indexer/src/main/java/com/metamx/druid/indexer/Utils.java

/*
 * Druid - a distributed column store.
 * Copyright (C) 2012  Metamarkets Group Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

package com.metamx.druid.indexer;

import com.google.common.base.Preconditions;
import com.google.common.collect.Iterators;
import com.metamx.common.ISE;
import com.metamx.druid.jackson.DefaultObjectMapper;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.GzipCodec;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.ReflectionUtils;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 */
public class Utils
{
  private static final ObjectMapper jsonMapper = new DefaultObjectMapper();

  public static <K, V> Map<K, V> zipMap(Iterable<K> keys, Iterable<V> values)
  {
    Map<K, V> retVal = new HashMap<K, V>();

    Iterator<K> keyIter = keys.iterator();
    Iterator<V> valsIter = values.iterator();
    while (keyIter.hasNext()) {
      final K key = keyIter.next();

      Preconditions.checkArgument(valsIter.hasNext(), "keys longer than vals, bad, bad vals.  Broke on key[%s]", key);
      retVal.put(key, valsIter.next());
    }
    if (valsIter.hasNext()) {
      throw new ISE("More values[%d] than keys[%d]", retVal.size() + Iterators.size(valsIter), retVal.size());
    }

    return retVal;
  }

  public static OutputStream makePathAndOutputStream(JobContext job, Path outputPath, boolean deleteExisting) throws IOException
  {
    OutputStream retVal;
    FileSystem fs = outputPath.getFileSystem(job.getConfiguration());

    if (fs.exists(outputPath)) {
      if (deleteExisting) {
        fs.delete(outputPath, false);
      }
      else {
        throw new ISE("outputPath[%s] must not exist.", outputPath);
      }
    }

    if (!FileOutputFormat.getCompressOutput(job)) {
      retVal = fs.create(outputPath, false);
    } else {
      Class<? extends CompressionCodec> codecClass = FileOutputFormat.getOutputCompressorClass(job, GzipCodec.class);
      CompressionCodec codec = ReflectionUtils.newInstance(codecClass, job.getConfiguration());
      outputPath = new Path(outputPath.toString() + codec.getDefaultExtension());

      retVal = codec.createOutputStream(fs.create(outputPath, false));
    }

    return retVal;
  }

  public static InputStream openInputStream(JobContext job, Path inputPath) throws IOException
  {
    return openInputStream(inputPath, inputPath.getFileSystem(job.getConfiguration()));
  }

  public static InputStream openInputStream(Path inputPath, final FileSystem fileSystem) throws IOException
  {
    return fileSystem.open(inputPath);
  }

  public static Map<String, Object> getStats(JobContext job, Path statsPath)
      throws IOException
  {
    FileSystem fs = statsPath.getFileSystem(job.getConfiguration());

    return jsonMapper.readValue(
        fs.open(statsPath),
        new TypeReference<Map<String, Object>>(){}
    );
  }

  public static void storeStats(
      JobContext job, Path path, Map<String, Object> stats
  ) throws IOException
  {
    jsonMapper.writeValue(
        makePathAndOutputStream(job, path, true),
        stats
    );
  }
}