Package com.google.cloud.pubsub.v1

Class Subscriber

java.lang.Object
com.google.api.core.AbstractApiService
com.google.cloud.pubsub.v1.Subscriber
All Implemented Interfaces:
com.google.api.core.ApiService, SubscriberInterface
public class Subscriber extends com.google.api.core.AbstractApiService implements SubscriberInterface
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.

  • Method Details

    • newBuilder

      public static Subscriber.Builder newBuilder(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(ProjectSubscriptionName subscription, MessageReceiverWithAckResponse receiver)

    • 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

    • newBuilder

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

    • getDeliveryAttempt

      public static Integer getDeliveryAttempt(PubsubMessage message)
      Returns the delivery attempt count for a received PubsubMessage

    • getSubscriptionNameString

      public String getSubscriptionNameString()
      Subscription which the subscriber is subscribed to.

    • getFlowControlSettings

      public com.google.api.gax.batching.FlowControlSettings getFlowControlSettings()
      The flow control settings the Subscriber is configured with.

    • startAsync

      public com.google.api.core.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 com.google.api.core.ApiService
      Overrides:
      startAsync in class com.google.api.core.AbstractApiService

    • doStart

      protected void doStart()
      Specified by:
      doStart in class com.google.api.core.AbstractApiService

    • doStop

      protected void doStop()
      Specified by:
      doStop in class com.google.api.core.AbstractApiService