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From: pwendell <git@git.apache.org>
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Subject: [GitHub] spark pull request: [SPARK-3543] Write TaskContext in Java
 and exp...
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Message-Id: <20140921012527.359AEA1D9E8@tyr.zones.apache.org>
Date: Sun, 21 Sep 2014 01:25:27 +0000 (UTC)

Github user pwendell commented on a diff in the pull request:

    https://github.com/apache/spark/pull/2425#discussion_r17822735
  
    --- Diff: core/src/main/java/org/apache/spark/TaskContext.java ---
    @@ -0,0 +1,238 @@
    +/*
    + * 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.spark;
    +
    +import java.io.Serializable;
    +import java.util.ArrayList;
    +import java.util.Collections;
    +import java.util.List;
    +
    +import scala.Function0;
    +import scala.Function1;
    +import scala.Unit;
    +import scala.collection.JavaConversions;
    +
    +import org.apache.spark.annotation.DeveloperApi;
    +import org.apache.spark.executor.TaskMetrics;
    +import org.apache.spark.util.TaskCompletionListener;
    +import org.apache.spark.util.TaskCompletionListenerException;
    +
    +/**
    +* :: DeveloperApi ::
    +* Contextual information about a task which can be read or mutated during execution.
    +*/
    +@DeveloperApi
    +public class TaskContext implements Serializable {
    +
    +  private int stageId;
    +  private int partitionId;
    +  private long attemptId;
    +  private boolean runningLocally;
    +  private TaskMetrics taskMetrics;
    +
    +  /**
    +   * :: DeveloperApi ::
    +   * Contextual information about a task which can be read or mutated during execution.
    +   *
    +   * @param stageId stage id
    +   * @param partitionId index of the partition
    +   * @param attemptId the number of attempts to execute this task
    +   * @param runningLocally whether the task is running locally in the driver JVM
    +   * @param taskMetrics performance metrics of the task
    +   */
    +  @DeveloperApi
    +  public TaskContext(Integer stageId, Integer partitionId, Long attemptId, Boolean runningLocally,
    +                     TaskMetrics taskMetrics) {
    +    this.attemptId = attemptId;
    +    this.partitionId = partitionId;
    +    this.runningLocally = runningLocally;
    +    this.stageId = stageId;
    +    this.taskMetrics = taskMetrics;
    +  }
    +
    +
    +  /**
    +   * :: DeveloperApi ::
    +   * Contextual information about a task which can be read or mutated during execution.
    +   *
    +   * @param stageId stage id
    +   * @param partitionId index of the partition
    +   * @param attemptId the number of attempts to execute this task
    +   * @param runningLocally whether the task is running locally in the driver JVM
    +   */
    +  @DeveloperApi
    +  public TaskContext(Integer stageId, Integer partitionId, Long attemptId,
    +                     Boolean runningLocally) {
    +    this.attemptId = attemptId;
    +    this.partitionId = partitionId;
    +    this.runningLocally = runningLocally;
    +    this.stageId = stageId;
    +    this.taskMetrics = TaskMetrics.empty();
    +  }
    +
    +
    +  /**
    +   * :: DeveloperApi ::
    +   * Contextual information about a task which can be read or mutated during execution.
    +   *
    +   * @param stageId stage id
    +   * @param partitionId index of the partition
    +   * @param attemptId the number of attempts to execute this task
    +   */
    +  @DeveloperApi
    +  public TaskContext(Integer stageId, Integer partitionId, Long attemptId) {
    +    this.attemptId = attemptId;
    +    this.partitionId = partitionId;
    +    this.runningLocally = false;
    +    this.stageId = stageId;
    +    this.taskMetrics = TaskMetrics.empty();
    +  }
    +
    +  private static ThreadLocal<TaskContext> taskContext =
    +    new ThreadLocal<TaskContext>();
    +
    +  public static void setTaskContext(TaskContext tc) {
    +    taskContext.set(tc);
