org.apache.hadoop.hbase

Class ChoreService

java.lang.Object

org.apache.hadoop.hbase.ChoreService

@InterfaceAudience.Public
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.

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	isShutdown()
boolean	isTerminated()
boolean	scheduleChore(ScheduledChore chore)
void	shutdown() shutdown the service.

Methods inherited from class java.lang.Object

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

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)

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