Java tutorial
/** * 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.hadoop.mapreduce; import java.io.DataInput; import java.io.DataOutput; import java.io.IOException; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; /** * TaskAttemptID represents the immutable and unique identifier for * a task attempt. Each task attempt is one particular instance of a Map or * Reduce Task identified by its TaskID. * * TaskAttemptID consists of 2 parts. First part is the * {@link TaskID}, that this TaskAttemptID belongs to. * Second part is the task attempt number. <br> * An example TaskAttemptID is : * <code>attempt_200707121733_0003_m_000005_0</code> , which represents the * zeroth task attempt for the fifth map task in the third job * running at the jobtracker started at <code>200707121733</code>. * <p> * Applications should never construct or parse TaskAttemptID strings * , but rather use appropriate constructors or {@link #forName(String)} * method. * * @see JobID * @see TaskID */ @InterfaceAudience.Public @InterfaceStability.Stable public class TaskAttemptID extends org.apache.hadoop.mapred.ID { protected static final String ATTEMPT = "attempt"; private TaskID taskId; /** * Constructs a TaskAttemptID object from given {@link TaskID}. * @param taskId TaskID that this task belongs to * @param id the task attempt number */ public TaskAttemptID(TaskID taskId, int id) { super(id); if (taskId == null) { throw new IllegalArgumentException("taskId cannot be null"); } this.taskId = taskId; } /** * Constructs a TaskId object from given parts. * @param jtIdentifier jobTracker identifier * @param jobId job number * @param type the TaskType * @param taskId taskId number * @param id the task attempt number */ public TaskAttemptID(String jtIdentifier, int jobId, TaskType type, int taskId, int id) { this(new TaskID(jtIdentifier, jobId, type, taskId), id); } /** * Constructs a TaskId object from given parts. * @param jtIdentifier jobTracker identifier * @param jobId job number * @param isMap whether the tip is a map * @param taskId taskId number * @param id the task attempt number */ @Deprecated public TaskAttemptID(String jtIdentifier, int jobId, boolean isMap, int taskId, int id) { this(new TaskID(jtIdentifier, jobId, isMap, taskId), id); } public TaskAttemptID() { taskId = new TaskID(); } /** Returns the {@link JobID} object that this task attempt belongs to */ public JobID getJobID() { return taskId.getJobID(); } /** Returns the {@link TaskID} object that this task attempt belongs to */ public TaskID getTaskID() { return taskId; } /**Returns whether this TaskID is a map ID */ @Deprecated public boolean isMap() { return taskId.isMap(); } /**Returns the TaskType of the TaskAttemptID */ public TaskType getTaskType() { return taskId.getTaskType(); } @Override public boolean equals(Object o) { if (!super.equals(o)) return false; TaskAttemptID that = (TaskAttemptID) o; return this.taskId.equals(that.taskId); } /** * Add the unique string to the StringBuilder * @param builder the builder to append ot * @return the builder that was passed in. */ protected StringBuilder appendTo(StringBuilder builder) { return taskId.appendTo(builder).append(SEPARATOR).append(id); } @Override public void readFields(DataInput in) throws IOException { super.readFields(in); taskId.readFields(in); } @Override public void write(DataOutput out) throws IOException { super.write(out); taskId.write(out); } @Override public int hashCode() { return taskId.hashCode() * 5 + id; } /**Compare TaskIds by first tipIds, then by task numbers. */ @Override public int compareTo(ID o) { TaskAttemptID that = (TaskAttemptID) o; int tipComp = this.taskId.compareTo(that.taskId); if (tipComp == 0) { return this.id - that.id; } else return tipComp; } @Override public String toString() { return appendTo(new StringBuilder(ATTEMPT)).toString(); } /** Construct a TaskAttemptID object from given string * @return constructed TaskAttemptID object or null if the given String is null * @throws IllegalArgumentException if the given string is malformed */ public static TaskAttemptID forName(String str) throws IllegalArgumentException { if (str == null) return null; String exceptionMsg = null; try { String[] parts = str.split(Character.toString(SEPARATOR)); if (parts.length == 6) { if (parts[0].equals(ATTEMPT)) { String type = parts[3]; TaskType t = TaskID.getTaskType(type.charAt(0)); if (t != null) { return new org.apache.hadoop.mapred.TaskAttemptID(parts[1], Integer.parseInt(parts[2]), t, Integer.parseInt(parts[4]), Integer.parseInt(parts[5])); } else exceptionMsg = "Bad TaskType identifier. TaskAttemptId string : " + str + " is not properly formed."; } } } catch (Exception ex) { //fall below } if (exceptionMsg == null) { exceptionMsg = "TaskAttemptId string : " + str + " is not properly formed"; } throw new IllegalArgumentException(exceptionMsg); } }