notification/src/main/java/org/apache/atlas/kafka/AtlasKafkaConsumer.java

/**
 * 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.atlas.kafka;

import org.apache.atlas.notification.AbstractNotificationConsumer;
import org.apache.atlas.notification.MessageDeserializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.clients.consumer.OffsetAndMetadata;

/**
 * Kafka specific notification consumer.
 *
 * @param <T> the notification type returned by this consumer
 */
public class AtlasKafkaConsumer<T> extends AbstractNotificationConsumer<T> {
    private static final Logger LOG = LoggerFactory.getLogger(AtlasKafkaConsumer.class);

    private final KafkaConsumer kafkaConsumer;
    private final boolean       autoCommitEnabled;

    public AtlasKafkaConsumer(MessageDeserializer<T> deserializer, KafkaConsumer kafkaConsumer, boolean autoCommitEnabled) {
        super(deserializer);

        this.kafkaConsumer     = kafkaConsumer;
        this.autoCommitEnabled = autoCommitEnabled;
    }

    public List<AtlasKafkaMessage<T>> receive(long timeoutMilliSeconds) {
        List<AtlasKafkaMessage<T>> messages = new ArrayList();

        ConsumerRecords<?, ?> records = kafkaConsumer.poll(timeoutMilliSeconds);

        if (records != null) {
            for (ConsumerRecord<?, ?> record : records) {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Received Message topic ={}, partition ={}, offset = {}, key = {}, value = {}",
                            record.topic(), record.partition(), record.offset(), record.key(), record.value());
                }

                T message = deserializer.deserialize(record.value().toString());

                messages.add(new AtlasKafkaMessage(message, record.offset(), record.partition()));
            }
        }

        return messages;
    }


    @Override
    public void commit(TopicPartition partition, long offset) {
        if (!autoCommitEnabled) {
            if (LOG.isDebugEnabled()) {
                LOG.info(" commiting the offset ==>> " + offset);
            }
            kafkaConsumer.commitSync(Collections.singletonMap(partition, new OffsetAndMetadata(offset)));
        }
    }

    @Override
    public void close() {
        if (kafkaConsumer != null) {
            kafkaConsumer.close();
        }
    }
}