com.google.cloud.pubsub.v1

Class Subscriber

java.lang.Object

com.google.api.core.AbstractApiService

com.google.cloud.pubsub.v1.Subscriber

All Implemented Interfaces:

ApiService

public class Subscriber
extends AbstractApiService

A Cloud Pub/Sub subscriber that is associated with a specific subscription at creation.

A Subscriber allows you to provide an implementation of a receiver to which messages are going to be delivered as soon as they are received by the subscriber. The delivered messages then can be acked or nacked at will as they get processed by the receiver. Nacking a messages implies a later redelivery of such message.

The subscriber handles the ack management, by automatically extending the ack deadline while the message is being processed, to then issue the ack or nack of such message when the processing is done (see Subscriber.Builder.setMaxAckExtensionPeriod(Duration)). Note: message redelivery is still possible.

It also provides customizable options that control:

• Ack deadline extension: such as the amount of time ahead to trigger the extension of message acknowledgement expiration.
• Flow control: such as the maximum outstanding messages or maximum outstanding bytes to keep in memory before the receiver either ack or nack them.

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

Subscriber is implemented using Guava's Service and provides the same methods. See Guava documentation for more details.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Subscriber.Builder Builder of Subscribers.

Nested classes/interfaces inherited from interface com.google.api.core.ApiService

ApiService.Listener, ApiService.State

Method Summary

Modifier and Type	Method and Description
protected void	doStart()
protected void	doStop()
FlowControlSettings	getFlowControlSettings() The flow control settings the Subscriber is configured with.
String	getSubscriptionNameString() Subscription which the subscriber is subscribed to.
static Subscriber.Builder	newBuilder(com.google.pubsub.v1.ProjectSubscriptionName subscription, MessageReceiver receiver) Constructs a new Subscriber.Builder.
static Subscriber.Builder	newBuilder(String subscription, MessageReceiver receiver) Constructs a new Subscriber.Builder.
ApiService	startAsync() Initiates service startup and returns immediately.

Methods inherited from class com.google.api.core.AbstractApiService

addListener, awaitRunning, awaitRunning, awaitTerminated, awaitTerminated, failureCause, isRunning, notifyFailed, notifyStarted, notifyStopped, state, stopAsync

Methods inherited from class java.lang.Object

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

Method Detail

newBuilder

public static Subscriber.Builder newBuilder(com.google.pubsub.v1.ProjectSubscriptionName subscription,
                                            MessageReceiver receiver)

Constructs a new Subscriber.Builder.

Parameters:

subscription - Cloud Pub/Sub subscription to bind the subscriber to

receiver - an implementation of MessageReceiver used to process the received messages

newBuilder

public static Subscriber.Builder newBuilder(String subscription,
                                            MessageReceiver receiver)

Constructs a new Subscriber.Builder.

Parameters:

subscription - Cloud Pub/Sub subscription to bind the subscriber to

receiver - an implementation of MessageReceiver used to process the received messages

getSubscriptionNameString

public String getSubscriptionNameString()

Subscription which the subscriber is subscribed to.

getFlowControlSettings

public FlowControlSettings getFlowControlSettings()

The flow control settings the Subscriber is configured with.

startAsync

public ApiService startAsync()

Initiates service startup and returns immediately.

Example of receiving a specific number of messages.

 Subscriber subscriber = Subscriber.newBuilder(subscription, receiver).build();
 subscriber.addListener(new Subscriber.Listener() {
   public void failed(Subscriber.State from, Throwable failure) {
     // Handle error.
   }
 }, executor);
 subscriber.startAsync();

 // Wait for a stop signal.
 // In a server, this might be a signal to stop serving.
 // In this example, the signal is just a dummy Future.
 //
 // By default, Subscriber uses daemon threads (see
 // https://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html).
 // Consequently, once other threads have terminated, Subscriber will not stop the JVM from
 // exiting.
 // If the Subscriber should simply run forever, either use the setExecutorProvider method in
 // Subscriber.Builder
 // to use non-daemon threads or run
 //   for (;;) {
 //     Thread.sleep(Long.MAX_VALUE);
 //   }
 // at the end of main() to previent the main thread from exiting.
 done.get();
 subscriber.stopAsync().awaitTerminated();
 

Specified by:

startAsync in interface ApiService

Overrides:

startAsync in class AbstractApiService

doStart

protected void doStart()

Specified by:

doStart in class AbstractApiService

doStop

protected void doStop()

Specified by:

doStop in class AbstractApiService