
 { 
 "key2" 
 , 
  
 "message2" 
 }, 
  
 { 
 "key1" 
 , 
  
 "message3" 
 }, 
  
 { 
 "key1" 
 , 
  
 "message4" 
 }, 
  
 { 
 "key1" 
 , 
  
 "message5" 
 }, 
  
 }; 
  
 std 
 :: 
 vector<future<void> 
>  
 done 
 ; 
  
 for 
  
 ( 
 auto 
&  
 datum 
  
 : 
  
 data 
 ) 
  
 { 
  
 auto 
  
 message_id 
  
 = 
  
 publisher 
 . 
 Publish 
 ( 
 pubsub 
 :: 
 MessageBuilder 
 {} 
  
 . 
 SetData 
 ( 
 "Hello World! [" 
  
 + 
  
 datum 
 . 
 data 
  
 + 
  
 "]" 
 ) 
  
 . 
 SetOrderingKey 
 ( 
 datum 
 . 
 ordering_key 
 ) 
  
 . 
 Build 
 ()); 
  
 std 
 :: 
 string 
  
 ack_id 
  
 = 
  
 datum 
 . 
 ordering_key 
  
 + 
  
 "#" 
  
 + 
  
 datum 
 . 
 data 
 ; 
  
 done 
 . 
 push_back 
 ( 
 message_id 
 . 
 then 
 ([ 
 ack_id 
 ]( 
 future<StatusOr<std 
 :: 
 string 
>>  
 f 
 ) 
  
 { 
  
 auto 
  
 id 
  
 = 
  
 f 
 . 
 get 
 (); 
  
 if 
  
 ( 
 ! 
 id 
 ) 
  
 throw 
  
 std 
 :: 
 move 
 ( 
 id 
 ). 
 status 
 (); 
  
 std 
 :: 
 cout 
 << 
 "Message " 
 << 
 ack_id 
 << 
 " published with id=" 
 << 
 * 
 id 
 << 
 " 
 \n 
 " 
 ; 
  
 })); 
  
 } 
  
 publisher 
 . 
 Flush 
 (); 
  
 // Block until all the messages are published (optional) 
  
 for 
  
 ( 
 auto 
&  
 f 
  
 : 
  
 done 
 ) 
  
 f 
 . 
 get 
 (); 
 }

    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 
  
 PublishOrderedMessagesAsyncSample 
 { 
  
 public 
  
 async 
  
 Task<int> 
  
 PublishOrderedMessagesAsync 
 ( 
 string 
  
 projectId 
 , 
  
 string 
  
 topicId 
 , 
  
 IEnumerable 
< ( 
 string 
 , 
  
 string 
 ) 
>  
 keysAndMessages 
 ) 
  
 { 
  
  TopicName 
 
  
 topicName 
  
 = 
  
  TopicName 
 
 . 
  FromProjectTopic 
 
 ( 
 projectId 
 , 
  
 topicId 
 ); 
  
 var 
  
 customSettings 
  
 = 
  
 new 
  
 PublisherClient 
 . 
 Settings 
  
 { 
  
 EnableMessageOrdering 
  
 = 
  
 true 
  
 }; 
  
  PublisherClient 
 
  
 publisher 
  
 = 
  
 await 
  
 new 
  
  PublisherClientBuilder 
 
  
 { 
  
 TopicName 
  
 = 
  
 topicName 
 , 
  
 // Sending messages to the same region ensures they are received in order even when multiple publishers are used. 
  
 Endpoint 
  
 = 
  
 "us-east1-pubsub.googleapis.com:443" 
 , 
  
 Settings 
  
 = 
  
 customSettings 
  
 }. 
 BuildAsync 
 (); 
  
 int 
  
 publishedMessageCount 
  
 = 
  
 0 
 ; 
  
 var 
  
 publishTasks 
  
 = 
  
 keysAndMessages 
 . 
 Select 
 ( 
 async 
  
 keyAndMessage 
  
 = 
>  
 { 
  
 try 
  
 { 
  
 string 
  
 message 
  
 = 
  
 await 
  
 publisher 
 . 
 PublishAsync 
 ( 
 keyAndMessage 
 . 
 Item1 
 , 
  
 keyAndMessage 
 . 
 Item2 
 ); 
  
