Yanikovic commented on a change in pull request #15140: URL: https://github.com/apache/flink/pull/15140#discussion_r594432519
########## File path: flink-connectors/flink-connector-rabbitmq2/src/main/java/org/apache/flink/connector/rabbitmq2/source/reader/RabbitMQSourceReaderBase.java ########## @@ -0,0 +1,262 @@ +/* + * 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.connector.rabbitmq2.source.reader; + +import org.apache.flink.api.common.serialization.DeserializationSchema; +import org.apache.flink.api.connector.source.ReaderOutput; +import org.apache.flink.api.connector.source.SourceEvent; +import org.apache.flink.api.connector.source.SourceReader; +import org.apache.flink.api.connector.source.SourceReaderContext; +import org.apache.flink.connector.base.source.reader.synchronization.FutureCompletingBlockingQueue; +import org.apache.flink.connector.rabbitmq2.source.common.RabbitMQMessageWrapper; +import org.apache.flink.connector.rabbitmq2.source.enumerator.RabbitMQSourceEnumerator; +import org.apache.flink.connector.rabbitmq2.source.split.RabbitMQSourceSplit; +import org.apache.flink.core.io.InputStatus; + +import com.rabbitmq.client.AMQP; +import com.rabbitmq.client.Channel; +import com.rabbitmq.client.Connection; +import com.rabbitmq.client.ConnectionFactory; +import com.rabbitmq.client.DeliverCallback; +import com.rabbitmq.client.Delivery; +import com.rabbitmq.client.Envelope; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; +import java.util.concurrent.CompletableFuture; + +/** + * The source reader for rabbitmq queues. This is the base class the different consistency modes. + * + * @param <T> The output type of the source. + */ +public abstract class RabbitMQSourceReaderBase<T> implements SourceReader<T, RabbitMQSourceSplit> { + protected static final Logger LOG = LoggerFactory.getLogger(RabbitMQSourceReaderBase.class); + + // The assigned split from the enumerator. + private RabbitMQSourceSplit split; + // Rabbitmq + private Connection rmqConnection; + private Channel rmqChannel; + + private final SourceReaderContext sourceReaderContext; + // The deserialization schema for the messages of rabbitmq. + private final DeserializationSchema<T> deliveryDeserializer; + // The collector keeps the messages received from rabbitmq. + private final RabbitMQCollector<T> collector; + + public RabbitMQSourceReaderBase( + SourceReaderContext sourceReaderContext, + DeserializationSchema<T> deliveryDeserializer) { + this.sourceReaderContext = sourceReaderContext; + this.deliveryDeserializer = deliveryDeserializer; + this.collector = new RabbitMQCollector<>(); + } + + @Override + public void start() { + LOG.info("Starting source reader and send split request"); + sourceReaderContext.sendSplitRequest(); + } + + // ------------- start rabbitmq methods -------------- + + private void setupRabbitMQ() { + try { + setupConnection(); + setupChannel(); + LOG.info( + "RabbitMQ Connection was successful: Waiting for messages from the queue. To exit press CTRL+C"); + } catch (Exception e) { + LOG.error(e.getMessage()); + } + } + + private ConnectionFactory setupConnectionFactory() throws Exception { + return split.getConnectionConfig().getConnectionFactory(); + } + + private void setupConnection() throws Exception { + rmqConnection = setupConnectionFactory().newConnection(); + } + + /** @return boolean whether messages should be automatically acknowledged to rabbitmq. */ + protected abstract boolean isAutoAck(); + + /** + * This function will be called when a new message from rabbitmq gets pushed to the source. The + * message will be deserialized and forwarded to our message collector where is buffered until + * it can be processed. + * + * @param consumerTag The consumer tag of the message. + * @param delivery The delivery from rabbitmq. + * @throws IOException if something fails during deserialization. + */ + protected void handleMessageReceivedCallback(String consumerTag, Delivery delivery) + throws IOException { + AMQP.BasicProperties properties = delivery.getProperties(); + byte[] body = delivery.getBody(); + Envelope envelope = delivery.getEnvelope(); + collector.setMessageIdentifiers(properties.getCorrelationId(), envelope.getDeliveryTag()); + deliveryDeserializer.deserialize(body, collector); + } + + protected void setupChannel() throws IOException { + rmqChannel = rmqConnection.createChannel(); + rmqChannel.queueDeclare(split.getQueueName(), true, false, false, null); + + // Set maximum of unacknowledged messages + if (getSplit().getConnectionConfig().getPrefetchCount().isPresent()) { + // global: false - the prefetch count is set per consumer, not per rabbitmq channel + rmqChannel.basicQos(getSplit().getConnectionConfig().getPrefetchCount().get(), false); + } + + final DeliverCallback deliverCallback = this::handleMessageReceivedCallback; + rmqChannel.basicConsume( + split.getQueueName(), isAutoAck(), deliverCallback, consumerTag -> {}); + } + + // ------------- end rabbitmq methods -------------- + + /** + * This method provides a hook that is called when a message gets polled by the output. + * + * @param message the message that was polled by the output. + */ + protected void handleMessagePolled(RabbitMQMessageWrapper<T> message) {} + + @Override + public InputStatus pollNext(ReaderOutput<T> output) { + RabbitMQMessageWrapper<T> message = collector.pollMessage(); + + if (message == null) { + return InputStatus.NOTHING_AVAILABLE; + } + + output.collect(message.getMessage()); + handleMessagePolled(message); + + return collector.hasUnpolledMessages() + ? InputStatus.MORE_AVAILABLE + : InputStatus.NOTHING_AVAILABLE; + } + + @Override + public List<RabbitMQSourceSplit> snapshotState(long checkpointId) { + return split != null ? Collections.singletonList(split.copy()) : new ArrayList<>(); + } + + @Override + public CompletableFuture<Void> isAvailable() { + return FutureCompletingBlockingQueue.AVAILABLE; Review comment: Yes it can happen. We propose to just check asynchronously in a loop if there are messages available. If they are, the Future completes. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to 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