    +  }
    +
    +  public static TaskContext get() {
    +    return taskContext.get();
    +  }
    +
    +  // List of callback functions to execute when the task completes.
    +  private transient List<TaskCompletionListener> onCompleteCallbacks =
    +    new ArrayList<TaskCompletionListener>();
    +
    +  // Whether the corresponding task has been killed.
    +  private volatile Boolean interrupted = false;
    +
    +  // Whether the task has completed.
    +  private volatile Boolean completed = false;
    +
    +  /**
    +   * Checks whether the task has completed.
    +   */
    +  public Boolean isCompleted() {
    +    return completed;
    +  }
    +
    +  /**
    +   * Checks whether the task has been killed.
    +   */
    +  public Boolean isInterrupted() {
    +    return interrupted;
    +  }
    +
    +  /**
    +   * Add a (Java friendly) listener to be executed on task completion.
    +   * This will be called in all situation - success, failure, or cancellation.
    +   * <p/>
    +   * An example use is for HadoopRDD to register a callback to close the input stream.
    +   */
    +  public TaskContext addTaskCompletionListener(TaskCompletionListener listener) {
    +    onCompleteCallbacks.add(listener);
    +    return this;
    +  }
    +
    +  /**
    +   * Add a listener in the form of a Scala closure to be executed on task completion.
    +   * This will be called in all situation - success, failure, or cancellation.
    +   * <p/>
    +   * An example use is for HadoopRDD to register a callback to close the input stream.
    +   */
    +  public TaskContext addTaskCompletionListener(final Function1<TaskContext, Unit> f) {
    +    onCompleteCallbacks.add(new TaskCompletionListener() {
    +      @Override
    +      public void onTaskCompletion(TaskContext context) {
    +        f.apply(context);
    +      }
    +    });
    +    return this;
    +  }
    +
    +  /**
    +   * Add a callback function to be executed on task completion. An example use
    +   * is for HadoopRDD to register a callback to close the input stream.
    +   * Will be called in any situation - success, failure, or cancellation.
    +   *
    +   * @param f Callback function.
    +   */
    +  @Deprecated
    +  public void addOnCompleteCallback(final Function0<Unit> f) {
    +    onCompleteCallbacks.add(new TaskCompletionListener() {
    +      @Override
    +      public void onTaskCompletion(TaskContext context) {
    +        f.apply();
    +      }
    +    });
    +  }
    +
    +  /**
    +   * ::Internal API::
    +   * Marks the task as completed and triggers the listeners.
    +   */
    +  public void markTaskCompleted() throws TaskCompletionListenerException {
    +    completed = true;
    +    List<String> errorMsgs = new ArrayList<String>(2);
    +    // Process complete callbacks in the reverse order of registration
    +    List<TaskCompletionListener> revlist =
    +      new ArrayList<TaskCompletionListener>(onCompleteCallbacks);
    +    Collections.reverse(revlist);
    +    for (TaskCompletionListener tcl : revlist) {
    +      try {
    +        tcl.onTaskCompletion(this);
    +      } catch (Throwable e) {
    +        errorMsgs.add(e.getMessage());
    +      }
    +    }
    +
    +    if (!errorMsgs.isEmpty()) {
    +      throw new TaskCompletionListenerException(JavaConversions.asScalaBuffer(errorMsgs));
    +    }
    +    taskContext.remove();
    +  }
    +
    +  /**
    +   * ::Internal API::
    +   * Marks the task for interruption, i.e. cancellation.
    +   */
    +  public void markInterrupted() {
    +    interrupted = true;
    +  }
    +
    +  public int stageId() {
    --- End diff --
    
    In the future I think we'll use standard "Java Bean" getters for most classes we expose like this. I think it might be good to add these (`getStageId`, `getPartitionId`). We can keep the current ones for compatiblity (`stageId`) and deprecate them in favor of the new ones.


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