org.apache.hadoop.hbase

Class ChoreService

java.lang.Object

org.apache.hadoop.hbase.ChoreService

All Implemented Interfaces:

ScheduledChore.ChoreServicer

@InterfaceAudience.Public
public class ChoreService
extends Object
implements ScheduledChore.ChoreServicer

ChoreService is a service that can be used to schedule instances of ScheduledChore to run periodically while sharing threads. The ChoreService is backed by a ScheduledThreadPoolExecutor whose core pool size changes dynamically depending on the number of ScheduledChore scheduled. All of the threads in the core thread pool of the underlying ScheduledThreadPoolExecutor are set to be daemon threads.

The ChoreService provides the ability to schedule, cancel, and trigger instances of ScheduledChore. The ChoreService also provides the ability to check on the status of scheduled chores. The number of threads used by the ChoreService changes based on the scheduling load and whether or not the scheduled chores are executing on time. As more chores are scheduled, there may be a need to increase the number of threads if it is noticed that chores are no longer meeting their scheduled start times. On the other hand, as chores are cancelled, an attempt is made to reduce the number of running threads to see if chores can still meet their start times with a smaller thread pool.

When finished with a ChoreService it is good practice to call shutdown(). Calling this method ensures that all scheduled chores are cancelled and cleaned up properly.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) static class	ChoreService.ChoreServiceThreadFactory Custom ThreadFactory used with the ScheduledThreadPoolExecutor so that all the threads are daemon threads, and thus, don't prevent the JVM from shutting down

Field Summary

Fields

Modifier and Type	Field and Description
private HashMap<ScheduledChore,Boolean>	choresMissingStartTime Maps chores to Booleans which indicate whether or not a chore has caused an increase in the core pool size of the ScheduledThreadPoolExecutor.
private String	coreThreadPoolPrefix The coreThreadPoolPrefix is the prefix that will be applied to all threads within the ScheduledThreadPoolExecutor.
private static org.slf4j.Logger	LOG
static int	MIN_CORE_POOL_SIZE The minimum number of threads in the core pool of the underlying ScheduledThreadPoolExecutor
private HashMap<ScheduledChore,ScheduledFuture<?>>	scheduledChores Maps chores to their futures.
private ScheduledThreadPoolExecutor	scheduler This thread pool is used to schedule all of the Chores

Constructor Summary

Constructors

Constructor and Description
ChoreService(String coreThreadPoolPrefix)
ChoreService(String coreThreadPoolPrefix, boolean jitter)
ChoreService(String coreThreadPoolPrefix, int corePoolSize, boolean jitter)

Method Summary

Modifier and Type	Method and Description
private void	cancelAllChores(boolean mayInterruptIfRunning)
void	cancelChore(ScheduledChore chore) Cancel any ongoing schedules that this chore has with the implementer of this interface.
void	cancelChore(ScheduledChore chore, boolean mayInterruptIfRunning)
(package private) int	getCorePoolSize()
(package private) int	getNumberOfChoresMissingStartTime()
(package private) int	getNumberOfScheduledChores()
boolean	isChoreScheduled(ScheduledChore chore)
boolean	isShutdown()
boolean	isTerminated()
void	onChoreMissedStartTime(ScheduledChore chore) A callback that tells the implementer of this interface that one of the scheduled chores is missing its start time.
private void	printChoreDetails(String header, ScheduledChore chore) Prints a summary of important details about the chore.
private void	printChoreServiceDetails(String header) Prints a summary of important details about the service.
private void	requestCorePoolDecrease() Represents a request to decrease the number of core pool threads.
private boolean	requestCorePoolIncrease() Represents a request to increase the number of core pool threads.
private void	rescheduleChore(ScheduledChore chore)
boolean	scheduleChore(ScheduledChore chore)
void	shutdown() shutdown the service.
boolean	triggerNow(ScheduledChore chore) This method tries to execute the chore immediately.

Methods inherited from class java.lang.Object

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

Field Detail

LOG

private static final org.slf4j.Logger LOG

MIN_CORE_POOL_SIZE

@InterfaceAudience.Private
public static final int MIN_CORE_POOL_SIZE

The minimum number of threads in the core pool of the underlying ScheduledThreadPoolExecutor

See Also:

Constant Field Values

scheduler

private final ScheduledThreadPoolExecutor scheduler

This thread pool is used to schedule all of the Chores

scheduledChores

private final HashMap<ScheduledChore,ScheduledFuture<?>> scheduledChores

Maps chores to their futures. Futures are used to control a chore's schedule

choresMissingStartTime

private final HashMap<ScheduledChore,Boolean> choresMissingStartTime

Maps chores to Booleans which indicate whether or not a chore has caused an increase in the core pool size of the ScheduledThreadPoolExecutor. Each chore should only be allowed to increase the core pool size by 1 (otherwise a single long running chore whose execution is longer than its period would be able to spawn too many threads).

coreThreadPoolPrefix

private final String coreThreadPoolPrefix

The coreThreadPoolPrefix is the prefix that will be applied to all threads within the ScheduledThreadPoolExecutor. The prefix is typically related to the Server that the service is running on. The prefix is useful because it allows us to monitor how the thread pool of a particular service changes over time VIA thread dumps.

