datafu.hourglass.avro.AvroKeyValueWithMetadataOutputFormat Maven / Gradle / Ivy

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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 datafu.hourglass.avro;

import java.io.IOException;

import org.apache.avro.hadoop.io.AvroDatumConverter;
import org.apache.avro.hadoop.io.AvroDatumConverterFactory;
import org.apache.avro.mapreduce.AvroOutputFormatBase;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;

/**
 * FileOutputFormat for writing Avro container files of key/value pairs.
 *
 * Since Avro container files can only contain records (not key/value pairs), this
 * output format puts the key and value into an Avro generic record with two fields, named
 * 'key' and 'value'.
 *
 * The keys and values given to this output format may be Avro objects wrapped in
 * AvroKey or AvroValue objects.  The basic Writable types are
 * also supported (e.g., IntWritable, Text); they will be converted to their corresponding
 * Avro types.
 *
 * @param  The type of key. If an Avro type, it must be wrapped in an AvroKey.
 * @param  The type of value. If an Avro type, it must be wrapped in an AvroValue.
 */
public class AvroKeyValueWithMetadataOutputFormat extends AvroOutputFormatBase {
  /** {@inheritDoc} */
  @Override
  @SuppressWarnings("unchecked")
  public RecordWriter getRecordWriter(TaskAttemptContext context) throws IOException {
    AvroDatumConverterFactory converterFactory = new AvroDatumConverterFactory(
        context.getConfiguration());

    AvroDatumConverter keyConverter = converterFactory.create(
        (Class) context.getOutputKeyClass());
    AvroDatumConverter valueConverter = converterFactory.create(
        (Class) context.getOutputValueClass());
    
    return new AvroKeyValueWithMetadataRecordWriter(keyConverter, valueConverter,
        getCompressionCodec(context), getAvroFileOutputStream(context), context.getConfiguration());
  }
}