HadoopUtils.java

/**
 * Copyright 2016-2017 Seznam.cz, a.s.
 *
 * Licensed 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 cz.seznam.euphoria.hadoop;

import com.esotericsoftware.kryo.Kryo;
import com.esotericsoftware.kryo.Serializer;
import com.esotericsoftware.kryo.io.Input;
import com.esotericsoftware.kryo.io.Output;
import cz.seznam.euphoria.core.util.Settings;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.JobID;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.mapreduce.TaskType;
import org.apache.hadoop.mapreduce.task.JobContextImpl;
import org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl;
import org.objenesis.strategy.StdInstantiatorStrategy;

import java.io.ByteArrayOutputStream;
import java.net.URI;
import java.util.Map;

public class HadoopUtils {

  /**
   * Initialize Hadoop {@link Configuration} from Euphoria specific
   * {@link Settings} instance.
   *
   * @param settings euphoria's settings structure to create a hadoop
   *         configuration from
   *
   * @return a hadoop configuration reflecting the specified euphoria settings
   */
  public static Configuration createConfiguration(Settings settings) {
    Configuration conf = new Configuration();
    for (Map.Entry<String, String> c : settings.getAll().entrySet()) {
      conf.set(c.getKey(), c.getValue());
    }

    return conf;
  }

  public static <T> T instantiateHadoopFormat(
          Class<? extends T> cls,
          Class<T> superType,
          Configuration conf)
          throws InstantiationException, IllegalAccessException
  {
    if (!superType.isAssignableFrom(cls)) {
      throw new IllegalStateException(cls + " is not a sub-class of " + superType);
    }

    T inst = cls.newInstance();
    if (inst instanceof Configurable) {
      ((Configurable) inst).setConf(conf);
    }

    return inst;
  }

  public static JobContext createJobContext(Configuration conf) {
    // TODO jobId uses some default hard-coded value
    return new JobContextImpl(conf, new JobID("", 0));
  }

  public static TaskAttemptContext createTaskContext(Configuration conf,
                                                     int taskNumber)
  {
    // TODO uses some default hard-coded values
    TaskAttemptID taskAttemptID = new TaskAttemptID(
            "0", // job tracker ID
            0, // job number,
            TaskType.REDUCE, // task type,
            taskNumber, // task ID
            0); // task attempt
    return new TaskAttemptContextImpl(conf, taskAttemptID);
  }

  /**
   * Serialization helper to try serializing the given object into a byte array.
   * Deserialization is supposed to by handled via {@link #deserializeFromBytes(byte[])}.
   *
   * @param obj the object to be serialized
   *
   * @return the serialized object as a byte array; never {@code null}
   */
  public static byte[] serializeToBytes(Object obj) {
    Output baos = new Output(new ByteArrayOutputStream());
    newKryo().writeClassAndObject(baos, obj);
    return baos.toBytes();
  }

  /**
   * Serialization helper to deserialize the given byte array into an object
   * assuming that was serialized using {@link #serializeToBytes(Object)}.
   *
   * @param data the serialized form of a object
   *
   * @return the object deserialized from the given data bytes
   *
   * @throws RuntimeException if deserialization fails for some reason
   */
  public static Object deserializeFromBytes(byte [] data) {
    return newKryo().readClassAndObject(new Input(data));
  }

  static Kryo newKryo() {
    Kryo kryo = new Kryo();
    kryo.setInstantiatorStrategy(new StdInstantiatorStrategy());
    kryo.addDefaultSerializer(Path.class,  KryoPathSerializer.class);
    return kryo;
  }

  public static final class KryoPathSerializer extends Serializer<Path> {
    @Override
    public void write(Kryo kryo, Output output, Path object) {
      output.writeString(object.toUri().toString());
    }

    @Override
    public Path read(Kryo kryo, Input input, Class<Path> type) {
      return new Path(URI.create(input.readString()));
    }
  }
}