NAKACK

java.lang.Object
- org.jgroups.stack.Protocol
- - org.jgroups.protocols.pbcast.NAKACK

All Implemented Interfaces:

NakReceiverWindow.Listener, Retransmitter.RetransmitCommand
```
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

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

Constructors
Constructor and Description

NAKACK()

Constructors
Constructor and Description
`NAKACK()`

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`down(Event evt)` Callback.
`java.util.Map`	`dumpStats()`
`int`	`getGcLag()`
`int`	`getMaxXmitBufSize()`
`long`	`getMaxXmitSize()`
`long`	`getMissingMessagesReceived()`
`java.lang.String`	`getName()`
`int`	`getPendingRetransmissionRequests()`
`int`	`getReceivedTableSize()`
`int`	`getSentTableSize()`
`long`	`getXmitRequestsReceived()`
`long`	`getXmitRequestsSent()`
`long`	`getXmitResponsesReceived()`
`long`	`getXmitResponsesSent()`
`void`	`init()` Called after instance has been created (null constructor) and before protocol is started.
`boolean`	`isDiscardDeliveredMsgs()`
`boolean`	`isUseMcastXmit()`
`boolean`	`isXmitFromRandomMember()`
`void`	`missingMessageReceived(long seqno, Message msg)`
`java.lang.String`	`printMessages()`
`java.lang.String`	`printSentMsgs()`
`java.lang.String`	`printStats()`
`java.util.Vector`	`providedDownServices()` List of events that are provided to layers below (they will be handled when sent down from below).
`java.util.Vector`	`providedUpServices()` List of events that are provided to layers above (they will be handled when sent down from above).
`void`	`resetStats()`
`void`	`retransmit(long first_seqno, long last_seqno, Address sender)` Implementation of Retransmitter.RetransmitCommand.
`void`	`setDiscardDeliveredMsgs(boolean discard_delivered_msgs)`
`void`	`setGcLag(int gc_lag)`
`void`	`setMaxXmitBufSize(int max_xmit_buf_size)`
`void`	`setMaxXmitSize(long max_xmit_size)`
`boolean`	`setProperties(java.util.Properties props)` Configures the protocol initially.
`void`	`setUseMcastXmit(boolean use_mcast_xmit)`
`void`	`setXmitFromRandomMember(boolean xmit_from_random_member)`
`void`	`start()` This method is called on a `Channel.connect(String)`.
`void`	`stop()` This method is called on a `Channel.disconnect()`.
`void`	`up(Event evt)` Callback.

Methods inherited from class org.jgroups.stack.Protocol
destroy, downThreadEnabled, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, passDown, passUp, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, 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
  - NAKACK
```
public NAKACK()
```
- Method Detail
  - getName
```
public java.lang.String getName()
```
    Specified by:
    
    getName in class Protocol
  - getXmitRequestsReceived
```
public long getXmitRequestsReceived()
```
  - getXmitRequestsSent
```
public long getXmitRequestsSent()
```
  - getXmitResponsesReceived
```
public long getXmitResponsesReceived()
```
  - getXmitResponsesSent
```
public long getXmitResponsesSent()
```
  - getMissingMessagesReceived
```
public long getMissingMessagesReceived()
```
  - getPendingRetransmissionRequests
```
public int getPendingRetransmissionRequests()
```
  - getSentTableSize
```
public int getSentTableSize()
```
  - getReceivedTableSize
```
public int getReceivedTableSize()
```
  - resetStats
```
public void resetStats()
```
    Overrides:
    
    resetStats in class Protocol
  - init
```
public void init()
          throws java.lang.Exception
```
    Description copied from class: Protocol
    
    Called after instance has been created (null constructor) and before protocol is started. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.
    
    Overrides:
    
    init in class Protocol
    
    Throws:
    
    java.lang.Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception
  - getGcLag
```
public int getGcLag()
```
  - setGcLag
```
public void setGcLag(int gc_lag)
```
  - isUseMcastXmit
```
public boolean isUseMcastXmit()
```
  - setUseMcastXmit
```
public void setUseMcastXmit(boolean use_mcast_xmit)
```
  - isXmitFromRandomMember
```
public boolean isXmitFromRandomMember()
```
  - setXmitFromRandomMember
```
public void setXmitFromRandomMember(boolean xmit_from_random_member)
```
  - isDiscardDeliveredMsgs
```
public boolean isDiscardDeliveredMsgs()
```
  - setDiscardDeliveredMsgs
```
public void setDiscardDeliveredMsgs(boolean discard_delivered_msgs)
```
  - getMaxXmitBufSize
```
public int getMaxXmitBufSize()
```
  - setMaxXmitBufSize
```
public void setMaxXmitBufSize(int max_xmit_buf_size)
```
  - getMaxXmitSize
```
public long getMaxXmitSize()
```
  - setMaxXmitSize
```
public void setMaxXmitSize(long max_xmit_size)
```
  - setProperties
```
public boolean setProperties(java.util.Properties props)
```
    Description copied from class: Protocol
    Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:
```
 "loopback=false;unicast_inport=4444"
 
```
    Overrides:
    
    setProperties in class Protocol
  - dumpStats
```
public java.util.Map dumpStats()
```
    Overrides:
    
    dumpStats in class Protocol
  - printStats
```
public java.lang.String printStats()
```
    Overrides:
    
    printStats in class Protocol
  - providedUpServices
```
public java.util.Vector providedUpServices()
```
    Description copied from class: Protocol
    
    List of events that are provided to layers above (they will be handled when sent down from above).
    
    Overrides:
    
    providedUpServices in class Protocol
    
    Returns:
    Vector (of Integers)
  - providedDownServices
```
public java.util.Vector providedDownServices()
```
    Description copied from class: Protocol
    
    List of events that are provided to layers below (they will be handled when sent down from below).
    
    Overrides:
    
    providedDownServices in class Protocol
    
    Returns:
    Vector (of Integers)
  - start
```
public void start()
           throws java.lang.Exception
```
    Description copied from class: Protocol
    
    This method is called on a Channel.connect(String). Starts work. Protocols are connected and queues are ready to receive events. Will be called from bottom to top. This call will replace the START and START_OK events.
    
    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()
```
    Description copied from class: Protocol
    
