TaskID (Hadoop 1.2.1 API)
Date: 2013-07-22

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## org.apache.hadoop.mapred
Class TaskID

    java.lang.Object
      org.apache.hadoop.mapreduce.ID
          org.apache.hadoop.mapred.ID
              org.apache.hadoop.mapreduce.TaskID
                  org.apache.hadoop.mapred.TaskID

All Implemented Interfaces:
  Comparable<ID>, Writable, WritableComparable<ID>

    public class TaskID

extends TaskID

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 inherited from class org.apache.hadoop.mapreduce.TaskID
`idFormat, 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
`static TaskID` | `downgrade(TaskID old)` Downgrade a new TaskID to an old one
`static TaskID` | `forName(String str)`
`JobID` | `getJobID()` Returns the `JobID` object that this tip belongs to
`static String` | `getTaskIDsPattern(String jtIdentifier, Integer jobId, Boolean isMap, Integer taskId)` Deprecated.
`static TaskID` | `read(DataInput in)` Deprecated.

Methods inherited from class org.apache.hadoop.mapreduce.TaskID
`appendTo, compareTo, equals, hashCode, isMap, readFields, toString, write`

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`

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

### downgrade

    public static TaskID downgrade(TaskID old)

  Downgrade a new TaskID to an old one

  Parameters:
    `old` - a new or old TaskID
  Returns:
    either old or a new TaskID build to match old

### read

    @Deprecated
    public static TaskID read(DataInput in)
                       throws IOException

  Deprecated.

  Throws:
    `IOException`

### getJobID

    public JobID getJobID()

  Description copied from class: `TaskID`
  Returns the `JobID` object that this tip belongs to

  Overrides:
    `getJobID` in class `TaskID`

### getTaskIDsPattern

    @Deprecated
    public static String getTaskIDsPattern(String jtIdentifier,
                                                      Integer jobId,
                                                      Boolean isMap,
                                                      Integer taskId)

  Deprecated.

  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 the first map task of any jobtracker, of any job, we would use :

       TaskID.getTaskIDsPattern(null, null, true, 1);

  which will return :

       "task_[^_]*_[0-9]*_m_000001*"

  Parameters:
    `jtIdentifier` - jobTracker identifier, or null
    `jobId` - job number, or null
    `isMap` - whether the tip is a map, or null
    `taskId` - taskId number, or null
  Returns:
    a regex pattern matching TaskIDs

### forName

    public static TaskID forName(String str)
                          throws IllegalArgumentException

  Throws:
    `IllegalArgumentException`

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Copyright © 2009 The Apache Software Foundation