org.apache.drill.exec.store.kafka.MessageIterator.java Source code

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Here is the source code for org.apache.drill.exec.store.kafka.MessageIterator.java

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/*
 * 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.drill.exec.store.kafka;

import java.util.Iterator;
import java.util.List;
import java.util.concurrent.TimeUnit;

import org.apache.drill.common.exceptions.UserException;
import org.apache.drill.exec.ExecConstants;
import org.apache.drill.exec.store.kafka.KafkaSubScan.KafkaSubScanSpec;
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.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Stopwatch;
import com.google.common.collect.Lists;

import kafka.common.KafkaException;

public class MessageIterator implements Iterator<ConsumerRecord<byte[], byte[]>> {

    private static final Logger logger = LoggerFactory.getLogger(MessageIterator.class);
    private final KafkaConsumer<byte[], byte[]> kafkaConsumer;
    private Iterator<ConsumerRecord<byte[], byte[]>> recordIter;
    private final TopicPartition topicPartition;
    private long totalFetchTime = 0;
    private final long kafkaPollTimeOut;
    private final long endOffset;

    public MessageIterator(final KafkaConsumer<byte[], byte[]> kafkaConsumer, final KafkaSubScanSpec subScanSpec,
            final long kafkaPollTimeOut) {
        this.kafkaConsumer = kafkaConsumer;
        this.kafkaPollTimeOut = kafkaPollTimeOut;

        List<TopicPartition> partitions = Lists.newArrayListWithCapacity(1);
        topicPartition = new TopicPartition(subScanSpec.getTopicName(), subScanSpec.getPartitionId());
        partitions.add(topicPartition);
        this.kafkaConsumer.assign(partitions);
        logger.info("Start offset of {}:{} is - {}", subScanSpec.getTopicName(), subScanSpec.getPartitionId(),
                subScanSpec.getStartOffset());
        this.kafkaConsumer.seek(topicPartition, subScanSpec.getStartOffset());
        this.endOffset = subScanSpec.getEndOffset();
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("Does not support remove operation");
    }

    @Override
    public boolean hasNext() {
        if (recordIter != null && recordIter.hasNext()) {
            return true;
        }

        long nextPosition = kafkaConsumer.position(topicPartition);
        if (nextPosition >= endOffset) {
            return false;
        }

        ConsumerRecords<byte[], byte[]> consumerRecords = null;
        Stopwatch stopwatch = Stopwatch.createStarted();
        try {
            consumerRecords = kafkaConsumer.poll(kafkaPollTimeOut);
        } catch (KafkaException ke) {
            logger.error(ke.getMessage(), ke);
            throw UserException.dataReadError(ke).message(ke.getMessage()).build(logger);
        }
        stopwatch.stop();

        if (consumerRecords.isEmpty()) {
            String errorMsg = new StringBuilder().append("Failed to fetch messages within ")
                    .append(kafkaPollTimeOut)
                    .append(" milliseconds. Consider increasing the value of the property : ")
                    .append(ExecConstants.KAFKA_POLL_TIMEOUT).toString();
            throw UserException.dataReadError().message(errorMsg).build(logger);
        }

        long lastFetchTime = stopwatch.elapsed(TimeUnit.MILLISECONDS);
        logger.debug("Total number of messages fetched : {}", consumerRecords.count());
        logger.debug("Time taken to fetch : {} milliseconds", lastFetchTime);
        totalFetchTime += lastFetchTime;

        recordIter = consumerRecords.iterator();
        return recordIter.hasNext();
    }

    public long getTotalFetchTime() {
        return this.totalFetchTime;
    }

    @Override
    public ConsumerRecord<byte[], byte[]> next() {
        return recordIter.next();
    }
}