/*
 * 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.reef.task;

import org.apache.reef.annotations.audience.Public;
import org.apache.reef.annotations.audience.TaskSide;

/**
 * The interface for Tasks.
 * <p>
 * This interface is to be implemented for Tasks.
 * <p>
 * The main entry point for a Task is the call() method inherited from
 * {@link java.util.concurrent.Callable}. The REEF Evaluator will call this method in order to run
 * the Task. The byte[] returned by it will be pushed to the Job Driver.
 */
@TaskSide
@Public
public interface Task {

  /**
   * Called by the resourcemanager harness to execute the task.
   *
   * @param memento the memento objected passed down by the driver.
   * @return the user defined return value
   * @throws Exception whenever the Task encounters an unsolved issue.
   *                   This Exception will be thrown at the Driver's event handler.
   */
  byte[] call(final byte[] memento) throws Exception;
}