Java Job.getNumReduceTasks方法代碼示例

import org.apache.hadoop.mapreduce.Job; //導入方法依賴的package包/類
@Override
protected int configureNumReduceTasks(Job job) throws IOException {
  if (job.getNumReduceTasks() < 1) {
    job.setNumReduceTasks(1);
  }
  return job.getNumReduceTasks();
}
 

import org.apache.hadoop.mapreduce.Job; //導入方法依賴的package包/類
/**
 * Read in the partition file and build indexing data structures.
 * If the keytype is {@link org.apache.hadoop.io.BinaryComparable} and
 * <tt>total.order.partitioner.natural.order</tt> is not false, a trie
 * of the first <tt>total.order.partitioner.max.trie.depth</tt>(2) + 1 bytes
 * will be built. Otherwise, keys will be located using a binary search of
 * the partition keyset using the {@link org.apache.hadoop.io.RawComparator}
 * defined for this job. The input file must be sorted with the same
 * comparator and contain {@link Job#getNumReduceTasks()} - 1 keys.
 */
@SuppressWarnings("unchecked") // keytype from conf not static
public void setConf(Configuration conf) {
  try {
    this.conf = conf;
    String parts = getPartitionFile(conf);
    final Path partFile = new Path(parts);
    final FileSystem fs = (DEFAULT_PATH.equals(parts))
      ? FileSystem.getLocal(conf)     // assume in DistributedCache
      : partFile.getFileSystem(conf);

    Job job = Job.getInstance(conf);
    Class<K> keyClass = (Class<K>)job.getMapOutputKeyClass();
    K[] splitPoints = readPartitions(fs, partFile, keyClass, conf);
    if (splitPoints.length != job.getNumReduceTasks() - 1) {
      throw new IOException("Wrong number of partitions in keyset");
    }
    RawComparator<K> comparator =
      (RawComparator<K>) job.getSortComparator();
    for (int i = 0; i < splitPoints.length - 1; ++i) {
      if (comparator.compare(splitPoints[i], splitPoints[i+1]) >= 0) {
        throw new IOException("Split points are out of order");
      }
    }
    boolean natOrder =
      conf.getBoolean(NATURAL_ORDER, true);
    if (natOrder && BinaryComparable.class.isAssignableFrom(keyClass)) {
      partitions = buildTrie((BinaryComparable[])splitPoints, 0,
          splitPoints.length, new byte[0],
          // Now that blocks of identical splitless trie nodes are 
          // represented reentrantly, and we develop a leaf for any trie
          // node with only one split point, the only reason for a depth
          // limit is to refute stack overflow or bloat in the pathological
          // case where the split points are long and mostly look like bytes 
          // iii...iixii...iii   .  Therefore, we make the default depth
          // limit large but not huge.
          conf.getInt(MAX_TRIE_DEPTH, 200));
    } else {
      partitions = new BinarySearchNode(splitPoints, comparator);
    }
  } catch (IOException e) {
    throw new IllegalArgumentException("Can't read partitions file", e);
  }
}
 

import org.apache.hadoop.mapreduce.Job; //導入方法依賴的package包/類
/**
 * Write a partition file for the given job, using the Sampler provided.
 * Queries the sampler for a sample keyset, sorts by the output key
 * comparator, selects the keys for each rank, and writes to the destination
 * returned from {@link TotalOrderPartitioner#getPartitionFile}.
 */
@SuppressWarnings("unchecked") // getInputFormat, getOutputKeyComparator
public static <K,V> void writePartitionFile(Job job, Sampler<K,V> sampler) 
    throws IOException, ClassNotFoundException, InterruptedException {
  Configuration conf = job.getConfiguration();
  final InputFormat inf = 
      ReflectionUtils.newInstance(job.getInputFormatClass(), conf);
  int numPartitions = job.getNumReduceTasks();
  K[] samples = (K[])sampler.getSample(inf, job);
  LOG.info("Using " + samples.length + " samples");
  RawComparator<K> comparator =
    (RawComparator<K>) job.getSortComparator();
  Arrays.sort(samples, comparator);
  Path dst = new Path(TotalOrderPartitioner.getPartitionFile(conf));
  FileSystem fs = dst.getFileSystem(conf);
  if (fs.exists(dst)) {
    fs.delete(dst, false);
  }
  SequenceFile.Writer writer = SequenceFile.createWriter(fs, 
    conf, dst, job.getMapOutputKeyClass(), NullWritable.class);
  NullWritable nullValue = NullWritable.get();
  float stepSize = samples.length / (float) numPartitions;
  int last = -1;
  for(int i = 1; i < numPartitions; ++i) {
    int k = Math.round(stepSize * i);
    while (last >= k && comparator.compare(samples[last], samples[k]) == 0) {
      ++k;
    }
    writer.append(samples[k], nullValue);
    last = k;
  }
  writer.close();
}
 