 Console 
 . 
 WriteLine 
 ( 
 $"Published message {message}" 
 ); 
  
 Interlocked 
 . 
 Increment 
 ( 
 ref 
  
 publishedMessageCount 
 ); 
  
 } 
  
 catch 
  
 ( 
 Exception 
  
 exception 
 ) 
  
 { 
  
 Console 
 . 
 WriteLine 
 ( 
 $"An error occurred when publishing message {keyAndMessage.Item2}: {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" 
  
 "sync" 
  
 "sync/atomic" 
  
 "cloud.google.com/go/pubsub/v2" 
  
 "google.golang.org/api/option" 
 ) 
 func 
  
 publishWithOrderingKey 
 ( 
 w 
  
 io 
 . 
 Writer 
 , 
  
 projectID 
 , 
  
 topicID 
  
 string 
 ) 
  
 { 
  
 // projectID := "my-project-id" 
  
 // topicID := "my-topic" 
  
 ctx 
  
 := 
  
 context 
 . 
 Background 
 () 
  
 // Pub/Sub's ordered delivery guarantee only applies when publishes for an ordering key are in the same region. 
  
 // For list of locational endpoints for Pub/Sub, see https://cloud.google.com/pubsub/docs/reference/service_apis_overview#list_of_locational_endpoints 
  
 client 
 , 
  
 err 
  
 := 
  
 pubsub 
 . 
 NewClient 
 ( 
 ctx 
 , 
  
 projectID 
 , 
  
 option 
 . 
 WithEndpoint 
 ( 
 "us-east1-pubsub.googleapis.com:443" 
 )) 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 fmt 
 . 
 Fprintf 
 ( 
 w 
 , 
  
 "pubsub.NewClient: %v" 
 , 
  
 err 
 ) 
  
 return 
  
 } 
  
 defer 
  
 client 
 . 
 Close 
 () 
  
 var 
  
 wg 
  
 sync 
 . 
 WaitGroup 
  
 var 
  
 totalErrors 
  
 uint64 
  
 // 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 
 ) 
  
 publisher 
 . 
 EnableMessageOrdering 
  
 = 
  
 true 
  
 messages 
  
 := 
  
 [] 
 struct 
  
 { 
  
 message 
  
 string 
  
 orderingKey 
  
 string 
  
 }{ 
  
 { 
  
 message 
 : 
  
 "message1" 
 , 
  
 orderingKey 
 : 
  
 "key1" 
 , 
  
 }, 
  
 { 
  
 message 
 : 
  
 "message2" 
 , 
  
 orderingKey 
 : 
  
 "key2" 
 , 
  
 }, 
  
 { 
  
 message 
 : 
  
 "message3" 
 , 
  
 orderingKey 
 : 
  
 "key1" 
 , 
  
 }, 
  
 { 
  
 message 
 : 
  
 "message4" 
 , 
  
 orderingKey 
 : 
  
 "key2" 
 , 
  
 }, 
  
 } 
  
 for 
  
 _ 
 , 
  
 m 
  
 := 
  
 range 
  
 messages 
  
 { 
  
 result 
  
 := 
  
 publisher 
 . 
 Publish 
 ( 
 ctx 
 , 
  
& pubsub 
 . 
 Message 
 { 
  
 Data 
 : 
  
 [] 
 byte 
 ( 
 m 
 . 
 message 
 ), 
  
 OrderingKey 
 : 
  
 m 
 . 
 orderingKey 
 , 
  
 }) 
  
 wg 
 . 
 Add 
 ( 
 1 
 ) 
  
 go 
  
 func 
 ( 
 res 
  
 * 
 pubsub 
 . 
 PublishResult 
 ) 
  
 { 
  
 defer 
  
 wg 
 . 
 Done 
 () 
  
 // The Get method blocks until a server-generated ID or 
  
 // an error is returned for the published message. 
  
