org.apache.hadoop.mapreduce
Class TaskID

java.lang.Object
  extended by org.apache.hadoop.mapreduce.ID
      extended by org.apache.hadoop.mapred.ID
          extended by 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
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)
          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
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()
           
 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
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()
Method Detail

getJobID

public JobID getJobID()
Returns the JobID object that this tip belongs to


isMap

@Deprecated
public boolean isMap()
Deprecated. 

Returns whether this TaskID is a map ID


getTaskType

public TaskType getTaskType()
Get 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. 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

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()


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