import org.apache.hadoop.mapreduce.Job; //導入方法依賴的package包/類
/**
 * Use this before submitting a TableReduce job. It will
 * appropriately set up the JobConf.
 *
 * @param table  The output table.
 * @param reducer  The reducer class to use.
 * @param job  The current job to adjust.  Make sure the passed job is
 * carrying all necessary HBase configuration.
 * @param partitioner  Partitioner to use. Pass <code>null</code> to use
 * default partitioner.
 * @param quorumAddress Distant cluster to write to; default is null for
 * output to the cluster that is designated in <code>hbase-site.xml</code>.
 * Set this String to the zookeeper ensemble of an alternate remote cluster
 * when you would have the reduce write a cluster that is other than the
 * default; e.g. copying tables between clusters, the source would be
 * designated by <code>hbase-site.xml</code> and this param would have the
 * ensemble address of the remote cluster.  The format to pass is particular.
 * Pass <code> &lt;hbase.zookeeper.quorum&gt;:&lt;
 *             hbase.zookeeper.client.port&gt;:&lt;zookeeper.znode.parent&gt;
 * </code> such as <code>server,server2,server3:2181:/hbase</code>.
 * @param serverClass redefined hbase.regionserver.class
 * @param serverImpl redefined hbase.regionserver.impl
 * @param addDependencyJars upload HBase jars and jars for any of the configured
 *           job classes via the distributed cache (tmpjars).
 * @throws IOException When determining the region count fails.
 */
public static void initTableReducerJob(String table,
  Class<? extends TableReducer> reducer, Job job,
  Class partitioner, String quorumAddress, String serverClass,
  String serverImpl, boolean addDependencyJars) throws IOException {

  Configuration conf = job.getConfiguration();
  HBaseConfiguration.merge(conf, HBaseConfiguration.create(conf));
  job.setOutputFormatClass(TableOutputFormat.class);
  if (reducer != null) job.setReducerClass(reducer);
  conf.set(TableOutputFormat.OUTPUT_TABLE, table);
  conf.setStrings("io.serializations", conf.get("io.serializations"),
      MutationSerialization.class.getName(), ResultSerialization.class.getName());
  // If passed a quorum/ensemble address, pass it on to TableOutputFormat.
  if (quorumAddress != null) {
    // Calling this will validate the format
    ZKConfig.validateClusterKey(quorumAddress);
    conf.set(TableOutputFormat.QUORUM_ADDRESS,quorumAddress);
  }
  if (serverClass != null && serverImpl != null) {
    conf.set(TableOutputFormat.REGION_SERVER_CLASS, serverClass);
    conf.set(TableOutputFormat.REGION_SERVER_IMPL, serverImpl);
  }
  job.setOutputKeyClass(ImmutableBytesWritable.class);
  job.setOutputValueClass(Writable.class);
  if (partitioner == HRegionPartitioner.class) {
    job.setPartitionerClass(HRegionPartitioner.class);
    int regions = MetaTableAccessor.getRegionCount(conf, TableName.valueOf(table));
    if (job.getNumReduceTasks() > regions) {
      job.setNumReduceTasks(regions);
    }
  } else if (partitioner != null) {
    job.setPartitionerClass(partitioner);
  }

  if (addDependencyJars) {
    addDependencyJars(job);
  }

  initCredentials(job);
}
 

import org.apache.hadoop.mapreduce.Job; //導入方法依賴的package包/類
/**
 * Ensures that the given number of reduce tasks for the given job
 * configuration does not exceed the number of regions for the given table.
 *
 * @param table  The table to get the region count for.
 * @param job  The current job to adjust.
 * @throws IOException When retrieving the table details fails.
 */
public static void limitNumReduceTasks(String table, Job job)
throws IOException {
  int regions =
    MetaTableAccessor.getRegionCount(job.getConfiguration(), TableName.valueOf(table));
  if (job.getNumReduceTasks() > regions)
    job.setNumReduceTasks(regions);
}