rmetzger commented on a change in pull request #6594: [FLINK-9311] [pubsub] Added PubSub source connector with support for checkpointing (ATLEAST_ONCE) URL: https://github.com/apache/flink/pull/6594#discussion_r257694803
########## File path: flink-connectors/flink-connector-pubsub/src/main/java/org/apache/flink/streaming/connectors/pubsub/SubscriberWrapper.java ########## @@ -0,0 +1,116 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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 org.apache.flink.streaming.connectors.pubsub; + +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.streaming.connectors.pubsub.common.PubSubSubscriberFactory; + +import com.google.api.core.ApiService; +import com.google.auth.Credentials; +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 org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.Serializable; +import java.util.Optional; +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.LinkedBlockingQueue; +import java.util.concurrent.TimeUnit; + +/** + * Wrapper class around a PubSub {@link Subscriber}. + * This class makes it easier to connect to a Non Google PubSub service such as a local PubSub emulator or docker container. + */ +class SubscriberWrapper implements Serializable, MessageReceiver { + private static final Logger LOG = LoggerFactory.getLogger(SubscriberWrapper.class); + + private final Credentials credentials; + private final String projectId; + private final String subscriptionId; + private final PubSubSubscriberFactory pubSubSubscriberFactory; + + private transient Subscriber subscriber; + private transient BlockingQueue<Tuple2<PubsubMessage, AckReplyConsumer>> messageQueue; + + SubscriberWrapper(Credentials credentials, ProjectSubscriptionName projectSubscriptionName, PubSubSubscriberFactory pubSubSubscriberFactory) { + this.credentials = credentials; + this.projectId = projectSubscriptionName.getProject(); + this.subscriptionId = projectSubscriptionName.getSubscription(); + this.pubSubSubscriberFactory = pubSubSubscriberFactory; + } + + void initialize() { + this.subscriber = pubSubSubscriberFactory.getSubscriber(credentials, ProjectSubscriptionName.of(projectId, subscriptionId), this); + this.messageQueue = new LinkedBlockingQueue<>(); + } + + void start() { + ApiService apiService = subscriber.startAsync(); + apiService.awaitRunning(); + } + + void stop() { + if (subscriber != null) { + subscriber.stopAsync().awaitTerminated(); + } + } + + Tuple2<PubsubMessage, AckReplyConsumer> take() throws InterruptedException { + return messageQueue.poll(1000L, TimeUnit.MILLISECONDS); + } + + private void nackAllMessagesInBuffer() throws InterruptedException { + LOG.debug("Going to nack {} messages.", amountOfMessagesInBuffer()); + while (!messageQueue.isEmpty()) { + Optional.ofNullable(messageQueue.poll(1000L, TimeUnit.MILLISECONDS)) + .map(tuple -> tuple.f1) + .ifPresent(AckReplyConsumer::nack); + } + LOG.debug("Finished nacking messages in buffer."); + } + + int amountOfMessagesInBuffer() { + return messageQueue.size(); + } + + boolean isRunning() { + return subscriber.isRunning(); + } + + void awaitTerminated() throws Exception { + nackAllMessagesInBuffer(); + subscriber.awaitTerminated(); + } + + @Override + public void receiveMessage(PubsubMessage message, AckReplyConsumer consumer) { + if (subscriber.isRunning()) { + messageQueue.offer(Tuple2.of(message, consumer)); Review comment: Thanks. I will start a discussion about backpressure in the main comments of the PR. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
