XuMingmin commented on a change in pull request #1127: [CALCITE-2913] Adapter for Apache Kafka URL: https://github.com/apache/calcite/pull/1127#discussion_r284359183
########## File path: kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaMessageEnumerator.java ########## @@ -0,0 +1,93 @@ +/* + * 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.calcite.adapter.kafka; + +import org.apache.calcite.linq4j.Enumerator; + +import org.apache.kafka.clients.consumer.Consumer; +import org.apache.kafka.clients.consumer.ConsumerConfig; +import org.apache.kafka.clients.consumer.ConsumerRecord; +import org.apache.kafka.clients.consumer.ConsumerRecords; + +import java.time.Duration; +import java.util.LinkedList; +import java.util.concurrent.atomic.AtomicBoolean; + +/** + * Enumerator to read data from {@link Consumer}, + * and converted into SQL rows with {@link KafkaRowConverter}. + * @param <K>: type for Kafka message key, + * refer to {@link ConsumerConfig#KEY_DESERIALIZER_CLASS_CONFIG}; + * @param <V>: type for Kafka message value, + * refer to {@link ConsumerConfig#VALUE_DESERIALIZER_CLASS_CONFIG}; + */ +public class KafkaMessageEnumerator<K, V> implements Enumerator<Object[]> { + final Consumer consumer; + final KafkaRowConverter<K, V> rowConverter; + private final AtomicBoolean cancelFlag; + + //runtime + private final LinkedList<ConsumerRecord<K, V>> bufferedRecords = new LinkedList<>(); + private ConsumerRecord<K, V> curRecord; + + KafkaMessageEnumerator(final Consumer consumer, + final KafkaRowConverter<K, V> rowConverter, + final AtomicBoolean cancelFlag) { + this.consumer = consumer; + this.rowConverter = rowConverter; + this.cancelFlag = cancelFlag; + } + + /** + * It returns an Array of Object, with each element represents a field of row. + */ + @Override public Object[] current() { + return rowConverter.toRow(curRecord); + } + + @Override public boolean moveNext() { + if (cancelFlag.get()) { + return false; + } + + while (bufferedRecords.isEmpty()) { + pullRecords(); + } + + curRecord = bufferedRecords.removeFirst(); + return true; + } + + private void pullRecords() { + ConsumerRecords<K, V> records = consumer.poll(Duration.ofMillis(100)); + for (ConsumerRecord record : records) { + bufferedRecords.add(record); + } + + consumer.commitSync(); Review comment: I would remove this line directly. If users need auto-commit, they can set in `consumer.params` ---------------------------------------------------------------- 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: [email protected] With regards, Apache Git Services
