TaskID.java
/**
* 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 java.text.NumberFormat;
import java.util.EnumMap;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.WritableUtils;
/**
* 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.mapred.ID {
protected static final String TASK = "task";
protected static final NumberFormat idFormat = NumberFormat.getInstance();
public static final String TASK_ID_REGEX = TASK + "_(\\d+)_(\\d+)_" +
CharTaskTypeMaps.allTaskTypes + "_(\\d+)";
public static final Pattern taskIdPattern = Pattern.compile(TASK_ID_REGEX);
static {
idFormat.setGroupingUsed(false);
idFormat.setMinimumIntegerDigits(6);
}
private JobID jobId;
private TaskType type;
/**
* Constructs a TaskID object from given {@link JobID}.
*
* @param jobId JobID that this tip belongs to
* @param type the {@link TaskType} of the task
* @param id the tip number
*/
public TaskID(JobID jobId, TaskType type, int id) {
super(id);
if(jobId == null) {
throw new IllegalArgumentException("jobId cannot be null");
}
this.jobId = jobId;
this.type = type;
}
/**
* Constructs a TaskInProgressId object from given parts.
*
* @param jtIdentifier jobTracker identifier
* @param jobId job number
* @param type the TaskType
* @param id the tip number
*/
public TaskID(String jtIdentifier, int jobId, TaskType type, int id) {
this(new JobID(jtIdentifier, jobId), type, id);
}
/**
* 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
public TaskID(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
public TaskID(String jtIdentifier, int jobId, boolean isMap, int id) {
this(new JobID(jtIdentifier, jobId), isMap, id);
}
/**
* Default constructor for Writable. Sets the task type to
* {@link TaskType#REDUCE}, the ID to 0, and the job ID to an empty job ID.
*/
public TaskID() {
this(new JobID(), TaskType.REDUCE, 0);
}
/**
* Returns the {@link JobID} object that this tip belongs to.
*
* @return the JobID object
*/
public JobID getJobID() {
return jobId;
}
/**
* Returns whether this TaskID is a map ID.
*
* @return whether this TaskID is a map ID
*/
@Deprecated
public boolean isMap() {
return type == TaskType.MAP;
}
/**
* Get the type of the task.
*
* @return the type of the task
*/
public TaskType getTaskType() {
return type;
}
@Override
public boolean equals(Object o) {
if (!super.equals(o))
return false;
TaskID that = (TaskID)o;
return this.type == that.type && this.jobId.equals(that.jobId);
}
/**
* Compare TaskInProgressIds by first jobIds, then by tip numbers.
* Reducers are defined as greater than mappers.
*
* @param o the TaskID against which to compare
* @return 0 if equal, positive if this TaskID is greater, and negative if
* this TaskID is less
*/
@Override
public int compareTo(ID o) {
TaskID that = (TaskID)o;
int jobComp = this.jobId.compareTo(that.jobId);
if(jobComp == 0) {
if(this.type == that.type) {
return this.id - that.id;
}
else {
return this.type.compareTo(that.type);
}
}
else return jobComp;
}
@Override
public String toString() {
return appendTo(new StringBuilder(TASK)).toString();
}
/**
* Add the unique string to the given builder.
*
* @param builder the builder to append to
* @return the builder that was passed in
*/
protected StringBuilder appendTo(StringBuilder builder) {
return jobId.appendTo(builder).
append(SEPARATOR).
append(CharTaskTypeMaps.getRepresentingCharacter(type)).
append(SEPARATOR).
append(idFormat.format(id));
}
@Override
public int hashCode() {
return jobId.hashCode() * 524287 + id;
}
@Override
public void readFields(DataInput in) throws IOException {
super.readFields(in);
jobId.readFields(in);
type = WritableUtils.readEnum(in, TaskType.class);
}
@Override
public void write(DataOutput out) throws IOException {
super.write(out);
jobId.write(out);
WritableUtils.writeEnum(out, type);
}
/**
* Construct a TaskID object from given string.
*
* @param str the target string
* @return constructed TaskID object or null if the given String is null
* @throws IllegalArgumentException if the given string is malformed
*/
public static TaskID forName(String str)
throws IllegalArgumentException {
if(str == null)
return null;
Matcher m = taskIdPattern.matcher(str);
if (m.matches()) {
return new org.apache.hadoop.mapred.TaskID(m.group(1),
Integer.parseInt(m.group(2)),
CharTaskTypeMaps.getTaskType(m.group(3).charAt(0)),
Integer.parseInt(m.group(4)));
}
String exceptionMsg = "TaskId string : " + str + " is not properly formed" +
"\nReason: " + m.toString();
throw new IllegalArgumentException(exceptionMsg);
}
/**
* Gets the character representing the {@link TaskType}.
*
* @param type the TaskType
* @return the character
*/
public static char getRepresentingCharacter(TaskType type) {
return CharTaskTypeMaps.getRepresentingCharacter(type);
}
/**
* Gets the {@link TaskType} corresponding to the character.
*
* @param c the character
* @return the TaskType
*/
public static TaskType getTaskType(char c) {
return CharTaskTypeMaps.getTaskType(c);
}
/**
* Returns a string of characters describing all possible {@link TaskType}
* values
*
* @return a string of all task type characters
*/
public static String getAllTaskTypes() {
return CharTaskTypeMaps.allTaskTypes;
}
/**
* Maintains the mapping from the character representation of a task type to
* the enum class TaskType constants
*/
static class CharTaskTypeMaps {
private static EnumMap<TaskType, Character> typeToCharMap =
new EnumMap<TaskType,Character>(TaskType.class);
private static Map<Character, TaskType> charToTypeMap =
new HashMap<Character, TaskType>();
static String allTaskTypes = "(m|r|s|c|t)";
static {
setupTaskTypeToCharMapping();
setupCharToTaskTypeMapping();
}
private static void setupTaskTypeToCharMapping() {
typeToCharMap.put(TaskType.MAP, 'm');
typeToCharMap.put(TaskType.REDUCE, 'r');
typeToCharMap.put(TaskType.JOB_SETUP, 's');
typeToCharMap.put(TaskType.JOB_CLEANUP, 'c');
typeToCharMap.put(TaskType.TASK_CLEANUP, 't');
}
private static void setupCharToTaskTypeMapping() {
charToTypeMap.put('m', TaskType.MAP);
charToTypeMap.put('r', TaskType.REDUCE);
charToTypeMap.put('s', TaskType.JOB_SETUP);
charToTypeMap.put('c', TaskType.JOB_CLEANUP);
charToTypeMap.put('t', TaskType.TASK_CLEANUP);
}
static char getRepresentingCharacter(TaskType type) {
return typeToCharMap.get(type);
}
static TaskType getTaskType(char c) {
return charToTypeMap.get(c);
}
}
}