ostore.archive.dissemination
Class DisseminatorStage

java.lang.Object
  |
  +--ostore.archive.dissemination.DisseminatorStage

All Implemented Interfaces:

EventHandlerIF, ProfilableIF, SingleThreadedEventHandlerIF

public class DisseminatorStage

extends Object

implements SingleThreadedEventHandlerIF, EventHandlerIF, ProfilableIF

The DisseminatorStage is the last step of the archival process. The DisseminatorStage completes the archival process by sending all Disseminatables to unique StorageServers.

The DisseminatorStage sends one Disseminatable to each StorageServer in a dissemination set, a set of nodes that fail together with low correlation, and waits for signed (i.e. MAC'd Message Authentication Certificate) acknowledgements. If ACKs are received for all Disseminatables, dissemination is complete. IfACKs for some Disseminatables are not received, the process DisseminatorStage must decide if enough Disseminatables were acknowledged to consider the dissemination complete (i.e. effective). If not, the DisseminatorStage may re-send unacknowledged or NACK'd Disseminatables to the extra members of the dissemination set or redisseminate completely. Note that while the DisseminatorStage normally uses recently-created dissemination sets, it may reuse old, unexpired sets if necessary.

USAGE

To prepare the DisseminatorStage to disseminate Disseminatables, dispatch a BucketsToDisseminateEvent containing the resulting GUID's of all the uniquely modified VerifiableBlocks, the V-GUID (i.e. version GUID), and the A-GUID of the object.

The DisseminatorStage will then verify that it has an unexpired dissemination set associated with the A-GUID. If not, the DisseminatorStage contacts a SetCreator requesting a new dissemination set (i.e. RequestDisseminationSetMsg). When a RequestDisseminationSetResponseMsg is received the DisseminatorStage updates its state associated with the A-GUID.

To actually disseminate, dispatch a DisseminateFragsReq. The DisseminatorStage will then dispatch a DisseminateFragMsg to each member of the dissemination set. The process is done when enough DisseminateFragAckMsg are received to consider the dissemination effective.

Finally, the DissemintorStage will dispatch a DisseminateFragsResp signaling that the Disseminatables have been successfully disseminated.

INITIALIZATION PARAMETERS

node_id

NodeId of the local server where this stage is running.

StorageServer

Willingness for local server to serve as a Storage Server (true or false).

CompareMessages

Flag GenerateFragsStage to store original message to compare to after block has been reconstructed. For debugging only set to true; otherwise, false.

AlarmTimeout

Period to timeout (in milliseconds)

Version:

$Id: DisseminatorStage.java,v 1.37 2004/05/13 20:13:06 hweather Exp $

Author:

Hakim Weatherspoon

See Also:

SetCreatorStage, GenerateFragsStage, GenerateChkptStage, DisseminateFragMsg, DisseminateFragAckMsg, DisseminateFragsReq, DisseminateFragsResp, Disseminatable, Fragment, VerifiableBlock, DataObject, Btree.InteriorNode, DataObject.DataBlock

Constructor Summary

DisseminatorStage()

Method Summary

void	destroy()
void	handleEvent(QueueElementIF item)
void	handleEvents(QueueElementIF[] items)
void	init(ConfigDataIF config)
int	profileSize()

Methods inherited from class java.lang.Object

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

Constructor Detail

DisseminatorStage

public DisseminatorStage()

Method Detail

handleEvent

public void handleEvent(QueueElementIF item)
                 throws EventHandlerException

Specified by:

handleEvent in interface EventHandlerIF

EventHandlerException

handleEvents

public void handleEvents(QueueElementIF[] items)
                  throws EventHandlerException

Specified by:

handleEvents in interface EventHandlerIF

EventHandlerException

init

public void init(ConfigDataIF config)
          throws Exception

Specified by:

init in interface EventHandlerIF

Exception

destroy

public void destroy()
             throws Exception

Specified by:

destroy in interface EventHandlerIF

Exception

profileSize

public int profileSize()

Specified by:

profileSize in interface ProfilableIF