org.apache.crunch.io.avro.trevni.TrevniRecordWriter.java Source code

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Here is the source code for org.apache.crunch.io.avro.trevni.TrevniRecordWriter.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.crunch.io.avro.trevni;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Iterator;
import java.util.Map.Entry;

import org.apache.avro.Schema;
import org.apache.avro.mapred.AvroKey;
import org.apache.avro.mapreduce.AvroJob;
import org.apache.avro.reflect.ReflectData;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.trevni.ColumnFileMetaData;
import org.apache.trevni.MetaData;
import org.apache.trevni.avro.AvroColumnWriter;

/**
 *
 */
public class TrevniRecordWriter<T> extends RecordWriter<AvroKey<T>, NullWritable> {

    /** trevni file extension */
    public final static String EXT = ".trv";

    /** prefix of job configs that we care about */
    public static final String META_PREFIX = "trevni.meta.";

    /** Counter that increments as new trevni files are create because the current file 
     * has exceeded the block size 
     * */
    protected int part = 0;

    /** Trevni file writer */
    protected AvroColumnWriter<T> writer;

    /** This will be a unique directory linked to the task */
    final Path dirPath;

    /** HDFS object */
    final FileSystem fs;

    /** Current configured blocksize */
    final long blockSize;

    /** Provided avro schema from the context */
    protected Schema schema;

    /** meta data to be stored in the output file.  */
    protected ColumnFileMetaData meta;

    public TrevniRecordWriter(TaskAttemptContext context) throws IOException {
        schema = initSchema(context);
        meta = filterMetadata(context.getConfiguration());
        writer = new AvroColumnWriter<T>(schema, meta, ReflectData.get());

        Path outputPath = FileOutputFormat.getOutputPath(context);

        String dir = FileOutputFormat.getUniqueFile(context, "part", "");
        dirPath = new Path(outputPath.toString() + "/" + dir);
        fs = dirPath.getFileSystem(context.getConfiguration());
        fs.mkdirs(dirPath);

        blockSize = fs.getDefaultBlockSize();
    }

    /** {@inheritDoc} */
    @Override
    public void write(AvroKey<T> key, NullWritable value) throws IOException, InterruptedException {
        writer.write(key.datum());
        if (writer.sizeEstimate() >= blockSize) // block full
            flush();
    }

    /** {@inheritDoc} */
    protected Schema initSchema(TaskAttemptContext context) {
        boolean isMapOnly = context.getNumReduceTasks() == 0;
        return isMapOnly ? AvroJob.getMapOutputKeySchema(context.getConfiguration())
                : AvroJob.getOutputKeySchema(context.getConfiguration());
    }

    /**
     * A Trevni flush will close the current file and prep a new writer
     * @throws IOException
     */
    public void flush() throws IOException {
        OutputStream out = fs.create(new Path(dirPath, "part-" + (part++) + EXT));
        try {
            writer.writeTo(out);
        } finally {
            out.close();
        }
        writer = new AvroColumnWriter<T>(schema, meta, ReflectData.get());
    }

    /** {@inheritDoc} */
    @Override
    public void close(TaskAttemptContext arg0) throws IOException, InterruptedException {
        flush();
    }

    static ColumnFileMetaData filterMetadata(final Configuration configuration) {
        final ColumnFileMetaData meta = new ColumnFileMetaData();
        Iterator<Entry<String, String>> keyIterator = configuration.iterator();

        while (keyIterator.hasNext()) {
            Entry<String, String> confEntry = keyIterator.next();
            if (confEntry.getKey().startsWith(META_PREFIX))
                meta.put(confEntry.getKey().substring(META_PREFIX.length()),
                        confEntry.getValue().getBytes(MetaData.UTF8));
        }

        return meta;
    }
}