 _ 
 , 
  
 err 
  
 := 
  
 res 
 . 
 Get 
 ( 
 ctx 
 ) 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 // Error handling code can be added here. 
  
 fmt 
 . 
 Printf 
 ( 
 "Failed to publish: %s\n" 
 , 
  
 err 
 ) 
  
 atomic 
 . 
 AddUint64 
 ( 
& totalErrors 
 , 
  
 1 
 ) 
  
 return 
  
 } 
  
 }( 
 result 
 ) 
  
 } 
  
 wg 
 . 
 Wait 
 () 
  
 if 
  
 totalErrors 
 > 
 0 
  
 { 
  
 fmt 
 . 
 Fprintf 
 ( 
 w 
 , 
  
 "%d of 4 messages did not publish successfully" 
 , 
  
 totalErrors 
 ) 
  
 return 
  
 } 
  
 fmt 
 . 
 Fprint 
 ( 
 w 
 , 
  
 "Published 4 messages with ordering keys successfully\n" 
 ) 
 }

    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.api.core. ApiFutureCallback 
 
 ; 
 import 
  
 com.google.api.core. ApiFutures 
 
 ; 
 import 
  
 com.google.api.gax.rpc. ApiException 
 
 ; 
 import 
  
 com.google.cloud.pubsub.v1. Publisher 
 
 ; 
 import 
  
 com.google.common.util.concurrent.MoreExecutors 
 ; 
 import 
  
 com.google.protobuf. ByteString 
 
 ; 
 import 
  
 com.google.pubsub.v1. PubsubMessage 
 
 ; 
 import 
  
 com.google.pubsub.v1. TopicName 
 
 ; 
 import 
  
 java.io.IOException 
 ; 
 import 
  
 java.util.LinkedHashMap 
 ; 
 import 
  
 java.util.Map 
 ; 
 import 
  
 java.util.concurrent.TimeUnit 
 ; 
 public 
  
 class 
 PublishWithOrderingKeys 
  
 { 
  
 public 
  
 static 
  
 void 
  
 main 
 ( 
 String 
 ... 
  
 args 
 ) 
  
 throws 
  
 Exception 
  
 { 
  
 // TODO(developer): Replace these variables before running the sample. 
  
 String 
  
 projectId 
  
 = 
  
 "your-project-id" 
 ; 
  
 // Choose an existing topic. 
  
 String 
  
 topicId 
  
 = 
  
 "your-topic-id" 
 ; 
  
 publishWithOrderingKeysExample 
 ( 
 projectId 
 , 
  
 topicId 
 ); 
  
 } 
  
 public 
  
 static 
  
 void 
  
 publishWithOrderingKeysExample 
 ( 
 String 
  
 projectId 
 , 
  
 String 
  
 topicId 
 ) 
  
 throws 
  
 IOException 
 , 
  
 InterruptedException 
  
 { 
  
  TopicName 
 
  
 topicName 
  
 = 
  
  TopicName 
 
 . 
 of 
 ( 
 projectId 
 , 
  
 topicId 
 ); 
  
 // Create a publisher and set message ordering to true. 
  
  Publisher 
 
  
 publisher 
  
 = 
  
  Publisher 
 
 . 
 newBuilder 
 ( 
 topicName 
 ) 
  
 // Sending messages to the same region ensures they are received in order 
  
 // even when multiple publishers are used. 
  
 . 
 setEndpoint 
 ( 
 "us-east1-pubsub.googleapis.com:443" 
 ) 
  
 . 
 setEnableMessageOrdering 
 ( 
 true 
 ) 
  
 . 
 build 
 (); 
  
 try 
  
 { 
  
 Map<String 
 , 
  
 String 
>  
 messages 
  
 = 
  
 new 
  
 LinkedHashMap<String 
 , 
  
 String 
> (); 
  
 messages 
 . 
 put 
 ( 
 "message1" 
 , 
  
 "key1" 
 ); 
  
 messages 
 . 
 put 
 ( 
 "message2" 
 , 
  
 "key2" 
 ); 
  
 messages 
 . 
 put 
 ( 
 "message3" 
 , 
  
 "key1" 
 ); 
  
 messages 
 . 
 put 
 ( 
 "message4" 
 , 
  
 "key2" 
 ); 
  
 for 
  
 ( 
 Map 
 . 
 Entry<String 
 , 
  
 String 
>  
 entry 
  
 : 
  
 messages 
 . 
 entrySet 
 ()) 
  
 { 
  
 ByteString 
  
 data 
  
 = 
  
 ByteString 
 . 
 copyFromUtf8 
 ( 
 entry 
 . 
 getKey 
 ()); 
  
 PubsubMessage 
  
 pubsubMessage 
  
 = 
  
 PubsubMessage 
 . 
 newBuilder 
 (). 
 setData 
 ( 
 data 
 ). 
 setOrderingKey 
 ( 
 entry 
 . 
 getValue 
 ()). 
 build 
 (); 
  
 ApiFuture<String> 
  
 future 
  
 = 
  
 publisher 
 . 
 publish 
 ( 
 pubsubMessage 
 ); 
  
 // Add an asynchronous callback to handle publish success / failure. 
  
