content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.job.plan;
  
  import alluxio.collections.Pair;
  import alluxio.job.JobConfig;
  import alluxio.job.RunTaskContext;
  import alluxio.job.SelectExecutorsContext;
  import alluxio.wire.WorkerInfo;
  
  import java.io.Serializable;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * A job definition. A definition has two important parts: (1) a
   * {@link PlanDefinition#selectExecutors(JobConfig, List, SelectExecutorsContext)} method runs at
   * the master node and selects the workers to run the executors.
   * (2) a {@link #runTask(JobConfig, Serializable, RunTaskContext)} method runs at each selected
   * executor on the worker node.
   *
   * @param <T> the job configuration
   * @param <P> the parameters to pass to each task
   * @param <R> the return type from the task
   */
  public interface PlanDefinition<T extends JobConfig, P extends Serializable,
      R extends Serializable> {
    /**
     * @return the class of the associated {@link JobConfig}
     */
    Class<T> getJobConfigClass();
  
    /**
     * Selects the workers to run the task.
     *
     * @param config the job configuration
     * @param jobWorkerInfoList the list of available workers' information
     * @param selectExecutorsContext the context containing information used to select executors
     * @return a set of pairs of selected workers to the parameters to pass along
     * @throws Exception if any error occurs
     */
    Set<Pair<WorkerInfo, P>> selectExecutors(T config, List<WorkerInfo> jobWorkerInfoList,
        SelectExecutorsContext selectExecutorsContext) throws Exception;
  
    /**
     * Runs the task in the executor.
     *
     * @param config the job configuration
     * @param args the arguments passed in
     * @param runTaskContext the context containing information used to execute a task
     * @return the task result
     * @throws Exception if any error occurs
     */
    R runTask(T config, P args, RunTaskContext runTaskContext) throws Exception;
  
    /**
     * Joins the task results on the master.
     *
     * @param config the job configuration
     * @param taskResults the task results
     * @return the joined results
     * @throws Exception if any error occurs
     */
    String join(T config, Map<WorkerInfo, R> taskResults) throws Exception;
  }
  