    This method is called on a Channel.disconnect(). Stops work (e.g. by closing multicast socket). Will be called from top to bottom. This means that at the time of the method invocation the neighbor protocol below is still working. This method will replace the STOP, STOP_OK, CLEANUP and CLEANUP_OK events. The ProtocolStack guarantees that when this method is called all messages in the down queue will have been flushed
    
    Overrides:
    
    stop in class Protocol
  - 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 !
    
    Overrides:
    
    down in class Protocol
  - 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 !
    
    Overrides:
    
    up in class Protocol
  - retransmit
```
public void retransmit(long first_seqno,
              long last_seqno,
              Address sender)
```
    Implementation of Retransmitter.RetransmitCommand. Called by retransmission thread when gap is detected.
    
    Specified by:
    
    retransmit in interface Retransmitter.RetransmitCommand
    
    Parameters:
    first_seqno - The sequence number of the first missing message
    last_seqno - The sequence number of the last missing message
    sender - The destination of the member to which the retransmit request will be sent (nak-based scheme), or to which the message will be retransmitted (ack-based scheme).
  - missingMessageReceived
```
public void missingMessageReceived(long seqno,
                          Message msg)
```
    Specified by:
    
    missingMessageReceived in interface NakReceiverWindow.Listener
  - printMessages
```
public java.lang.String printMessages()
```
  - printSentMsgs
```
public java.lang.String printSentMsgs()
```

Class NAKACK

Field Summary

Fields inherited from class org.jgroups.stack.Protocol

Constructor Summary

Method Summary

Methods inherited from class org.jgroups.stack.Protocol

Methods inherited from class java.lang.Object

Constructor Detail

NAKACK

Method Detail

getName

getXmitRequestsReceived

getXmitRequestsSent

getXmitResponsesReceived

getXmitResponsesSent

getMissingMessagesReceived

getPendingRetransmissionRequests

getSentTableSize

getReceivedTableSize

resetStats

init

getGcLag

setGcLag

isUseMcastXmit

setUseMcastXmit

isXmitFromRandomMember

setXmitFromRandomMember

isDiscardDeliveredMsgs

setDiscardDeliveredMsgs

getMaxXmitBufSize

setMaxXmitBufSize

getMaxXmitSize

setMaxXmitSize

setProperties

dumpStats

printStats

providedUpServices

providedDownServices

start

stop

down

up

retransmit

missingMessageReceived

printMessages

printSentMsgs