org.jgroups.protocols
Class TOTAL

java.lang.Object
  org.jgroups.stack.Protocol
      org.jgroups.protocols.TOTAL

public class TOTAL
extends Protocol

Implements the total ordering layer using a message sequencer

The protocol guarantees that all bcast sent messages will be delivered in the same order to all members. For that it uses a sequencer which assignes monotonically increasing sequence ID to broadcasts. Then all group members deliver the bcasts in ascending sequence ID order.

• When a bcast message comes down to this layer, it is placed in the pending down queue. A bcast request is sent to the sequencer.
• When the sequencer receives a bcast request, it creates a bcast reply message and assigns to it a monotonically increasing seqID and sends it back to the source of the bcast request.
• When a broadcast reply is received, the corresponding bcast message is assigned the received seqID. Then it is broadcasted.
• Received bcasts are placed in the up queue. The queue is sorted according to the seqID of the bcast. Any message at the head of the up queue with a seqID equal to the next expected seqID is delivered to the layer above.
• Unicast messages coming from the layer below are forwarded above.
• Unicast messages coming from the layer above are forwarded below.

Please note that once a BLOCK_OK is acknowledged messages coming from above are discarded! Either the application must stop sending messages when a BLOCK event is received from the channel or a QUEUE layer should be placed above this one. Received messages are still delivered above though.

bcast requests are retransmitted periodically until a bcast reply is received. In case a BCAST_REP is on its way during a BCAST_REQ retransmission, then the next BCAST_REP will be to a non-existing BCAST_REQ. So, a null BCAST message is sent to fill the created gap in the seqID of all members.

Author:

i.georgiadis@doc.ic.ac.uk, Bela Ban

Nested Class Summary

static class

TOTAL.Header The header processed by the TOTAL layer and intended for TOTAL inter-stack communication

Field Summary

Fields inherited from class org.jgroups.stack.Protocol

down_handler, down_prot, down_queue, down_thread, down_thread_prio, log, observer, props, stack, stats, up_handler, up_prot, up_queue, up_thread, up_thread_prio

Constructor Summary

TOTAL()
Create the TOTAL layer

Method Summary

void	down(Event event) Process an event coming from the layer above
java.lang.String	getName()
java.util.Vector	requiredDownServices() Events that some layer below must handle
java.util.Vector	requiredUpServices() Events that some layer above must handle
boolean	setProperties(java.util.Properties properties) Configure the protocol based on the given list of properties
void	start() Prepare this layer to receive messages from above
void	stop() Handle the stop() method travelling down the stack.
void	up(Event event) Process an event coming from the layer below

Methods inherited from class org.jgroups.stack.Protocol

destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, resetStats, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, startDownHandler, startUpHandler, statsEnabled, stopInternal, upThreadEnabled

Methods inherited from class java.lang.Object

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

Constructor Detail

TOTAL

public TOTAL()

Create the TOTAL layer

Method Detail

getName

public java.lang.String getName()

Specified by:

getName in class Protocol

Returns:

this protocol's name

setProperties

public boolean setProperties(java.util.Properties properties)

Configure the protocol based on the given list of properties

Overrides:

setProperties in class Protocol

Parameters:

properties - the list of properties to use to setup this layer

Returns:

false if there was any unrecognized property or a property with an invalid value

requiredDownServices

public java.util.Vector requiredDownServices()

Events that some layer below must handle

Overrides:

requiredDownServices in class Protocol

Returns:

the set of Events that must be handled by some layer below

requiredUpServices

public java.util.Vector requiredUpServices()

Events that some layer above must handle

Overrides:

requiredUpServices in class Protocol

Returns:

the set of Events that must be handled by some layer above

start

public void start()
           throws java.lang.Exception

Prepare this layer to receive messages from above

Overrides:

start in class Protocol

Throws:

java.lang.Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception

stop

public void stop()

Handle the stop() method travelling down the stack.

The local addr is set to null, since after a Start->Stop->Start sequence this member's addr is not guaranteed to be the same

Overrides:

stop in class Protocol

up

public void up(Event event)

Process an event coming from the layer below

Overrides:

up in class Protocol

Parameters:

event - the event to process

down

public void down(Event event)

Process an event coming from the layer above

Overrides:

down in class Protocol

Parameters:

event - the event to process