ScheduledChore (Apache HBase 1.2.12 API)

java.lang.Object
- org.apache.hadoop.hbase.ScheduledChore

All Implemented Interfaces:

Runnable

Direct Known Subclasses:

BalancerChore, CatalogJanitor, CleanerChore, ClusterStatusChore, ClusterStatusPublisher, HealthCheckChore, HeapMemoryManager.HeapMemoryTunerChore, HMaster.PeriodicDoMetrics, HRegionServer.CompactionChecker, HRegionServer.MovedRegionsCleaner, HRegionServer.PeriodicMemstoreFlusher, QuotaCache.QuotaRefresherChore, RegionNormalizerChore, ReplicationZKLockCleanerChore, SplitLogManager.TimeoutMonitor, StorefileRefresherChore
```
@InterfaceAudience.Private
public abstract class ScheduledChore
extends Object
implements Runnable
```
ScheduledChore is a task performed on a period in hbase. ScheduledChores become active once scheduled with a ChoreService via ChoreService.scheduleChore(ScheduledChore). The chore is run in a ScheduledThreadPoolExecutor and competes with other ScheduledChores for access to the threads in the core thread pool. If an unhandled exception occurs, the chore cancellation is logged. Implementers should consider whether or not the Chore will be able to execute within the defined period. It is bad practice to define a ScheduledChore whose execution time exceeds its period since it will try to hog one of the threads in the ChoreService's thread pool.
Don't subclass ScheduledChore if the task relies on being woken up for something to do, such as an entry being added to a queue, etc.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

(package private) static interface ScheduledChore.ChoreServicer

Nested Classes
Modifier and Type	Class and Description
`(package private) static interface`	`ScheduledChore.ChoreServicer`

Field Summary

Fields
Modifier and Type	Field and Description
`private ScheduledChore.ChoreServicer`	`choreServicer` Interface to the ChoreService that this ScheduledChore is scheduled with.
`private static long`	`DEFAULT_INITIAL_DELAY`
`private static TimeUnit`	`DEFAULT_TIME_UNIT` Default values for scheduling parameters should they be excluded during construction
`private boolean`	`initialChoreComplete`
`private long`	`initialDelay`
`private static org.apache.commons.logging.Log`	`LOG`
`private String`	`name`
`private int`	`period` Scheduling parameters.
`private Stoppable`	`stopper` A means by which a ScheduledChore can be stopped.
`private long`	`timeOfLastRun` Variables that encapsulate the meaningful state information
`private long`	`timeOfThisRun`
`private TimeUnit`	`timeUnit`

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`ScheduledChore()` This constructor is for test only.
	`ScheduledChore(String name, Stoppable stopper, int period)`
	`ScheduledChore(String name, Stoppable stopper, int period, long initialDelay)`
	`ScheduledChore(String name, Stoppable stopper, int period, long initialDelay, TimeUnit unit)`

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`cancel()`
`void`	`cancel(boolean mayInterruptIfRunning)`
`protected abstract void`	`chore()` The task to execute on each scheduled execution of the Chore
`void`	`choreForTesting()`
`protected void`	`cleanup()` Override to run cleanup tasks when the Chore encounters an error and must stop running
`(package private) ScheduledChore.ChoreServicer`	`getChoreServicer()`
`long`	`getInitialDelay()`
`private double`	`getMaximumAllowedTimeBetweenRuns()`
`String`	`getName()`
`int`	`getPeriod()`
`Stoppable`	`getStopper()`
`(package private) long`	`getTimeBetweenRuns()`
`(package private) long`	`getTimeOfLastRun()`
`(package private) long`	`getTimeOfThisRun()`
`TimeUnit`	`getTimeUnit()`
`protected boolean`	`initialChore()` Override to run a task before we start looping.
`boolean`	`isInitialChoreComplete()`
`boolean`	`isScheduled()`
`private boolean`	`isValidTime(long time)`
`private boolean`	`missedStartTime()`
`private void`	`onChoreMissedStartTime()` Notify the ChoreService that this chore has missed its start time.
`void`	`run()`
`(package private) void`	`setChoreServicer(ScheduledChore.ChoreServicer service)`
`String`	`toString()`
`boolean`	`triggerNow()`
`private void`	`updateTimeTrackingBeforeRun()` Update our time tracking members.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - LOG
```
private static final org.apache.commons.logging.Log LOG
```
  - name
```
private final String name
```
  - DEFAULT_TIME_UNIT
```
private static final TimeUnit DEFAULT_TIME_UNIT
```
    Default values for scheduling parameters should they be excluded during construction
  - DEFAULT_INITIAL_DELAY
```
private static final long DEFAULT_INITIAL_DELAY
```
    See Also:
    Constant Field Values
  - period
```
private final int period
```
    Scheduling parameters. Used by ChoreService when scheduling the chore to run periodically
  - timeUnit
```
private final TimeUnit timeUnit
```
  - initialDelay
```
private final long initialDelay
```
  - choreServicer
```
private ScheduledChore.ChoreServicer choreServicer
```
    Interface to the ChoreService that this ScheduledChore is scheduled with. null if the chore is not scheduled.
  - timeOfLastRun
```
private long timeOfLastRun
```
    Variables that encapsulate the meaningful state information
  - timeOfThisRun
```
private long timeOfThisRun
```
  - initialChoreComplete
```
private boolean initialChoreComplete
```
  - stopper
```
private final Stoppable stopper
```
    A means by which a ScheduledChore can be stopped. Once a chore recognizes that it has been stopped, it will cancel itself. This is particularly useful in the case where a single stopper instance is given to multiple chores. In such a case, a single Stoppable.stop(String) command can cause many chores to stop together.
- Constructor Detail
  - ScheduledChore
```
protected ScheduledChore()
```
    This constructor is for test only. It allows us to create an object and to call chore() on it.
  - ScheduledChore
```
public ScheduledChore(String name,
              Stoppable stopper,
              int period)
```
    Parameters:
    name - Name assigned to Chore. Useful for identification amongst chores of the same type
    stopper - When Stoppable.isStopped() is true, this chore will cancel and cleanup
    period - Period in millis with which this Chore repeats execution when scheduled.
  - ScheduledChore
```
public ScheduledChore(String name,
              Stoppable stopper,
              int period,
              long initialDelay)
```
    Parameters:
    name - Name assigned to Chore. Useful for identification amongst chores of the same type
    stopper - When Stoppable.isStopped() is true, this chore will cancel and cleanup
    period - Period in millis with which this Chore repeats execution when scheduled.
    initialDelay - Delay before this Chore begins to execute once it has been scheduled. A value of 0 means the chore will begin to execute immediately. Negative delays are invalid and will be corrected to a value of 0.
  - ScheduledChore
```
public ScheduledChore(String name,
              Stoppable stopper,
              int period,
              long initialDelay,
              TimeUnit unit)
```
    Parameters:
    name - Name assigned to Chore. Useful for identification amongst chores of the same type
    stopper - When Stoppable.isStopped() is true, this chore will cancel and cleanup
    period - Period in Timeunit unit with which this Chore repeats execution when scheduled.
    initialDelay - Delay in Timeunit unit before this Chore begins to execute once it has been scheduled. A value of 0 means the chore will begin to execute immediately. Negative delays are invalid and will be corrected to a value of 0.
    unit - The unit that is used to measure period and initialDelay
- Method Detail
  - run
```
public void run()
```
    Specified by:
    
