Package es.bsc.dataclay.storagelocation

Class DataClayDiskGC

java.lang.Object

es.bsc.dataclay.storagelocation.DataClayDiskGC

public final class DataClayDiskGC
extends Object

This class is responsible to collect objects in disk.

Field Summary

Fields

Modifier and Type	Field	Description
protected ScheduledExecutorService	threadPool	Pool for tasks.

Constructor Summary

Constructors

Constructor	Description
DataClayDiskGC(StorageLocationService thestorageLocationService, DataServiceRuntime theruntime, ExecutionEnvironmentID theassociatedEE)	Constructor.

Method Summary

Modifier and Type	Method	Description
void	addToQueueReferenceCounting(ExecutionEnvironmentID theEEID, ObjectID theobjectID, byte[] serializedObject, boolean theisGet, boolean dirty)	Add reference counting of an object ("counter of referenced objects FROM the object serialized provided") into queue so DiskGC can process it.
int	getNumReferencesTo(ObjectID objectID)	Return number of references pointing to object.
void	shutDown()	Finish all threads.
void	updateRefs(Map<ObjectID,Integer> updateCounterRefs)	Update counters of references.

Methods inherited from class java.lang.Object

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

Field Detail

threadPool

protected final ScheduledExecutorService threadPool

Pool for tasks.

Constructor Detail

DataClayDiskGC

public DataClayDiskGC(StorageLocationService thestorageLocationService,
                      DataServiceRuntime theruntime,
                      ExecutionEnvironmentID theassociatedEE)

Constructor.

Parameters:

thestorageLocationService - Storage location service.

theruntime - The runtime to use for communications and others.

theassociatedEE - Associated execution environment ID.

Method Detail

addToQueueReferenceCounting

public void addToQueueReferenceCounting(ExecutionEnvironmentID theEEID,
                                        ObjectID theobjectID,
                                        byte[] serializedObject,
                                        boolean theisGet,
                                        boolean dirty)

Add reference counting of an object ("counter of referenced objects FROM the object serialized provided") into queue so DiskGC can process it. Parameter contains all bytes of the object. We extract the bytes representing the reference counting in order to avoid 'retaining' bytes in memory (resource leak). This function is called during a get from DB, an update or a store. We add the bytes representing the reference counting without deserializing it in order to let thread continue work and wait for GC to deserialize and process it.

Parameters:

theEEID - ID of the execution environment ID of the object.

theobjectID - ID of the object

serializedObject - Serialized object.

theisGet - Indicates if reference counting arrived during a GET operation. If False, we understand it is a wRITE (update/store) operation.

dirty - dirty Indicates object has been modified. If false, it means that bytes only contains reference counting information. DESIGN NOTE: in order to be able to find out which references where removed in complex objects (arrays, collections) GlobalGc decreases all pointed references in a Get procedure and increase them again (except removed ones) during update. While in EE, objects have memory references so they cannot be removed neither.

updateRefs

public void updateRefs(Map<ObjectID,Integer> updateCounterRefs)

Update counters of references.

Parameters:

updateCounterRefs - Update counter of references.

shutDown

public void shutDown()

Finish all threads.

getNumReferencesTo

public int getNumReferencesTo(ObjectID objectID)

Return number of references pointing to object.

Parameters:

objectID - ID of object

Returns:

Number of references pointing to object