Constructor Detail

ChoreService

@InterfaceAudience.Private
public ChoreService(String coreThreadPoolPrefix)

Parameters:

coreThreadPoolPrefix - Prefix that will be applied to the Thread name of all threads spawned by this service

ChoreService

public ChoreService(String coreThreadPoolPrefix,
                    boolean jitter)

Parameters:

coreThreadPoolPrefix - Prefix that will be applied to the Thread name of all threads spawned by this service

jitter - Should chore service add some jitter for all of the scheduled chores. When set to true this will add -10% to 10% jitter.

ChoreService

public ChoreService(String coreThreadPoolPrefix,
                    int corePoolSize,
                    boolean jitter)

Parameters:

coreThreadPoolPrefix - Prefix that will be applied to the Thread name of all threads spawned by this service

corePoolSize - The initial size to set the core pool of the ScheduledThreadPoolExecutor to during initialization. The default size is 1, but specifying a larger size may be beneficial if you know that 1 thread will not be enough.

jitter - Should chore service add some jitter for all of the scheduled chores. When set to true this will add -10% to 10% jitter.

Method Detail

scheduleChore

public boolean scheduleChore(ScheduledChore chore)

Parameters:

chore - Chore to be scheduled. If the chore is already scheduled with another ChoreService instance, that schedule will be cancelled (i.e. a Chore can only ever be scheduled with a single ChoreService instance).

Returns:

true when the chore was successfully scheduled. false when the scheduling failed (typically occurs when a chore is scheduled during shutdown of service)

rescheduleChore

private void rescheduleChore(ScheduledChore chore)

Parameters:

chore - The Chore to be rescheduled. If the chore is not scheduled with this ChoreService yet then this call is equivalent to a call to scheduleChore.

cancelChore

@InterfaceAudience.Private
public void cancelChore(ScheduledChore chore)

Description copied from interface: ScheduledChore.ChoreServicer

Cancel any ongoing schedules that this chore has with the implementer of this interface.

Specified by:

cancelChore in interface ScheduledChore.ChoreServicer

cancelChore

@InterfaceAudience.Private
public void cancelChore(ScheduledChore chore,
                                                   boolean mayInterruptIfRunning)

Specified by:

cancelChore in interface ScheduledChore.ChoreServicer

isChoreScheduled

@InterfaceAudience.Private
public boolean isChoreScheduled(ScheduledChore chore)

Specified by:

isChoreScheduled in interface ScheduledChore.ChoreServicer

Returns:

true when the chore is scheduled with the implementer of this interface

triggerNow

@InterfaceAudience.Private
public boolean triggerNow(ScheduledChore chore)

Description copied from interface: ScheduledChore.ChoreServicer

This method tries to execute the chore immediately. If the chore is executing at the time of this call, the chore will begin another execution as soon as the current execution finishes

If the chore is not scheduled with a ChoreService, this call will fail.

Specified by:

triggerNow in interface ScheduledChore.ChoreServicer

Returns:

false when the chore could not be triggered immediately

getNumberOfScheduledChores

int getNumberOfScheduledChores()

Returns:

number of chores that this service currently has scheduled

getNumberOfChoresMissingStartTime

int getNumberOfChoresMissingStartTime()

Returns:

number of chores that this service currently has scheduled that are missing their scheduled start time

getCorePoolSize

int getCorePoolSize()

Returns:

number of threads in the core pool of the underlying ScheduledThreadPoolExecutor

requestCorePoolIncrease

private boolean requestCorePoolIncrease()

Represents a request to increase the number of core pool threads. Typically a request originates from the fact that the current core pool size is not sufficient to service all of the currently running Chores

Returns:

true when the request to increase the core pool size succeeds

requestCorePoolDecrease

private void requestCorePoolDecrease()

Represents a request to decrease the number of core pool threads. Typically a request originates from the fact that the current core pool size is more than sufficient to service the running Chores.

onChoreMissedStartTime

@InterfaceAudience.Private
public void onChoreMissedStartTime(ScheduledChore chore)

Description copied from interface: ScheduledChore.ChoreServicer

A callback that tells the implementer of this interface that one of the scheduled chores is missing its start time. The implication of a chore missing its start time is that the service's current means of scheduling may not be sufficient to handle the number of ongoing chores (the other explanation is that the chore's execution time is greater than its scheduled period). The service should try to increase its concurrency when this callback is received.

Specified by:

onChoreMissedStartTime in interface ScheduledChore.ChoreServicer

Parameters:

chore - The chore that missed its start time

shutdown

public void shutdown()

shutdown the service. Any chores that are scheduled for execution will be cancelled. Any chores in the middle of execution will be interrupted and shutdown. This service will be unusable after this method has been called (i.e. future scheduling attempts will fail).

isShutdown

public boolean isShutdown()

Returns:

true when the service is shutdown and thus cannot be used anymore

isTerminated

public boolean isTerminated()

Returns:

true when the service is shutdown and all threads have terminated

cancelAllChores

private void cancelAllChores(boolean mayInterruptIfRunning)

printChoreDetails

private void printChoreDetails(String header,
                               ScheduledChore chore)

Prints a summary of important details about the chore. Used for debugging purposes

printChoreServiceDetails

private void printChoreServiceDetails(String header)

Prints a summary of important details about the service. Used for debugging purposes