org.apache.hadoop.service

Class CompositeService

java.lang.Object

org.apache.hadoop.service.AbstractService

org.apache.hadoop.service.CompositeService

All Implemented Interfaces:

Closeable, AutoCloseable, Service

@InterfaceAudience.Public
@InterfaceStability.Evolving
public class CompositeService
extends AbstractService

Composition of services.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CompositeService.CompositeServiceShutdownHook JVM Shutdown hook for CompositeService which will stop the give CompositeService gracefully in case of JVM shutdown.

Nested classes/interfaces inherited from interface org.apache.hadoop.service.Service

Service.STATE

Field Summary

Fields

Modifier and Type	Field and Description
protected static boolean	STOP_ONLY_STARTED_SERVICES Policy on shutdown: attempt to close everything (purest) or only try to close started services (which assumes that the service implementations may not handle the stop() operation except when started.

Constructor Summary

Constructors

Constructor and Description
CompositeService(String name)

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	addIfService(Object object) If the passed object is an instance of Service, add it to the list of services managed by this CompositeService
protected void	addService(Service service) Add the passed Service to the list of services managed by this CompositeService
List<Service>	getServices() Get a cloned list of services
protected boolean	removeService(Service service)
protected void	serviceInit(Configuration conf) All initialization code needed by a service.
protected void	serviceStart() Actions called during the INITED to STARTED transition.
protected void	serviceStop() Actions called during the transition to the STOPPED state.

Methods inherited from class org.apache.hadoop.service.AbstractService

close, getBlockers, getConfig, getFailureCause, getFailureState, getLifecycleHistory, getName, getServiceState, getStartTime, init, isInState, noteFailure, putBlocker, registerGlobalListener, registerServiceListener, removeBlocker, setConfig, start, stop, toString, unregisterGlobalListener, unregisterServiceListener, waitForServiceToStop

Methods inherited from class java.lang.Object

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

Field Detail

STOP_ONLY_STARTED_SERVICES

protected static final boolean STOP_ONLY_STARTED_SERVICES

Policy on shutdown: attempt to close everything (purest) or only try to close started services (which assumes that the service implementations may not handle the stop() operation except when started. Irrespective of this policy, if a child service fails during its init() or start() operations, it will have stop() called on it.

See Also:

Constant Field Values

Constructor Detail

CompositeService

public CompositeService(String name)

Method Detail

getServices

public List<Service> getServices()

Get a cloned list of services

Returns:

a list of child services at the time of invocation - added services will not be picked up.

addService

protected void addService(Service service)

Add the passed Service to the list of services managed by this CompositeService

Parameters:

service - the Service to be added

addIfService

protected boolean addIfService(Object object)

If the passed object is an instance of Service, add it to the list of services managed by this CompositeService

Parameters:

object -

Returns:

true if a service is added, false otherwise.

removeService

protected boolean removeService(Service service)

serviceInit

protected void serviceInit(Configuration conf)
                    throws Exception

Description copied from class: AbstractService

All initialization code needed by a service. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in AbstractService.init(Configuration) prevents re-entrancy. The base implementation checks to see if the subclass has created a new configuration instance, and if so, updates the base class value

Overrides:

serviceInit in class AbstractService

Parameters:

conf - configuration

Throws:

Exception - on a failure -these will be caught, possibly wrapped, and wil; trigger a service stop

serviceStart

protected void serviceStart()
                     throws Exception

Description copied from class: AbstractService

Actions called during the INITED to STARTED transition. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in AbstractService.start() prevents re-entrancy.

Overrides:

serviceStart in class AbstractService

Throws:

Exception - if needed -these will be caught, wrapped, and trigger a service stop

serviceStop

protected void serviceStop()
                    throws Exception

Description copied from class: AbstractService

Actions called during the transition to the STOPPED state. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in AbstractService.stop() prevents re-entrancy. Implementations MUST write this to be robust against failures, including checks for null references -and for the first failure to not stop other attempts to shut down parts of the service.

Overrides:

serviceStop in class AbstractService

Throws:

Exception - if needed -these will be caught and logged.