lang/java/trevni/avro/src/main/java/org/apache/trevni/avro/mapreduce/AvroTrevniKeyValueOutputFormat.java

/**
 * 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.trevni.avro.mapreduce;

import java.io.IOException;

import org.apache.avro.mapred.AvroKey;
import org.apache.avro.mapred.AvroValue;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

/** An {@link org.apache.hadoop.mapreduce.OutputFormat} that writes Avro data to
 * Trevni files.
 *
 * This implement was modeled off
 * {@link org.apache.avro.mapreduce.AvroKeyValueOutputFormat} to allow for easy
 * transition
 *
 *  * FileOutputFormat for writing Trevni container files of key/value pairs.
 *
 * <p>Since Trevni 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'.</p>
 *
 * <p>The keys and values given to this output format may be Avro objects wrapped in
 * <code>AvroKey</code> or <code>AvroValue</code> objects.  The basic Writable types are
 * also supported (e.g., IntWritable, Text); they will be converted to their corresponding
 * Avro types.</p>
 *
 * @param <K> The type of key. If an Avro type, it must be wrapped in an <code>AvroKey</code>.
 * @param <V> The type of value. If an Avro type, it must be wrapped in an <code>AvroValue</code>.
 *
 * <p>Writes a directory of files per task, each comprising a single filesystem
 * block.  To reduce the number of files, increase the default filesystem block
 * size for the job.  Each task also requires enough memory to buffer a
 * filesystem block.
 */
public class AvroTrevniKeyValueOutputFormat <K, V> extends FileOutputFormat<AvroKey<K>, AvroValue<V>> {

  /** {@inheritDoc} */
  @Override
  public RecordWriter<AvroKey<K>, AvroValue<V>> getRecordWriter(TaskAttemptContext context)
      throws IOException, InterruptedException {

    return new AvroTrevniKeyValueRecordWriter<K, V>(context );
  }
}