lang/java/mapred/src/main/java/org/apache/avro/mapred/AvroOutputFormat.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.avro.mapred;

import java.io.IOException;
import java.util.Map;
import java.net.URLDecoder;

import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.RecordWriter;
import org.apache.hadoop.util.Progressable;

import org.apache.avro.Schema;
import org.apache.avro.reflect.ReflectDatumWriter;
import org.apache.avro.file.DataFileWriter;
import org.apache.avro.file.CodecFactory;
import static org.apache.avro.file.DataFileConstants.DEFAULT_SYNC_INTERVAL;

/** An {@link org.apache.hadoop.mapred.OutputFormat} for Avro data files. */
public class AvroOutputFormat <T>
  extends FileOutputFormat<AvroWrapper<T>, NullWritable> {

  /** The file name extension for avro data files. */
  public final static String EXT = ".avro";

  /** The configuration key for Avro deflate level. */
  public static final String DEFLATE_LEVEL_KEY = "avro.mapred.deflate.level";

  /** The configuration key for Avro sync interval. */
  public static final String SYNC_INTERVAL_KEY = "avro.mapred.sync.interval";

  /** The default deflate level. */
  public static final int DEFAULT_DEFLATE_LEVEL = 1;

  /** Enable output compression using the deflate codec and specify its level.*/
  public static void setDeflateLevel(JobConf job, int level) {
    FileOutputFormat.setCompressOutput(job, true);
    job.setInt(DEFLATE_LEVEL_KEY, level);
  }

  /** Set the sync interval to be used by the underlying {@link DataFileWriter}.*/
  public static void setSyncInterval(JobConf job, int syncIntervalInBytes) {
    job.setInt(SYNC_INTERVAL_KEY, syncIntervalInBytes);
  }

  @Override
  public RecordWriter<AvroWrapper<T>, NullWritable>
    getRecordWriter(FileSystem ignore, JobConf job,
                    String name, Progressable prog)
    throws IOException {

    boolean isMapOnly = job.getNumReduceTasks() == 0;
    Schema schema = isMapOnly
      ? AvroJob.getMapOutputSchema(job)
      : AvroJob.getOutputSchema(job);

    final DataFileWriter<T> writer =
      new DataFileWriter<T>(new ReflectDatumWriter<T>());

    if (FileOutputFormat.getCompressOutput(job)) {
      int level = job.getInt(DEFLATE_LEVEL_KEY, DEFAULT_DEFLATE_LEVEL);
      writer.setCodec(CodecFactory.deflateCodec(level));
    }

    writer.setSyncInterval(job.getInt(SYNC_INTERVAL_KEY, DEFAULT_SYNC_INTERVAL));

    // copy metadata from job
    for (Map.Entry<String,String> e : job) {
      if (e.getKey().startsWith(AvroJob.TEXT_PREFIX))
        writer.setMeta(e.getKey().substring(AvroJob.TEXT_PREFIX.length()),
                       e.getValue());
      if (e.getKey().startsWith(AvroJob.BINARY_PREFIX))
        writer.setMeta(e.getKey().substring(AvroJob.BINARY_PREFIX.length()),
                       URLDecoder.decode(e.getValue(), "ISO-8859-1")
                       .getBytes("ISO-8859-1"));
    }

    Path path = FileOutputFormat.getTaskOutputPath(job, name+EXT);
    writer.create(schema, path.getFileSystem(job).create(path));

    return new RecordWriter<AvroWrapper<T>, NullWritable>() {
        public void write(AvroWrapper<T> wrapper, NullWritable ignore)
          throws IOException {
          writer.append(wrapper.datum());
        }
        public void close(Reporter reporter) throws IOException {
          writer.close();
        }
      };
  }

}