org.apache.hadoop.lib.server

Class BaseService

java.lang.Object

org.apache.hadoop.lib.server.BaseService

All Implemented Interfaces:

Service

Direct Known Subclasses:

FileSystemAccessService, GroupsService, InstrumentationService, SchedulerService

@InterfaceAudience.Private
public abstract class BaseService
extends Object
implements Service

Convenience class implementing the Service interface.

Constructor Summary

Constructors

Constructor and Description
BaseService(String prefix) Service constructor.

Method Summary

Modifier and Type	Method and Description
void	destroy() Destroy the services.
protected String	getPrefix() Returns the service prefix.
protected String	getPrefixedName(String name) Returns the full prefixed name of a service property.
protected Server	getServer() Returns the server owning the service.
protected org.apache.hadoop.conf.Configuration	getServiceConfig() Returns the service configuration properties.
Class[]	getServiceDependencies() Returns the service dependencies of this service.
protected abstract void	init() Initializes the server.
void	init(Server server) Initializes the service.
void	postInit() Post initializes the service.
void	serverStatusChange(Server.Status oldStatus, Server.Status newStatus) Notification callback when the server changes its status.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.hadoop.lib.server.Service

getInterface

Constructor Detail

BaseService

public BaseService(String prefix)

Service constructor.

Parameters:

prefix - service prefix.

Method Detail

init

public final void init(Server server)
                throws ServiceException

Initializes the service.

It collects all service properties (properties having the #SERVER#.#SERVICE#. prefix). The property names are then trimmed from the #SERVER#.#SERVICE#. prefix.

After collecting the service properties it delegates to the init() method.

Specified by:

init in interface Service

Parameters:

server - the server initializing the service, give access to the server context.

Throws:

ServiceException - thrown if the service could not be initialized.

postInit

public void postInit()
              throws ServiceException

Post initializes the service. This method is called by the Server after all services of the server have been initialized.

This method does a NOP.

Specified by:

postInit in interface Service

Throws:

ServiceException - thrown if the service could not be post-initialized.

destroy

public void destroy()

Destroy the services. This method is called once, when the Server owning the service is being destroyed.

This method does a NOP.

Specified by:

destroy in interface Service

getServiceDependencies

public Class[] getServiceDependencies()

Returns the service dependencies of this service. The service will be instantiated only if all the service dependencies are already initialized.

This method returns an empty array (size 0)

Specified by:

getServiceDependencies in interface Service

Returns:

an empty array (size 0).

serverStatusChange

public void serverStatusChange(Server.Status oldStatus,
                               Server.Status newStatus)
                        throws ServiceException

Notification callback when the server changes its status.

This method returns an empty array (size 0)

Specified by:

serverStatusChange in interface Service

Parameters:

oldStatus - old server status.

newStatus - new server status.

Throws:

ServiceException - thrown if the service could not process the status change.

getPrefix

protected String getPrefix()

Returns the service prefix.

Returns:

the service prefix.

getServer

protected Server getServer()

Returns the server owning the service.

Returns:

the server owning the service.

getPrefixedName

protected String getPrefixedName(String name)

Returns the full prefixed name of a service property.

Parameters:

name - of the property.

Returns:

prefixed name of the property.

getServiceConfig

protected org.apache.hadoop.conf.Configuration getServiceConfig()

Returns the service configuration properties. Property names are trimmed off from its prefix.

The sevice configuration properties are all properties with names starting with #SERVER#.#SERVICE#. in the server configuration.

Returns:

the service configuration properties with names trimmed off from their #SERVER#.#SERVICE#. prefix.

init

protected abstract void init()
                      throws ServiceException

Initializes the server.

This method is called by init(Server) after all service properties (properties prefixed with

Throws:

ServiceException - thrown if the service could not be initialized.