    run in interface Runnable
    
    See Also:
    Thread.run()
  - updateTimeTrackingBeforeRun
```
private void updateTimeTrackingBeforeRun()
```
    Update our time tracking members. Called at the start of an execution of this chore's run() method so that a correct decision can be made as to whether or not we missed the start time
  - onChoreMissedStartTime
```
private void onChoreMissedStartTime()
```
    Notify the ChoreService that this chore has missed its start time. Allows the ChoreService to make the decision as to whether or not it would be worthwhile to increase the number of core pool threads
  - getTimeBetweenRuns
```
long getTimeBetweenRuns()
```
    Returns:
    How long in millis has it been since this chore last run. Useful for checking if the chore has missed its scheduled start time by too large of a margin
  - missedStartTime
```
private boolean missedStartTime()
```
    Returns:
    true when the time between runs exceeds the acceptable threshold
  - getMaximumAllowedTimeBetweenRuns
```
private double getMaximumAllowedTimeBetweenRuns()
```
    Returns:
    max allowed time in millis between runs.
  - isValidTime
```
private boolean isValidTime(long time)
```
    Parameters:
    time - in system millis
    
    Returns:
    true if time is earlier or equal to current milli time
  - triggerNow
```
public boolean triggerNow()
```
    Returns:
    false when the Chore is not currently scheduled with a ChoreService
  - setChoreServicer
```
void setChoreServicer(ScheduledChore.ChoreServicer service)
```
  - cancel
```
public void cancel()
```
  - cancel
```
public void cancel(boolean mayInterruptIfRunning)
```
  - getName
```
public String getName()
```
  - getStopper
```
public Stoppable getStopper()
```
  - getPeriod
```
public int getPeriod()
```
    Returns:
    period to execute chore in getTimeUnit() units
  - getInitialDelay
```
public long getInitialDelay()
```
    Returns:
    initial delay before executing chore in getTimeUnit() units
  - getTimeUnit
```
public TimeUnit getTimeUnit()
```
  - isInitialChoreComplete
```
public boolean isInitialChoreComplete()
```
  - getChoreServicer
```
ScheduledChore.ChoreServicer getChoreServicer()
```
  - getTimeOfLastRun
```
long getTimeOfLastRun()
```
  - getTimeOfThisRun
```
long getTimeOfThisRun()
```
  - isScheduled
```
public boolean isScheduled()
```
    Returns:
    true when this Chore is scheduled with a ChoreService
  - choreForTesting
```
public void choreForTesting()
```
  - chore
```
protected abstract void chore()
```
    The task to execute on each scheduled execution of the Chore
  - initialChore
```
protected boolean initialChore()
```
    Override to run a task before we start looping.
    
    Returns:
    true if initial chore was successful
  - cleanup
```
protected void cleanup()
```
    Override to run cleanup tasks when the Chore encounters an error and must stop running
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class ScheduledChore

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOG

name

DEFAULT_TIME_UNIT

DEFAULT_INITIAL_DELAY

period

timeUnit

initialDelay

choreServicer

timeOfLastRun

timeOfThisRun

initialChoreComplete

stopper

Constructor Detail

ScheduledChore

ScheduledChore

ScheduledChore

ScheduledChore

Method Detail

run

updateTimeTrackingBeforeRun

onChoreMissedStartTime

getTimeBetweenRuns

missedStartTime

getMaximumAllowedTimeBetweenRuns

isValidTime

triggerNow

setChoreServicer

cancel

cancel

getName

getStopper

getPeriod

getInitialDelay

getTimeUnit

isInitialChoreComplete

getChoreServicer

getTimeOfLastRun

getTimeOfThisRun

isScheduled

choreForTesting

chore

initialChore

cleanup

toString