org.apache.hadoop.mapreduce

Class TaskID

java.lang.Object

org.apache.hadoop.mapreduce.ID

org.apache.hadoop.mapred.ID

org.apache.hadoop.mapreduce.TaskID

All Implemented Interfaces:

Comparable<ID>, Writable, WritableComparable<ID>

Direct Known Subclasses:

TaskID

@InterfaceAudience.Public
 @InterfaceStability.Stable
public class TaskID
extends ID

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 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.
An example TaskID is : task_200707121733_0003_m_000005 , which represents the fifth map task in the third job running at the jobtracker started at 200707121733.

Applications should never construct or parse TaskID strings , but rather use appropriate constructors or forName(String) method.

See Also:

JobID, TaskAttemptID

Field Summary

Fields

Modifier and Type	Field and Description
protected static NumberFormat	idFormat
protected static String	TASK
static String	TASK_ID_REGEX
static Pattern	taskIdPattern

Fields inherited from class org.apache.hadoop.mapreduce.ID

id, SEPARATOR

Constructor Summary

Constructors

Constructor and Description
TaskID() Default constructor for Writable.
TaskID(JobID jobId, boolean isMap, int id) Deprecated.
TaskID(JobID jobId, TaskType type, int id) Constructs a TaskID object from given JobID.
TaskID(String jtIdentifier, int jobId, boolean isMap, int id) Deprecated.
TaskID(String jtIdentifier, int jobId, TaskType type, int id) Constructs a TaskInProgressId object from given parts.

Method Summary

Modifier and Type	Method and Description
protected StringBuilder	appendTo(StringBuilder builder) Add the unique string to the given builder.
int	compareTo(ID o) Compare TaskInProgressIds by first jobIds, then by tip numbers.
boolean	equals(Object o)
static TaskID	forName(String str) Construct a TaskID object from given string.
static String	getAllTaskTypes() Returns a string of characters describing all possible TaskType values
JobID	getJobID() Returns the JobID object that this tip belongs to.
static char	getRepresentingCharacter(TaskType type) Gets the character representing the TaskType.
TaskType	getTaskType() Get the type of the task.
static TaskType	getTaskType(char c) Gets the TaskType corresponding to the character.
int	hashCode()
boolean	isMap() Deprecated.
void	readFields(DataInput in) Deserialize the fields of this object from in.
String	toString()
void	write(DataOutput out) Serialize the fields of this object to out.

Methods inherited from class org.apache.hadoop.mapreduce.ID

getId

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

TASK

protected static final String TASK

See Also:

Constant Field Values

idFormat

protected static final NumberFormat idFormat

TASK_ID_REGEX

public static final String TASK_ID_REGEX

taskIdPattern

public static final Pattern taskIdPattern

Constructor Detail

TaskID

public TaskID(JobID jobId,
              TaskType type,
              int id)

Constructs a TaskID object from given JobID.

Parameters:

jobId - JobID that this tip belongs to

type - the TaskType of the task

id - the tip number

TaskID

public TaskID(String jtIdentifier,
              int jobId,
              TaskType type,
              int id)

Constructs a TaskInProgressId object from given parts.

Parameters:

jtIdentifier - jobTracker identifier

jobId - job number

type - the TaskType

id - the tip number

TaskID

@Deprecated
public TaskID(JobID jobId,
                          boolean isMap,
                          int id)

Deprecated.

Constructs a TaskID object from given JobID.

Parameters:

jobId - JobID that this tip belongs to

isMap - whether the tip is a map

id - the tip number

TaskID

@Deprecated
public TaskID(String jtIdentifier,
                          int jobId,
                          boolean isMap,
                          int id)

Deprecated.

Constructs a TaskInProgressId object from given parts.

Parameters:

jtIdentifier - jobTracker identifier

jobId - job number

isMap - whether the tip is a map

id - the tip number

TaskID

public TaskID()

Default constructor for Writable. Sets the task type to TaskType.REDUCE, the ID to 0, and the job ID to an empty job ID.

Method Detail

getJobID

public JobID getJobID()

Returns the JobID object that this tip belongs to.

Returns:

the JobID object

isMap

@Deprecated
public boolean isMap()

Deprecated.

Returns whether this TaskID is a map ID.

Returns:

whether this TaskID is a map ID

getTaskType

public TaskType getTaskType()

Get the type of the task.

Returns:

the type of the task

equals

public boolean equals(Object o)

Overrides:

equals in class ID

compareTo

public int compareTo(ID o)

Compare TaskInProgressIds by first jobIds, then by tip numbers. Reducers are defined as greater than mappers.

Specified by:

compareTo in interface Comparable<ID>

Overrides:

compareTo in class ID

Parameters:

o - the TaskID against which to compare

Returns:

0 if equal, positive if this TaskID is greater, and negative if this TaskID is less

toString

public String toString()

Overrides:

toString in class ID

appendTo

protected StringBuilder appendTo(StringBuilder builder)

Add the unique string to the given builder.

Parameters:

builder - the builder to append to

Returns:

the builder that was passed in

hashCode

public int hashCode()

Overrides:

hashCode in class ID

readFields

public void readFields(DataInput in)
                throws IOException

Description copied from interface: Writable

Deserialize the fields of this object from in.

For efficiency, implementations should attempt to re-use storage in the existing object where possible.

Specified by:

readFields in interface Writable

Overrides:

readFields in class ID

Parameters:

in - DataInput to deseriablize this object from.

Throws:

IOException

write

public void write(DataOutput out)
           throws IOException

Description copied from interface: Writable

Serialize the fields of this object to out.

Specified by:

write in interface Writable

Overrides:

write in class ID

Parameters:

out - DataOuput to serialize this object into.

Throws:

IOException

forName

public static TaskID forName(String str)
                      throws IllegalArgumentException

Construct a TaskID object from given string.

Parameters:

str - the target string

Returns:

constructed TaskID object or null if the given String is null

Throws:

IllegalArgumentException - if the given string is malformed

getRepresentingCharacter

public static char getRepresentingCharacter(TaskType type)

Gets the character representing the TaskType.

Parameters:

type - the TaskType

Returns:

the character

getTaskType

public static TaskType getTaskType(char c)

Gets the TaskType corresponding to the character.

Parameters:

c - the character

Returns:

the TaskType

getAllTaskTypes

public static String getAllTaskTypes()

Returns a string of characters describing all possible TaskType values

Returns:

a string of all task type characters