/**
* 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.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.hadoop.io.AvroDatumConverter;
import org.apache.avro.hadoop.io.AvroDatumConverterFactory;
import org.apache.avro.hadoop.io.AvroKeyValue;
import org.apache.avro.mapred.AvroKey;
import org.apache.avro.mapred.AvroValue;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
/**
* Writes key/value pairs to an Trevni container file.
*
* <p>Each entry in the Trevni container file will be a generic record with two fields,
* named 'key' and 'value'. The input types may be basic Writable objects like Text or
* IntWritable, or they may be AvroWrapper subclasses (AvroKey or AvroValue). Writable
* objects will be converted to their corresponding Avro types when written to the generic
* record key/value pair.</p>
*
* @param <K> The type of key to write.
* @param <V> The type of value to write.
*/
public class AvroTrevniKeyValueRecordWriter <K, V> extends AvroTrevniRecordWriterBase<AvroKey<K>, AvroValue<V>, GenericRecord> {
/** The writer schema for the generic record entries of the Trevni container file. */
Schema mKeyValuePairSchema;
/** A reusable Avro generic record for writing key/value pairs to the file. */
AvroKeyValue<Object, Object> keyValueRecord;
/** A helper object that converts the input key to an Avro datum. */
AvroDatumConverter<K, ?> keyConverter;
/** A helper object that converts the input value to an Avro datum. */
AvroDatumConverter<V, ?> valueConverter;
/**
* Constructor.
* @param context The TaskAttempContext to supply the writer with information form the job configuration
*/
public AvroTrevniKeyValueRecordWriter(TaskAttemptContext context)
throws IOException {
super(context);
mKeyValuePairSchema = initSchema(context);
keyValueRecord = new AvroKeyValue<Object, Object>(new GenericData.Record(mKeyValuePairSchema));
}
/** {@inheritDoc} */
@Override
public void write(AvroKey<K> key, AvroValue<V> value) throws IOException,
InterruptedException {
keyValueRecord.setKey(key.datum());
keyValueRecord.setValue(value.datum());
writer.write(keyValueRecord.get());
if (writer.sizeEstimate() >= blockSize) // block full
flush();
}
/** {@inheritDoc} */
@SuppressWarnings("unchecked")
@Override
protected Schema initSchema(TaskAttemptContext context) {
AvroDatumConverterFactory converterFactory = new AvroDatumConverterFactory(
context.getConfiguration());
keyConverter = converterFactory.create((Class<K>) context
.getOutputKeyClass());
valueConverter = converterFactory.create((Class<V>) context
.getOutputValueClass());
// Create the generic record schema for the key/value pair.
return AvroKeyValue.getSchema(
keyConverter.getWriterSchema(), valueConverter.getWriterSchema());
}
}