it.crs4.pydoop.mapreduce.pipes.PydoopAvroRecordReaderBase.java Source code

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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 it.crs4.pydoop.mapreduce.pipes;

import java.io.IOException;

import org.apache.avro.Schema;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.file.DataFileReader;
import org.apache.avro.file.SeekableInput;
import org.apache.avro.mapred.FsInput;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public abstract class PydoopAvroRecordReaderBase<K, V> extends RecordReader<K, V> {

    private static final Logger LOG = LoggerFactory.getLogger(PydoopAvroRecordReaderBase.class);

    private final Schema mReaderSchema;
    private GenericRecord mCurrentRecord;
    private DataFileReader<GenericRecord> mAvroFileReader;
    private long mStartPosition;
    private long mEndPosition;

    protected PydoopAvroRecordReaderBase(Schema readerSchema) {
        mReaderSchema = readerSchema;
        mCurrentRecord = null;
    }

    @Override
    public void initialize(InputSplit inputSplit, TaskAttemptContext context)
            throws IOException, InterruptedException {
        if (!(inputSplit instanceof FileSplit)) {
            throw new IllegalArgumentException("Only compatible with FileSplits.");
        }
        FileSplit fileSplit = (FileSplit) inputSplit;
        SeekableInput seekableFileInput = createSeekableInput(context.getConfiguration(), fileSplit.getPath());
        mAvroFileReader = new DataFileReader<GenericRecord>(seekableFileInput,
                new GenericDatumReader<GenericRecord>(mReaderSchema));
        // We will read the first block that begins after the input split
        // start; we will read up to but not including the first block
        // that begins after the input split end.
        mAvroFileReader.sync(fileSplit.getStart());
        mStartPosition = mAvroFileReader.previousSync();
        mEndPosition = fileSplit.getStart() + fileSplit.getLength();
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        assert null != mAvroFileReader;
        if (mAvroFileReader.hasNext() && !mAvroFileReader.pastSync(mEndPosition)) {
            mCurrentRecord = mAvroFileReader.next(mCurrentRecord);
            return true;
        }
        return false;
    }

    @Override
    public float getProgress() throws IOException, InterruptedException {
        assert null != mAvroFileReader;
        if (mEndPosition == mStartPosition) {
            return 0.0f;
        }
        long bytesRead = mAvroFileReader.previousSync() - mStartPosition;
        long bytesTotal = mEndPosition - mStartPosition;
        LOG.debug("Progress: bytesRead=" + bytesRead + ", bytesTotal=" + bytesTotal);
        return Math.min(1.0f, (float) bytesRead / (float) bytesTotal);
    }

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

    protected GenericRecord getCurrentRecord() {
        return mCurrentRecord;
    }

    protected SeekableInput createSeekableInput(Configuration conf, Path path) throws IOException {
        return new FsInput(path, conf);
    }
}