com.google.cloud.pubsub.v1

Class Publisher

java.lang.Object

com.google.cloud.pubsub.v1.Publisher

All Implemented Interfaces:

PublisherInterface

public class Publisher
extends Object
implements PublisherInterface

A Cloud Pub/Sub publisher, that is associated with a specific topic at creation.

A Publisher provides built-in capabilities to automatically handle batching of messages, controlling memory utilization, and retrying API calls on transient errors.

With customizable options that control:

• Message batching: such as number of messages or max batch byte size.
• Retries: such as the maximum duration of retries for a failing batch of messages.

Publisher will use the credentials set on the channel, which uses application default credentials through GoogleCredentials.getApplicationDefault() by default.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Publisher.Builder A builder of Publishers.

Method Summary

Modifier and Type	Method and Description
boolean	awaitTermination(long duration, TimeUnit unit) Wait for all work has completed execution after a shutdown() request, or the timeout occurs, or the current thread is interrupted.
static long	getApiMaxRequestBytes() The maximum size of one request.
static long	getApiMaxRequestElementCount() The maximum number of messages in one request.
com.google.api.gax.batching.BatchingSettings	getBatchingSettings() The batching settings configured on this Publisher.
TopicName	getTopicName() Topic which the publisher publishes to.
String	getTopicNameString() Topic which the publisher publishes to.
static Publisher.Builder	newBuilder(String topicName) Constructs a new Publisher.Builder using the given topic.
static Publisher.Builder	newBuilder(TopicName topicName) Constructs a new Publisher.Builder using the given topic.
com.google.api.core.ApiFuture<String>	publish(PubsubMessage message) Schedules the publishing of a message.
void	publishAllOutstanding() Publish any outstanding batches if non-empty.
void	resumePublish(String key) There may be non-recoverable problems with a request for an ordering key.
void	shutdown() Schedules immediate publishing of any outstanding messages and waits until all are processed.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getApiMaxRequestElementCount

public static long getApiMaxRequestElementCount()

The maximum number of messages in one request. Defined by the API.

getApiMaxRequestBytes

public static long getApiMaxRequestBytes()

The maximum size of one request. Defined by the API.

getTopicName

public TopicName getTopicName()

Topic which the publisher publishes to.

getTopicNameString

public String getTopicNameString()

Topic which the publisher publishes to.

publish

public com.google.api.core.ApiFuture<String> publish(PubsubMessage message)

Schedules the publishing of a message. The publishing of the message may occur immediately or be delayed based on the publisher batching options.

This method blocks in the downcall if using LimitExceededBehavior.Block in the flow control settings.

Example of publishing a message.

 String message = "my_message";
 ByteString data = ByteString.copyFromUtf8(message);
 PubsubMessage pubsubMessage = PubsubMessage.newBuilder().setData(data).build();
 ApiFuture<String> messageIdFuture = publisher.publish(pubsubMessage);
 ApiFutures.addCallback(messageIdFuture, new ApiFutureCallback<String>() {
   public void onSuccess(String messageId) {
     System.out.println("published with message id: " + messageId);
   }

   public void onFailure(Throwable t) {
     System.out.println("failed to publish: " + t);
   }
 }, MoreExecutors.directExecutor());
 

Specified by:

publish in interface PublisherInterface

Parameters:

message - the message to publish.

Returns:

the message ID wrapped in a future.

resumePublish

public void resumePublish(String key)

There may be non-recoverable problems with a request for an ordering key. In that case, all subsequent requests will fail until this method is called. If the key is not currently paused, calling this method will be a no-op.

Parameters:

key - The key for which to resume publishing.

publishAllOutstanding

public void publishAllOutstanding()

Publish any outstanding batches if non-empty. This method sends buffered messages, but does not wait for the send operations to complete. To wait for messages to send, call get on the futures returned from publish.

getBatchingSettings

public com.google.api.gax.batching.BatchingSettings getBatchingSettings()

The batching settings configured on this Publisher.

shutdown

public void shutdown()

Schedules immediate publishing of any outstanding messages and waits until all are processed.

Sends remaining outstanding messages and prevents future calls to publish. This method should be invoked prior to deleting the Publisher object in order to ensure that no pending messages are lost.

awaitTermination

public boolean awaitTermination(long duration,
                                TimeUnit unit)
                         throws InterruptedException

Wait for all work has completed execution after a shutdown() request, or the timeout occurs, or the current thread is interrupted.

Call this method to make sure all resources are freed properly.

Throws:

InterruptedException

newBuilder

public static Publisher.Builder newBuilder(TopicName topicName)

Constructs a new Publisher.Builder using the given topic.

Example of creating a Publisher.

 String projectName = "my_project";
 String topicName = "my_topic";
 ProjectTopicName topic = ProjectTopicName.create(projectName, topicName);
 Publisher publisher = Publisher.newBuilder(topic).build();
 try {
   // ...
 } finally {
   // When finished with the publisher, make sure to shutdown to free up resources.
   publisher.shutdown();
   publisher.awaitTermination(1, TimeUnit.MINUTES);
 }
 

newBuilder

public static Publisher.Builder newBuilder(String topicName)

Constructs a new Publisher.Builder using the given topic.

Example of creating a Publisher.

 String topic = "projects/my_project/topics/my_topic";
 Publisher publisher = Publisher.newBuilder(topic).build();
 try {
   // ...
 } finally {
   // When finished with the publisher, make sure to shutdown to free up resources.
   publisher.shutdown();
   publisher.awaitTermination(1, TimeUnit.MINUTES);
 }