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

Go to download
/**
 * 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 java.io.OutputStream;

import org.apache.avro.Schema;
import org.apache.avro.file.CodecFactory;
import org.apache.avro.mapred.AvroKey;
import org.apache.avro.mapreduce.AvroJob;
import org.apache.avro.mapreduce.AvroOutputFormatBase;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;

/**
 * FileOutputFormat for writing Avro container files.
 *
 * Since Avro container files only contain records (not key/value pairs), this output
 * format ignores the value.
 *
 * @param  The (java) type of the Avro data to write.
 */
public class AvroKeyWithMetadataOutputFormat extends AvroOutputFormatBase, NullWritable> {
  /** A factory for creating record writers. */
  @SuppressWarnings("rawtypes")
  private final RecordWriterFactory mRecordWriterFactory;

  /**
   * Constructor.
   */
  @SuppressWarnings("rawtypes")
  public AvroKeyWithMetadataOutputFormat() {
    this(new RecordWriterFactory());
  }

  /**
   * Constructor.
   *
   * @param recordWriterFactory A factory for creating record writers.
   */
  protected AvroKeyWithMetadataOutputFormat(@SuppressWarnings("rawtypes") RecordWriterFactory recordWriterFactory) {
    mRecordWriterFactory = recordWriterFactory;
  }

  /**
   * A factory for creating record writers.
   *
   * @param  The java type of the avro record to write.
   */
  protected static class RecordWriterFactory {
    /**
     * Creates a new record writer instance.
     *
     * @param writerSchema The writer schema for the records to write.
     * @param compressionCodec The compression type for the writer file.
     * @param outputStream The target output stream for the records.
     */
    protected RecordWriter, NullWritable> create(
        Schema writerSchema, CodecFactory compressionCodec, OutputStream outputStream, Configuration conf)
        throws IOException {
      return new AvroKeyWithMetadataRecordWriter(writerSchema, compressionCodec, outputStream, conf);
    }
  }

  /** {@inheritDoc} */
  @Override
  @SuppressWarnings("unchecked")
  public RecordWriter, NullWritable> getRecordWriter(TaskAttemptContext context)
      throws IOException {
    // Get the writer schema.
    Schema writerSchema = AvroJob.getOutputKeySchema(context.getConfiguration());
    if (null == writerSchema) {
      throw new IOException(
          "AvroKeyOutputFormat requires an output schema. Use AvroJob.setOutputKeySchema().");
    }

    return mRecordWriterFactory.create(
        writerSchema, getCompressionCodec(context), getAvroFileOutputStream(context), context.getConfiguration());
  }
}