org.apache.hadoop.mapred
Class JobHistory

java.lang.Object
  org.apache.hadoop.mapred.JobHistory

public class JobHistory
extends Object

Provides methods for writing to and reading from job history. Job History works in an append mode, JobHistory and its inner classes provide methods to log job events. JobHistory is split into multiple files, format of each file is plain text where each line is of the format [type (key=value)*], where type identifies the type of the record. Type maps to UID of one of the inner classes of this class. Job history is maintained in a master index which contains star/stop times of all jobs with a few other job level properties. Apart from this each job's history is maintained in a seperate history file. name of job history files follows the format jobtrackerId_jobid For parsing the job history it supports a listener based interface where each line is parsed and passed to listener. The listener can create an object model of history or look for specific events and discard rest of the history.

Nested Class Summary

static class	JobHistory.HistoryCleaner Delete history files older than one month.
static class	JobHistory.JobInfo Helper class for logging or reading back events related to job start, finish or failure.
static class	JobHistory.Keys Job history files contain key="value" pairs, where keys belong to this enum.
static interface	JobHistory.Listener Callback interface for reading back log events from JobHistory.
static class	JobHistory.MapAttempt Helper class for logging or reading back events related to start, finish or failure of a Map Attempt on a node.
static class	JobHistory.RecordTypes Record types are identifiers for each line of log in history files.
static class	JobHistory.ReduceAttempt Helper class for logging or reading back events related to start, finish or failure of a Map Attempt on a node.
static class	JobHistory.Task Helper class for logging or reading back events related to Task's start, finish or failure.
static class	JobHistory.TaskAttempt Base class for Map and Reduce TaskAttempts.
static class	JobHistory.Values This enum contains some of the values commonly used by history log events.

Field Summary

static String

JOBTRACKER_START_TIME

Constructor Summary

JobHistory()

Method Summary

static boolean	init(JobConf conf, String hostname) Initialize JobHistory files.
static boolean	isDisableHistory() Returns history disable status.
static void	parseHistoryFromFS(String path, JobHistory.Listener l, FileSystem fs) Parses history file and invokes Listener.handle() for each line of history.
static void	setDisableHistory(boolean disableHistory) Enable/disable history logging.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

JOBTRACKER_START_TIME

public static final String JOBTRACKER_START_TIME

Constructor Detail

JobHistory

public JobHistory()

Method Detail

init

public static boolean init(JobConf conf,
                           String hostname)

Initialize JobHistory files.

Parameters:

conf - Jobconf of the job tracker.

hostname - jobtracker's hostname

Returns:

true if intialized properly false otherwise

parseHistoryFromFS

public static void parseHistoryFromFS(String path,
                                      JobHistory.Listener l,
                                      FileSystem fs)
                               throws IOException

Parses history file and invokes Listener.handle() for each line of history. It can be used for looking through history files for specific items without having to keep whole history in memory.

Parameters:

path - path to history file

l - Listener for history events

fs - FileSystem where history file is present

Throws:

IOException

isDisableHistory

public static boolean isDisableHistory()

Returns history disable status. by default history is enabled so this method returns false.

Returns:

true if history logging is disabled, false otherwise.

setDisableHistory

public static void setDisableHistory(boolean disableHistory)

Enable/disable history logging. Default value is false, so history is enabled by default.

Parameters:

disableHistory - true if history should be disabled, false otherwise.