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

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

protected static NumberFormat	idFormat
protected static String	TASK

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

id, SEPARATOR

Constructor Summary

TaskID()

TaskID(JobID jobId, boolean isMap, int id)
Constructs a TaskID object from given JobID.

TaskID(String jtIdentifier, int jobId, boolean isMap, int id)
Constructs a TaskInProgressId object from given parts.

Method Summary

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
JobID	getJobID() Returns the JobID object that this tip belongs to
int	hashCode()
boolean	isMap() Returns whether this TaskID is a map ID
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

Constructor Detail

TaskID

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

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

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

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()

Method Detail

getJobID

public JobID getJobID()

Returns the JobID object that this tip belongs to

isMap

public boolean isMap()

Returns whether this TaskID is a map ID

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. Reduces are defined as greater then maps.

Specified by:

compareTo in interface Comparable<ID>

Overrides:

compareTo in class ID

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

Returns:

constructed TaskID object or null if the given String is null

Throws:

IllegalArgumentException - if the given string is malformed