org.sapia.ubik.rmi.server.gc

Class ServerGC

java.lang.Object

org.sapia.ubik.rmi.server.gc.ServerGC

All Implemented Interfaces:

Module, ServerGCMBean, Task

public class ServerGC
extends Object
implements Module, Task, ServerGCMBean

This class implements the server-side distributed garbage collection algorithm.

Author:

Yanick Duchesne

Field Summary

Fields

Modifier and Type	Field and Description
static long	GC_INTERVAL
static long	GC_TIMEOUT

Constructor Summary

Constructors

Constructor and Description
ServerGC()

Method Summary

Methods

Modifier and Type	Method and Description
void	clear()
boolean	containsClient(VmId id) Returns true if this instance contains the passed in VmId.
void	dereference(VmId id, OID oid) Dereferences a given object identifier.
void	exec(TaskContext ctx)
int	getClientCount()
long	getInterval()
int	getRefCount(VmId id, OID oid) Returns the total number of references held on the given object identifier.
int	getSpecificCount(VmId id, OID oid) Returns the total number of references held on the given object by the client whose host corresponds to the passed in VmId.
long	getTimeout()
void	init(ModuleContext context) Called upon Ubik startup.
void	reference(VmId id, OID oid) Increments the reference count of the given object identifier, for the client whose VmId is given.
void	registerRef(VmId id, OID oid, Object o) Registers a given object internally so that it is not garbage collected before clients themselves garbage collect it.
void	setTimeout(long timeout)
void	start(ModuleContext context) Called after #init(), when all modules have initialized.
void	stop() Called upon Ubik shutdown.
void	touch(VmId id) Touches the client info of the VmId passed in.

Methods inherited from class java.lang.Object

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

Field Detail

GC_TIMEOUT

public static final long GC_TIMEOUT

See Also:

Constant Field Values

GC_INTERVAL

public static final long GC_INTERVAL

See Also:

Constant Field Values

Constructor Detail

ServerGC

public ServerGC()

Method Detail

init

public void init(ModuleContext context)

Description copied from interface: Module

Called upon Ubik startup. This method is called only once in this instance's lifetime.

Specified by:

init in interface Module

start

public void start(ModuleContext context)

Description copied from interface: Module

Called after #init(), when all modules have initialized.

Specified by:

start in interface Module

stop

public void stop()

Description copied from interface: Module

Called upon Ubik shutdown.

Specified by:

stop in interface Module

getRefCount

public int getRefCount(VmId id,
              OID oid)

Returns the total number of references held on the given object identifier.

Parameters:

id - a VmId.

oid - an DefaultOID.

Returns:

a reference count, as an int.

getSpecificCount

public int getSpecificCount(VmId id,
                   OID oid)

Returns the total number of references held on the given object by the client whose host corresponds to the passed in VmId.

Parameters:

id - a VmId

oid - an DefaultOID

containsClient

public boolean containsClient(VmId id)

Returns true if this instance contains the passed in VmId.

Returns:

true if this instance contains the passed in VmId.

reference

public void reference(VmId id,
             OID oid)

Increments the reference count of the given object identifier, for the client whose VmId is given.

Parameters:

id - the client's VmId.

oid - the OID of the object whose reference count should be incremented.

registerRef

public void registerRef(VmId id,
               OID oid,
               Object o)

Registers a given object internally so that it is not garbage collected before clients themselves garbage collect it.

Parameters:

id - the VmId of the client to whom a stub corresponding to the passed in object is returned (this in fact creates a remote reference on the object).

oid - the OID that identifies the passed in object locally.

o - the Object for which a stub is eventually returned to the client.

dereference

public void dereference(VmId id,
               OID oid)

Dereferences a given object identifier.

Parameters:

id - the VmId of the client from which the dereferencing call comes.

oid - the DefaultOID to dereference.

touch

public void touch(VmId id)

Touches the client info of the VmId passed in.

Parameters:

id - a VmId

exec

public void exec(TaskContext ctx)

Specified by:

exec in interface Task

Parameters:

ctx - this instance's TaskContext

clear

public void clear()

getInterval

public long getInterval()

Specified by:

getInterval in interface ServerGCMBean

See Also:

Consts.SERVER_GC_INTERVAL

getTimeout

public long getTimeout()

Specified by:

getTimeout in interface ServerGCMBean

See Also:

Consts.SERVER_GC_TIMEOUT

setTimeout

public void setTimeout(long timeout)

Specified by:

setTimeout in interface ServerGCMBean

getClientCount

public int getClientCount()

Specified by:

getClientCount in interface ServerGCMBean

Returns:

the number of clients that the server GC keeps track of.