 ApiFutures 
 . 
 addCallback 
 ( 
  
 future 
 , 
  
 new 
  
 ApiFutureCallback<String> 
 () 
  
 { 
  
 @Override 
  
 public 
  
 void 
  
 onFailure 
 ( 
 Throwable 
  
 throwable 
 ) 
  
 { 
  
 if 
  
 ( 
 throwable 
  
 instanceof 
  
 ApiException 
 ) 
  
 { 
  
 ApiException 
  
 apiException 
  
 = 
  
 (( 
 ApiException 
 ) 
  
 throwable 
 ); 
  
 // Details on the API exception. 
  
 System 
 . 
 out 
 . 
 println 
 ( 
 apiException 
 . 
 getStatusCode 
 (). 
 getCode 
 ()); 
  
 System 
 . 
 out 
 . 
 println 
 ( 
 apiException 
 . 
 isRetryable 
 ()); 
  
 } 
  
 System 
 . 
 out 
 . 
 println 
 ( 
 "Error publishing message : " 
  
 + 
  
 pubsubMessage 
 . 
 getData 
 ()); 
  
 } 
  
 @Override 
  
 public 
  
 void 
  
 onSuccess 
 ( 
 String 
  
 messageId 
 ) 
  
 { 
  
 // Once published, returns server-assigned message ids (unique within the topic). 
  
 System 
 . 
 out 
 . 
 println 
 ( 
 pubsubMessage 
 . 
 getData 
 () 
  
 + 
  
 " : " 
  
 + 
  
 messageId 
 ); 
  
 } 
  
 }, 
  
 MoreExecutors 
 . 
 directExecutor 
 ()); 
  
 } 
  
 } 
  
 finally 
  
 { 
  
 // 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' 
 }); 
 // 
  
 const 
  
 orderingKey 
  
 = 
  
 'key1' 
 ; 
 // 
  
 Imports 
  
 the 
  
 Google 
  
 Cloud 
  
 client 
  
 library 
 const 
  
 { 
 PubSub 
 } 
  
 = 
  
 require 
 ( 
 '@google-cloud/pubsub' 
 ); 
 // 
  
 Creates 
  
 a 
  
 client 
 ; 
  
 cache 
  
 this 
  
 for 
  
 further 
  
 use 
 const 
  
 pubSubClient 
  
 = 
  
 new 
  
 PubSub 
 ({ 
  
 // 
  
 Sending 
  
 messages 
  
 to 
  
 the 
  
 same 
  
 region 
  
 ensures 
  
 they 
  
 are 
  
 received 
  
 in 
  
 order 
  
 // 
  
 even 
  
 when 
  
 multiple 
  
 publishers 
  
 are 
  
 used 
 . 
  
 apiEndpoint 
 : 
  
 'us-east1-pubsub.googleapis.com:443' 
 , 
 }); 
 async 
  
 function 
  
 publishOrderedMessage 
 ( 
 topicNameOrId 
 , 
  
 data 
 , 
  
 orderingKey 
 ) 
  
 { 
  
 // 
  
 Publishes 
  
 the 
  
 message 
  
 as 
  
 a 
  
 string 
 , 
  
 e 
 . 
 g 
 . 
  
 "Hello, world!" 
  
 or 
  
 JSON 
 . 
 stringify 
 ( 
 someObject 
 ) 
  
 const 
  
 dataBuffer 
  
 = 
  
 Buffer 
 . 
 from 
 ( 
 data 
 ); 
  
 // 
  
 Be 
  
 sure 
  
 to 
  
 set 
  
 an 
  
 ordering 
  
 key 
  
 that 
  
 matches 
  
 other 
  
 messages 
  
 // 
  
 you 
  
 want 
  
 to 
  
 receive 
  
 in 
  
 order 
 , 
  
 relative 
  
 to 
  
 each 
  
 other 
 . 
  
 const 
  
 message 
  
 = 
  
 { 
  
 data 
 : 
  
 dataBuffer 
 , 
  
 orderingKey 
 : 
  
 orderingKey 
 , 
  
 }; 
  
 // 
  
 Cache 
  
 topic 
  
 objects 
  
 ( 
 publishers 
 ) 
  
 and 
  
 reuse 
  
 them 
 . 
  
