org.jgroups.protocols.pbcast

Class NAKACK

public class NAKACK extends Protocol implements Retransmitter.RetransmitCommand, NakReceiverWindow.Listener

Negative AcKnowledgement layer (NAKs). Messages are assigned a monotonically increasing sequence number (seqno). Receivers deliver messages ordered according to seqno and request retransmission of missing messages. Retransmitted messages are bundled into bigger ones, e.g. when getting an xmit request for messages 1-10, instead of sending 10 unicast messages, we bundle all 10 messages into 1 and send it. However, since this protocol typically sits below FRAG, we cannot count on FRAG to fragement/defragment the (possibly) large message into smaller ones. Therefore we only bundle messages up to max_xmit_size bytes to prevent too large messages. For example, if the bundled message size was a total of 34000 bytes, and max_xmit_size=16000, we'd send 3 messages: 2 16K and a 2K message. Note that max_xmit_size should be the same value as FRAG.frag_size (or smaller).
Retransmit requests are always sent to the sender. If the sender dies, and not everyone has received its messages, they will be lost. In the future, this may be changed to have receivers store all messages, so that retransmit requests can be answered by any member. Trivial to implement, but not done yet. For most apps, the default retransmit properties are sufficient, if not use vsync.

Author: Bela Ban

Constructor Summary
NAKACK()
Method Summary
voiddown(Event evt)
Callback.
MapdumpStats()
intgetGcLag()
intgetMaxXmitBufSize()
longgetMaxXmitSize()
longgetMissingMessagesReceived()
StringgetName()
intgetPendingRetransmissionRequests()
intgetReceivedTableSize()
intgetSentTableSize()
longgetXmitRequestsReceived()
longgetXmitRequestsSent()
longgetXmitResponsesReceived()
longgetXmitResponsesSent()
voidinit()
booleanisDiscardDeliveredMsgs()
booleanisUseMcastXmit()
booleanisXmitFromRandomMember()
voidmissingMessageReceived(long seqno, Message msg)
StringprintMessages()
StringprintSentMsgs()
StringprintStats()
VectorprovidedDownServices()
VectorprovidedUpServices()
voidresetStats()
voidretransmit(long first_seqno, long last_seqno, Address sender)
Implementation of Retransmitter.RetransmitCommand.
voidsetDiscardDeliveredMsgs(boolean discard_delivered_msgs)
voidsetGcLag(int gc_lag)
voidsetMaxXmitBufSize(int max_xmit_buf_size)
voidsetMaxXmitSize(long max_xmit_size)
booleansetProperties(Properties props)
voidsetUseMcastXmit(boolean use_mcast_xmit)
voidsetXmitFromRandomMember(boolean xmit_from_random_member)
voidstart()
voidstop()
voidup(Event evt)
Callback.

Constructor Detail

NAKACK

public NAKACK()

Method Detail

down

public void down(Event evt)
Callback. Called by superclass when event may be handled.

Do not use passDown() in this method as the event is passed down by default by the superclass after this method returns !

dumpStats

public Map dumpStats()

getGcLag

public int getGcLag()

getMaxXmitBufSize

public int getMaxXmitBufSize()

getMaxXmitSize

public long getMaxXmitSize()

getMissingMessagesReceived

public long getMissingMessagesReceived()

getName

public String getName()

getPendingRetransmissionRequests

public int getPendingRetransmissionRequests()

getReceivedTableSize

public int getReceivedTableSize()

getSentTableSize

public int getSentTableSize()

getXmitRequestsReceived

public long getXmitRequestsReceived()

getXmitRequestsSent

public long getXmitRequestsSent()

getXmitResponsesReceived

public long getXmitResponsesReceived()

getXmitResponsesSent

public long getXmitResponsesSent()

init

public void init()

isDiscardDeliveredMsgs

public boolean isDiscardDeliveredMsgs()

isUseMcastXmit

public boolean isUseMcastXmit()

isXmitFromRandomMember

public boolean isXmitFromRandomMember()

missingMessageReceived

public void missingMessageReceived(long seqno, Message msg)

printMessages

public String printMessages()

printSentMsgs

public String printSentMsgs()

printStats

public String printStats()

providedDownServices

public Vector providedDownServices()

providedUpServices

public Vector providedUpServices()

resetStats

public void resetStats()

retransmit

public void retransmit(long first_seqno, long last_seqno, Address sender)
Implementation of Retransmitter.RetransmitCommand. Called by retransmission thread when gap is detected.

setDiscardDeliveredMsgs

public void setDiscardDeliveredMsgs(boolean discard_delivered_msgs)

setGcLag

public void setGcLag(int gc_lag)

setMaxXmitBufSize

public void setMaxXmitBufSize(int max_xmit_buf_size)

setMaxXmitSize

public void setMaxXmitSize(long max_xmit_size)

setProperties

public boolean setProperties(Properties props)

setUseMcastXmit

public void setUseMcastXmit(boolean use_mcast_xmit)

setXmitFromRandomMember

public void setXmitFromRandomMember(boolean xmit_from_random_member)

start

public void start()

stop

public void stop()

up

public void up(Event evt)
Callback. Called by superclass when event may be handled.

Do not use PassUp in this method as the event is passed up by default by the superclass after this method returns !

Copyright ? 1998-2005 Bela Ban. All Rights Reserved.