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SubscribeWithConcurrencyControlExample.java
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SubscribeWithConcurrencyControlExample.java
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/*
* Copyright 2016 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package pubsub;
// [START pubsub_subscriber_concurrency_control]
import com.google.api.gax.core.ExecutorProvider;
import com.google.api.gax.core.InstantiatingExecutorProvider;
import com.google.cloud.pubsub.v1.AckReplyConsumer;
import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsub.v1.Subscriber;
import com.google.pubsub.v1.ProjectSubscriptionName;
import com.google.pubsub.v1.PubsubMessage;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class SubscribeWithConcurrencyControlExample {
public static void main(String... args) throws Exception {
// TODO(developer): Replace these variables before running the sample.
String projectId = "your-project-id";
String subscriptionId = "your-subscription-id";
subscribeWithConcurrencyControlExample(projectId, subscriptionId);
}
public static void subscribeWithConcurrencyControlExample(
String projectId, String subscriptionId) {
ProjectSubscriptionName subscriptionName =
ProjectSubscriptionName.of(projectId, subscriptionId);
// Instantiate an asynchronous message receiver.
MessageReceiver receiver =
(PubsubMessage message, AckReplyConsumer consumer) -> {
// Handle incoming message, then ack the received message.
System.out.println("Id: " + message.getMessageId());
System.out.println("Data: " + message.getData().toStringUtf8());
consumer.ack();
};
Subscriber subscriber = null;
try {
// Provides an executor service for processing messages. The default `executorProvider` used
// by the subscriber has a default thread count of 5.
ExecutorProvider executorProvider =
InstantiatingExecutorProvider.newBuilder().setExecutorThreadCount(4).build();
// `setParallelPullCount` determines how many StreamingPull streams the subscriber will open
// to receive message. It defaults to 1. `setExecutorProvider` configures an executor for the
// subscriber to process messages. Here, the subscriber is configured to open 2 streams for
// receiving messages, each stream creates a new executor with 4 threads to help process the
// message callbacks. In total 2x4=8 threads are used for message processing.
subscriber =
Subscriber.newBuilder(subscriptionName, receiver)
.setParallelPullCount(2)
.setExecutorProvider(executorProvider)
.build();
// Start the subscriber.
subscriber.startAsync().awaitRunning();
System.out.printf("Listening for messages on %s:\n", subscriptionName.toString());
// Allow the subscriber to run for 30s unless an unrecoverable error occurs.
subscriber.awaitTerminated(30, TimeUnit.SECONDS);
} catch (TimeoutException timeoutException) {
// Shut down the subscriber after 30s. Stop receiving messages.
subscriber.stopAsync();
}
}
}
// [END pubsub_subscriber_concurrency_control]