 // 
  
 // 
  
 Pub 
 / 
 Sub 
 's ordered delivery guarantee only applies when publishes for an ordering 
  
 // 
  
 key 
  
 are 
  
 in 
  
 the 
  
 same 
  
 region 
 . 
  
 For 
  
 list 
  
 of 
  
 locational 
  
 endpoints 
  
 for 
  
 Pub 
 / 
 Sub 
 , 
  
 see 
 : 
  
 // 
  
 https 
 : 
 // 
 cloud 
 . 
 google 
 . 
 com 
 / 
 pubsub 
 / 
 docs 
 / 
 reference 
 / 
 service_apis_overview 
 #list_of_locational_endpoints 
  
 const 
  
 publishOptions 
  
 = 
  
 { 
  
 messageOrdering 
 : 
  
 true 
 , 
  
 }; 
  
 const 
  
 topic 
  
 = 
  
 pubSubClient 
 . 
 topic 
 ( 
 topicNameOrId 
 , 
  
 publishOptions 
 ); 
  
 // 
  
 Publishes 
  
 the 
  
 message 
  
 const 
  
 messageId 
  
 = 
  
 await 
  
 topic 
 . 
 publishMessage 
 ( 
 message 
 ); 
  
 console 
 . 
 log 
 ( 
 ` 
 Message 
  
 $ 
 { 
 messageId 
 } 
  
 published 
 . 
 ` 
 ); 
  
 return 
  
 messageId 
 ; 
 }

    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' 
 }); 
 // 
 const 
 orderingKey 
 = 
 'key1' 
 ; 
 // 
 Imports 
 the 
 Google 
 Cloud 
 client 
 library 
 import 
  
 { 
 PublishOptions 
 , 
 PubSub 
 } 
 from 
  
 '@google-cloud/pubsub' 
 ; 
 // 
 Creates 
 a 
 client 
 ; 
 cache 
 this 
 for 
 further 
 use 
 const 
 pubSubClient 
 = 
 new 
 PubSub 
 ({ 
 // 
 Sending 
 messages 
 to 
 the 
 same 
 region 
 ensures 
 they 
 are 
 received 
 in 
 order 
 // 
 even 
 when 
 multiple 
 publishers 
 are 
 used 
 . 
 apiEndpoint 
 : 
 'us-east1-pubsub.googleapis.com:443' 
 , 
 }); 
 async 
 function 
 publishOrderedMessage 
 ( 
 topicNameOrId 
 : 
 string 
 , 
 data 
 : 
 string 
 , 
 orderingKey 
 : 
 string 
 , 
 ) 
 { 
 // 
 Publishes 
 the 
 message 
 as 
 a 
 string 
 , 
 e 
 . 
 g 
 . 
 "Hello, world!" 
 or 
 JSON 
 . 
 stringify 
 ( 
 someObject 
 ) 
 const 
 dataBuffer 
 = 
 Buffer 
 . 
 from 
 ( 
 data 
 ); 
 // 
 Be 
 sure 
 to 
 set 
 an 
 ordering 
 key 
 that 
 matches 
 other 
 messages 
 // 
 you 
 want 
 to 
 receive 
 in 
 order 
 , 
 relative 
 to 
 each 
 other 
 . 
 const 
 message 
 = 
 { 
 data 
 : 
 dataBuffer 
 , 
 orderingKey 
 : 
 orderingKey 
 , 
 }; 
 // 
 Cache 
 topic 
 objects 
 ( 
 publishers 
 ) 
 and 
 reuse 
 them 
 . 
 // 
 // 
 Pub 
 / 
 Sub 
 's ordered delivery guarantee only applies when publishes for an ordering 
 // 
 key 
 are 
 in 
 the 
 same 
 region 
 . 
 For 
 list 
 of 
 locational 
 endpoints 
 for 
 Pub 
 / 
 Sub 
 , 
 see 
 : 
 // 
 https 
 : 
 // 
 cloud 
 . 
 google 
 . 
 com 
 / 
 pubsub 
 / 
 docs 
 / 
 reference 
 / 
 service_apis_overview 
 #list_of_locational_endpoints 
 const 
 publishOptions 
 : 
 PublishOptions 
 = 
 { 
 messageOrdering 
 : 
 true 
 , 
 }; 
 const 
 topic 
 = 
 pubSubClient 
 . 
 topic 
 ( 
 topicNameOrId 
 , 
 publishOptions 
 ); 
 // 
 Publishes 
 the 
 message 
 const 
 messageId 
 = 
 await 
 topic 
 . 
 publishMessage 
 ( 
 message 
 ); 
 console 
 . 
 log 
 ( 
 ` 
 Message 
 $ 
 { 
 messageId 
 } 
 published 
 . 
 ` 
 ); 
 return 
 messageId 
 ; 
 }

