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.mapred; import java.io.DataInput; import java.io.IOException; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; import org.apache.hadoop.mapreduce.TaskType; /** * TaskID represents the immutable and unique identifier for * a Map or Reduce Task. Each TaskID encompasses multiple attempts made to * execute the Map or Reduce Task, each of which are uniquely indentified by * their TaskAttemptID. * * TaskID consists of 3 parts. First part is the {@link JobID}, that this * TaskInProgress belongs to. Second part of the TaskID is either 'm' or 'r' * representing whether the task is a map task or a reduce task. * And the third part is the task number. <br> * An example TaskID is : * <code>task_200707121733_0003_m_000005</code> , which represents the * fifth map task in the third job running at the jobtracker * started at <code>200707121733</code>. * <p> * Applications should never construct or parse TaskID strings * , but rather use appropriate constructors or {@link #forName(String)} * method. * * @see JobID * @see TaskAttemptID */ @InterfaceAudience.Public @InterfaceStability.Stable public class TaskID extends org.apache.hadoop.mapreduce.TaskID { /** * Constructs a TaskID object from given {@link JobID}. * @param jobId JobID that this tip belongs to * @param isMap whether the tip is a map * @param id the tip number * @deprecated Use {@link #TaskID(String, int, TaskType, int)} */ @Deprecated public TaskID(org.apache.hadoop.mapreduce.JobID jobId, boolean isMap, int id) { this(jobId, isMap ? TaskType.MAP : TaskType.REDUCE, id); } /** * Constructs a TaskInProgressId object from given parts. * @param jtIdentifier jobTracker identifier * @param jobId job number * @param isMap whether the tip is a map * @param id the tip number * @deprecated Use {@link #TaskID(org.apache.hadoop.mapreduce.JobID, TaskType, * int)} */ @Deprecated public TaskID(String jtIdentifier, int jobId, boolean isMap, int id) { this(jtIdentifier, jobId, isMap ? TaskType.MAP : TaskType.REDUCE, id); } /** * Constructs a TaskID object from given {@link JobID}. * @param jobId JobID that this tip belongs to * @param type the {@link TaskType} * @param id the tip number */ public TaskID(org.apache.hadoop.mapreduce.JobID jobId, TaskType type, int id) { super(jobId, type, id); } /** * Constructs a TaskInProgressId object from given parts. * @param jtIdentifier jobTracker identifier * @param jobId job number * @param type the {@link TaskType} * @param id the tip number */ public TaskID(String jtIdentifier, int jobId, TaskType type, int id) { this(new JobID(jtIdentifier, jobId), type, id); } public TaskID() { super(new JobID(), TaskType.REDUCE, 0); } /** * Downgrade a new TaskID to an old one * @param old a new or old TaskID * @return either old or a new TaskID build to match old */ public static TaskID downgrade(org.apache.hadoop.mapreduce.TaskID old) { if (old instanceof TaskID) { return (TaskID) old; } else { return new TaskID(JobID.downgrade(old.getJobID()), old.getTaskType(), old.getId()); } } @Deprecated public static TaskID read(DataInput in) throws IOException { TaskID tipId = new TaskID(); tipId.readFields(in); return tipId; } public JobID getJobID() { return (JobID) super.getJobID(); } /** * Returns a regex pattern which matches task IDs. Arguments can * be given null, in which case that part of the regex will be generic. * For example to obtain a regex matching <i>the first map task</i> * of <i>any jobtracker</i>, of <i>any job</i>, we would use : * <pre> * TaskID.getTaskIDsPattern(null, null, true, 1); * </pre> * which will return : * <pre> "task_[^_]*_[0-9]*_m_000001*" </pre> * @param jtIdentifier jobTracker identifier, or null * @param jobId job number, or null * @param isMap whether the tip is a map, or null * @param taskId taskId number, or null * @return a regex pattern matching TaskIDs * @deprecated Use {@link TaskID#getTaskIDsPattern(String, Integer, TaskType, * Integer)} */ @Deprecated public static String getTaskIDsPattern(String jtIdentifier, Integer jobId, Boolean isMap, Integer taskId) { return getTaskIDsPattern(jtIdentifier, jobId, isMap ? TaskType.MAP : TaskType.REDUCE, taskId); } /** * Returns a regex pattern which matches task IDs. Arguments can * be given null, in which case that part of the regex will be generic. * For example to obtain a regex matching <i>the first map task</i> * of <i>any jobtracker</i>, of <i>any job</i>, we would use : * <pre> * TaskID.getTaskIDsPattern(null, null, true, 1); * </pre> * which will return : * <pre> "task_[^_]*_[0-9]*_m_000001*" </pre> * @param jtIdentifier jobTracker identifier, or null * @param jobId job number, or null * @param type the {@link TaskType}, or null * @param taskId taskId number, or null * @return a regex pattern matching TaskIDs */ @Deprecated public static String getTaskIDsPattern(String jtIdentifier, Integer jobId, TaskType type, Integer taskId) { StringBuilder builder = new StringBuilder(TASK).append(SEPARATOR) .append(getTaskIDsPatternWOPrefix(jtIdentifier, jobId, type, taskId)); return builder.toString(); } @Deprecated static StringBuilder getTaskIDsPatternWOPrefix(String jtIdentifier, Integer jobId, TaskType type, Integer taskId) { StringBuilder builder = new StringBuilder(); builder.append(JobID.getJobIDsPatternWOPrefix(jtIdentifier, jobId)).append(SEPARATOR) .append(type != null ? (org.apache.hadoop.mapreduce.TaskID.getRepresentingCharacter(type)) : org.apache.hadoop.mapreduce.TaskID.getAllTaskTypes()) .append(SEPARATOR).append(taskId != null ? idFormat.format(taskId) : "[0-9]*"); return builder; } public static TaskID forName(String str) throws IllegalArgumentException { return (TaskID) org.apache.hadoop.mapreduce.TaskID.forName(str); } }