src/java/org/apache/nutch/fetcher/FetcherOutputFormat.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.nutch.fetcher;

import java.io.IOException;

import org.apache.nutch.crawl.CrawlDatum;
import org.apache.nutch.crawl.NutchWritable;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.MapFile;
import org.apache.hadoop.io.MapFile.Writer.Option;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.SequenceFile.CompressionType;
import org.apache.hadoop.util.Progressable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapred.InvalidJobConfException;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.nutch.parse.Parse;
import org.apache.nutch.parse.ParseOutputFormat;
import org.apache.nutch.protocol.Content;

/** Splits FetcherOutput entries into multiple map files. */
public class FetcherOutputFormat extends FileOutputFormat<Text, NutchWritable> {

  @Override
  public void checkOutputSpecs(JobContext job) throws IOException {
    Configuration conf = job.getConfiguration();
    Path out = FileOutputFormat.getOutputPath(job);
    if ((out == null) && (job.getNumReduceTasks() != 0)) {
      throw new InvalidJobConfException("Output directory not set in conf.");
    }
    FileSystem fs = out.getFileSystem(conf);
    if (fs.exists(new Path(out, CrawlDatum.FETCH_DIR_NAME))) {
      throw new IOException("Segment already fetched!");
    }
  }

  @Override
  public RecordWriter<Text, NutchWritable> getRecordWriter(TaskAttemptContext context)
          throws IOException {

    Configuration conf = context.getConfiguration();
    String name = getUniqueFile(context, "part", "");
    Path out = FileOutputFormat.getOutputPath(context);
    final Path fetch = new Path(new Path(out, CrawlDatum.FETCH_DIR_NAME), name);
    final Path content = new Path(new Path(out, Content.DIR_NAME), name);

    final CompressionType compType = SequenceFileOutputFormat
        .getOutputCompressionType(context);

    Option fKeyClassOpt = MapFile.Writer.keyClass(Text.class);
    org.apache.hadoop.io.SequenceFile.Writer.Option fValClassOpt = SequenceFile.Writer.valueClass(CrawlDatum.class);
    org.apache.hadoop.io.SequenceFile.Writer.Option fProgressOpt = SequenceFile.Writer.progressable((Progressable)context);
    org.apache.hadoop.io.SequenceFile.Writer.Option fCompOpt = SequenceFile.Writer.compression(compType);

    final MapFile.Writer fetchOut = new MapFile.Writer(conf,
        fetch, fKeyClassOpt, fValClassOpt, fCompOpt, fProgressOpt);

    return new RecordWriter<Text, NutchWritable>() {
      private MapFile.Writer contentOut;
      private RecordWriter<Text, Parse> parseOut;

      {
        if (Fetcher.isStoringContent(conf)) {
          Option cKeyClassOpt = MapFile.Writer.keyClass(Text.class);
          org.apache.hadoop.io.SequenceFile.Writer.Option cValClassOpt = SequenceFile.Writer.valueClass(Content.class);
          org.apache.hadoop.io.SequenceFile.Writer.Option cProgressOpt = SequenceFile.Writer.progressable((Progressable)context);
          org.apache.hadoop.io.SequenceFile.Writer.Option cCompOpt = SequenceFile.Writer.compression(compType);
          contentOut = new MapFile.Writer(conf, content,
              cKeyClassOpt, cValClassOpt, cCompOpt, cProgressOpt);
        }

        if (Fetcher.isParsing(conf)) {
          parseOut = new ParseOutputFormat().getRecordWriter(context);
        }
      }

      public void write(Text key, NutchWritable value) throws IOException, InterruptedException {

        Writable w = value.get();

        if (w instanceof CrawlDatum)
          fetchOut.append(key, w);
        else if (w instanceof Content && contentOut != null)
          contentOut.append(key, w);
        else if (w instanceof Parse && parseOut != null)
          parseOut.write(key, (Parse) w);
      }

      public void close(TaskAttemptContext context) throws IOException, InterruptedException {
        fetchOut.close();
        if (contentOut != null) {
          contentOut.close();
        }
        if (parseOut != null) {
          parseOut.close(context);
        }
      }

    };

  }
}