    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 $topicName  The Pub/Sub topic name. 
 */ 
 function publish_with_ordering_keys($projectId, $topicName) 
 { 
 $pubsub = new PubSubClient([ 
 'projectId' => $projectId, 
 ]); 
 $topic = $pubsub->topic($topicName); 
 foreach (range(1, 5) as $i) { 
 $topic->publish((new MessageBuilder(['orderingKey' => 'foo'])) 
 ->setData('message' . $i)->build(), ['enableMessageOrdering' => true]); 
 } 
 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): Choose an existing topic. 
 # project_id = "your-project-id" 
 # topic_id = "your-topic-id" 
 publisher_options 
 = 
 pubsub_v1 
 . 
 types 
 . 
  PublisherOptions 
 
 ( 
 enable_message_ordering 
 = 
 True 
 ) 
 # Sending messages to the same region ensures they are received in order 
 # even when multiple publishers are used. 
 client_options 
 = 
 { 
 "api_endpoint" 
 : 
 "us-east1-pubsub.googleapis.com:443" 
 } 
 publisher 
 = 
 pubsub_v1 
 . 
  PublisherClient 
 
 ( 
 publisher_options 
 = 
 publisher_options 
 , 
 client_options 
 = 
 client_options 
 ) 
 # 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 
 message 
 in 
 [ 
 ( 
 "message1" 
 , 
 "key1" 
 ), 
 ( 
 "message2" 
 , 
 "key2" 
 ), 
 ( 
 "message3" 
 , 
 "key1" 
 ), 
 ( 
 "message4" 
 , 
 "key2" 
 ), 
 ]: 
 # Data must be a bytestring 
 data 
 = 
 message 
 [ 
 0 
 ] 
 . 
 encode 
 ( 
 "utf-8" 
 ) 
 ordering_key 
 = 
 message 
 [ 
 1 
 ] 
 # When you publish a message, the client returns a future. 
 future 
 = 
  publish 
 
er . 
  publish 
 
 ( 
 topic_path 
 , 
 data 
 = 
 data 
 , 
 ordering_key 
 = 
 ordering_key 
 ) 
 print 
 ( 
 future 
 . 
 result 
 ()) 
 print 
 ( 
 f 
 "Published messages with ordering keys 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 
 
 # Start sending messages in one request once the size of all queued messages 
 # reaches 1 MB or the number of queued messages reaches 20 
 publisher 
  
 = 
  
 pubsub 
 . 
  publisher 
 
  
 topic_id 
 , 
  
 async 
 : 
  
 { 
  
 max_bytes 
 : 
  
 1_000_000 
 , 
  
 max_messages 
 : 
  
 20 
 } 
 publisher 
 . 
 enable_message_ordering! 
 10 
 . 
 times 
  
 do 
  
 | 
 i 
 | 
  
 publisher 
 . 
  publish_async 
 
  
 "This is message # 
 #{ 
 i 
 } 
 ." 
 , 
  
 ordering_key 
 : 
  
 "ordering-key" 
 end 
 # Stop the async_publisher to send all queued messages immediately. 
 publisher 
 . 
  async_publisher 
 
 . 
 stop! 
 puts 
  
 "Messages published with ordering key."

    What's next

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