Package 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 @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:

  • Field Details

  • Constructor Details

    • 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 Details

    • 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 - any other problem for readFields.

    • 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 - any other problem for write.

    • 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