org.apache.hadoop.hbase

Class ChoreService

java.lang.Object

org.apache.hadoop.hbase.ChoreService

@InterfaceAudience.Private
public class ChoreService
extends Object

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.

Field Summary

Fields

Modifier and Type	Field and Description
static String	CHORE_SERVICE_INITIAL_POOL_SIZE The initial number of threads in the core pool for the ChoreService.
static int	DEFAULT_CHORE_SERVICE_INITIAL_POOL_SIZE
static int	MIN_CORE_POOL_SIZE The minimum number of threads in the core pool of the underlying ScheduledThreadPoolExecutor

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
boolean	isChoreScheduled(ScheduledChore chore) Returns true when the chore is scheduled with the implementer of this interface
boolean	isShutdown() Returns true when the service is shutdown and thus cannot be used anymore
boolean	isTerminated() Returns true when the service is shutdown and all threads have terminated
boolean	scheduleChore(ScheduledChore chore) Schedule a chore.
void	shutdown() Shut down the service.

Methods inherited from class java.lang.Object

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

Field Detail

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

CHORE_SERVICE_INITIAL_POOL_SIZE

public static final String CHORE_SERVICE_INITIAL_POOL_SIZE

The initial number of threads in the core pool for the ChoreService.

See Also:

Constant Field Values

DEFAULT_CHORE_SERVICE_INITIAL_POOL_SIZE

public static final int DEFAULT_CHORE_SERVICE_INITIAL_POOL_SIZE

See Also:

Constant Field Values

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)

Schedule a 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)

isChoreScheduled

@InterfaceAudience.Private
public boolean isChoreScheduled(ScheduledChore chore)

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

shutdown

public void shutdown()

Shut down 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).

Notice that, this will only clean the chore from this ChoreService but you could still schedule the chore with other ChoreService.

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