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_r257314300
########## File path: flink-connectors/flink-connector-pubsub/src/main/java/org/apache/flink/streaming/connectors/pubsub/PubSubSource.java ########## @@ -0,0 +1,294 @@ +/* + * 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.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.tuple.Tuple2; +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.pubsub.common.PubSubSubscriberFactory; + +import com.google.auth.Credentials; +import com.google.cloud.pubsub.v1.AckReplyConsumer; +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.IOException; +import java.util.List; +import java.util.Optional; + +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, AckReplyConsumer> + implements ResultTypeQueryable<OUT>, ParallelSourceFunction<OUT>, StoppableFunction { + private static final Logger LOG = LoggerFactory.getLogger(PubSubSource.class); + protected DeserializationSchema<OUT> deserializationSchema; + protected SubscriberWrapper subscriberWrapper; + + protected boolean running = true; + protected transient volatile SourceContext<OUT> sourceContext = null; + + protected PubSubSource() { + super(String.class); + } + + protected void setDeserializationSchema(DeserializationSchema<OUT> deserializationSchema) { + this.deserializationSchema = deserializationSchema; + } + + protected void setSubscriberWrapper(SubscriberWrapper subscriberWrapper) { + this.subscriberWrapper = subscriberWrapper; + } + + @Override + public void open(Configuration configuration) throws Exception { + super.open(configuration); + subscriberWrapper.initialize(); + 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); + getRuntimeContext().getMetricGroup().gauge("PubSubMessagesReceivedNotProcessed", subscriberWrapper::amountOfMessagesInBuffer); + } + + private boolean hasNoCheckpointingEnabled(RuntimeContext runtimeContext) { + return !(runtimeContext instanceof StreamingRuntimeContext && ((StreamingRuntimeContext) runtimeContext).isCheckpointingEnabled()); + } + + @Override + protected void acknowledgeSessionIDs(List<AckReplyConsumer> ackReplyConsumers) { + ackReplyConsumers.forEach(AckReplyConsumer::ack); + } + + @Override + public void run(SourceContext<OUT> sourceContext) throws Exception { + this.sourceContext = sourceContext; + subscriberWrapper.start(); + + while (subscriberWrapper.isRunning()) { + try { + Optional.ofNullable(subscriberWrapper.take()) + .ifPresent(this::processMessage); + } catch (InterruptedException e) { + LOG.debug("Interrupted - stop or cancel called?"); + } + } + + nackOutstandingMessages(); Review comment: Why do we notify the system to re-send messages? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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