Xeli 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_r271059377
########## File path: flink-connectors/flink-connector-gcp-pubsub/src/main/java/org/apache/flink/streaming/connectors/gcp/pubsub/PubSubSource.java ########## @@ -0,0 +1,296 @@ +/* + * 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.gcp.pubsub; + +import org.apache.flink.api.common.functions.RuntimeContext; +import org.apache.flink.api.common.functions.StoppableFunction; +import org.apache.flink.api.common.serialization.DeserializationSchema; +import org.apache.flink.api.common.typeinfo.TypeInformation; +import org.apache.flink.api.java.typeutils.ResultTypeQueryable; +import org.apache.flink.configuration.Configuration; +import org.apache.flink.streaming.api.functions.source.MultipleIdsMessageAcknowledgingSourceBase; +import org.apache.flink.streaming.api.functions.source.ParallelSourceFunction; +import org.apache.flink.streaming.api.operators.StreamingRuntimeContext; +import org.apache.flink.streaming.connectors.gcp.pubsub.common.PubSubSubscriberFactory; +import org.apache.flink.util.Preconditions; + +import com.google.api.core.ApiFuture; +import com.google.auth.Credentials; +import com.google.cloud.pubsub.v1.Subscriber; +import com.google.cloud.pubsub.v1.stub.SubscriberStub; +import com.google.pubsub.v1.AcknowledgeRequest; +import com.google.pubsub.v1.ProjectSubscriptionName; +import com.google.pubsub.v1.PubsubMessage; +import com.google.pubsub.v1.PullRequest; +import com.google.pubsub.v1.PullResponse; +import com.google.pubsub.v1.ReceivedMessage; +import io.grpc.netty.shaded.io.netty.channel.EventLoopGroup; +import io.grpc.netty.shaded.io.netty.channel.nio.NioEventLoopGroup; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.IOException; +import java.util.List; +import java.util.concurrent.CancellationException; +import java.util.concurrent.TimeUnit; + +import static com.google.cloud.pubsub.v1.SubscriptionAdminSettings.defaultCredentialsProviderBuilder; + +/** + * PubSub Source, this Source will consume PubSub messages from a subscription and Acknowledge them on the next checkpoint. + * This ensures every message will get acknowledged at least once. + */ +public class PubSubSource<OUT> extends MultipleIdsMessageAcknowledgingSourceBase<OUT, String, String> + implements ResultTypeQueryable<OUT>, ParallelSourceFunction<OUT>, StoppableFunction { + private static final Logger LOG = LoggerFactory.getLogger(PubSubSource.class); + protected final DeserializationSchema<OUT> deserializationSchema; + protected final PubSubSubscriberFactory pubSubSubscriberFactory; + protected final Credentials credentials; + protected final String projectSubscriptionName; + protected final int maxMessagesPerPull; + + protected transient boolean deduplicateMessages; + protected transient SubscriberStub subscriber; + protected transient PullRequest pullRequest; + protected transient EventLoopGroup eventLoopGroup; + + protected transient volatile boolean isRunning; + protected transient volatile ApiFuture<PullResponse> messagesFuture; + + PubSubSource(DeserializationSchema<OUT> deserializationSchema, PubSubSubscriberFactory pubSubSubscriberFactory, Credentials credentials, String projectSubscriptionName, int maxMessagesPerPull) { + super(String.class); + this.deserializationSchema = deserializationSchema; + this.pubSubSubscriberFactory = pubSubSubscriberFactory; + this.credentials = credentials; + this.projectSubscriptionName = projectSubscriptionName; + this.maxMessagesPerPull = maxMessagesPerPull; + } + + @Override + public void open(Configuration configuration) throws Exception { + super.open(configuration); + if (hasNoCheckpointingEnabled(getRuntimeContext())) { + throw new IllegalArgumentException("The PubSubSource REQUIRES Checkpointing to be enabled and " + + "the checkpointing frequency must be MUCH lower than the PubSub timeout for it to retry a message."); + } + + getRuntimeContext().getMetricGroup().gauge("PubSubMessagesProcessedNotAcked", this::getOutstandingMessagesToAck); + + this.eventLoopGroup = new NioEventLoopGroup(); + this.subscriber = pubSubSubscriberFactory.getSubscriber(eventLoopGroup, credentials); + this.deduplicateMessages = getRuntimeContext().getNumberOfParallelSubtasks() == 1; + this.isRunning = true; + this.pullRequest = PullRequest.newBuilder() + .setMaxMessages(100) + .setReturnImmediately(false) + .setSubscription(projectSubscriptionName) + .build(); + } + + private boolean hasNoCheckpointingEnabled(RuntimeContext runtimeContext) { + return !(runtimeContext instanceof StreamingRuntimeContext && ((StreamingRuntimeContext) runtimeContext).isCheckpointingEnabled()); + } + + @Override + protected void acknowledgeSessionIDs(List<String> acknowledgementIds) { + if (acknowledgementIds.isEmpty() || !isRunning) { + return; + } + + AcknowledgeRequest acknowledgeRequest = + AcknowledgeRequest.newBuilder() + .setSubscription(projectSubscriptionName) + .addAllAckIds(acknowledgementIds) + .build(); + subscriber.acknowledgeCallable().call(acknowledgeRequest); + } + + @Override + public void run(SourceContext<OUT> sourceContext) throws Exception { + while (isRunning) { + messagesFuture = subscriber.pullCallable().futureCall(pullRequest); + try { + processMessage(sourceContext, messagesFuture.get().getReceivedMessagesList()); + } catch (InterruptedException | CancellationException e) { + awaitSubscriberTermination(); + return; + } + } + + awaitSubscriberTermination(); + } + + void processMessage(SourceContext<OUT> sourceContext, List<ReceivedMessage> messages) throws IOException { + synchronized (sourceContext.getCheckpointLock()) { + for (ReceivedMessage message : messages) { + sessionIds.add(message.getAckId()); + + PubsubMessage pubsubMessage = message.getMessage(); + if (deduplicateMessages && !addId(pubsubMessage.getMessageId())) { + // message is duplicate so just ignore it + return; + } + + OUT deserializedMessage = deserializeMessage(pubsubMessage); + if (deserializationSchema.isEndOfStream(deserializedMessage)) { + stop(); + return; + } + + sourceContext.collect(deserializedMessage); + } + + } + } + + private Integer getOutstandingMessagesToAck() { + return this.sessionIdsPerSnapshot + .stream() + .mapToInt(tuple -> tuple.f1.size()) + .sum() + this.sessionIds.size(); + } + + @Override + public void cancel() { + stop(); + } + + @Override + public void stop() { Review comment: I've removed the StoppableFunction interface as I noticed it might get deprecated soonish in FLINK-11889 and have changed the `cancel()` to just set a boolean to false as per your suggestion. 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