co.cask.cdap.hive.stream.StreamRecordReader.java Source code

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Here is the source code for co.cask.cdap.hive.stream.StreamRecordReader.java

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/*
 * Copyright  2014 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.hive.stream;

import co.cask.cdap.common.io.Locations;
import co.cask.cdap.data.file.ReadFilter;
import co.cask.cdap.data.stream.PositionStreamEvent;
import co.cask.cdap.data.stream.StreamDataFileReader;
import co.cask.cdap.data.stream.TimeRangeReadFilter;
import com.google.common.collect.Lists;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.io.ObjectWritable;
import org.apache.hadoop.mapred.InputSplit;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.RecordReader;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.List;
import java.util.concurrent.TimeUnit;

/**
 * A {@link org.apache.hadoop.mapred.RecordReader} for reading stream events in hive queries. This is different
 * enough from the mapreduce version that there is not a common class for the two.
 */
final class StreamRecordReader implements RecordReader<Void, ObjectWritable> {
    private static final Logger LOG = LoggerFactory.getLogger(StreamRecordReader.class);

    private final List<PositionStreamEvent> events;
    private final StreamDataFileReader reader;
    private final StreamInputSplit inputSplit;
    private final ReadFilter readFilter;

    StreamRecordReader(InputSplit split, JobConf conf) throws IOException {
        this.inputSplit = (StreamInputSplit) split;
        this.events = Lists.newArrayListWithCapacity(1);
        this.reader = createReader(FileSystem.get(conf), inputSplit);
        this.readFilter = new TimeRangeReadFilter(inputSplit.getStartTime(), inputSplit.getEndTime());
    }

    @Override
    public float getProgress() throws IOException {
        if (reader == null) {
            return 0.0f;
        }

        long processed = reader.getPosition() - inputSplit.getStart();
        return Math.min((float) processed / (float) inputSplit.getLength(), 1.0f);
    }

    @Override
    public boolean next(Void key, ObjectWritable value) throws IOException {
        events.clear();
        try {
            if (reader.read(events, 1, 0, TimeUnit.SECONDS, readFilter) <= 0) {
                return false;
            }
            PositionStreamEvent streamEvent = events.get(0);
            if (streamEvent.getStart() - inputSplit.getStart() >= inputSplit.getLength()) {
                return false;
            }
            value.set(streamEvent);
            return true;
        } catch (InterruptedException e) {
            LOG.error("interrupted while reading stream events.", e);
            return false;
        }
    }

    @Override
    public Void createKey() {
        return null;
    }

    @Override
    public ObjectWritable createValue() {
        // this method creates the value that is then passed into the next method, where it is set.
        return new ObjectWritable();
    }

    @Override
    public long getPos() throws IOException {
        // as far as I can tell, this doesn't do anything useful...
        return reader.getPosition();
    }

    @Override
    public void close() throws IOException {
        if (reader != null) {
            reader.close();
        }
    }

    /**
     * Creates a {@link co.cask.cdap.data.stream.StreamDataFileReader} based on the input split.
     *
     * @param fs The {@link org.apache.hadoop.fs.FileSystem} for the input.
     * @param inputSplit Split information.
     * @return A stream data file reader that is ready for reading events as specified by the input split.
     */
    private StreamDataFileReader createReader(FileSystem fs, StreamInputSplit inputSplit) throws IOException {
        StreamDataFileReader reader = StreamDataFileReader.createWithOffset(
                Locations.newInputSupplier(fs, inputSplit.getEventPath()), inputSplit.getIndexPath() == null ? null
                        : Locations.newInputSupplier(fs, inputSplit.getIndexPath()),
                inputSplit.getStart());
        try {
            reader.initialize();
            return reader;
        } catch (IOException e) {
            try {
                reader.close();
            } catch (IOException closeEx) {
                e.addSuppressed(closeEx);
            }
            throw e;
        }
    }
}