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org.jgroups.protocols
Class FRAG  

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

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public class FRAG

extends org.jgroups.stack.Protocol

Fragmentation layer. Fragments messages larger than FRAG_SIZE into smaller packets. Reassembles fragmented packets into bigger ones. The fragmentation number is prepended to the messages as a header (and removed at the receiving side).

Each fragment is identified by (a) the sender (part of the message to which the header is appended), (b) the fragmentation ID (which is unique per FRAG layer (monotonically increasing) and (c) the fragement ID which ranges from 0 to number_of_fragments-1.

Requirement: lossless delivery (e.g. NAK, ACK). No requirement on ordering. Works for both unicast and multicast messages.

Version:

$Id: FRAG.java,v 1.28 2005/10/28 07:42:41 belaban Exp $

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Nested Class Summary
(package private) static class	FRAG.FragmentationList           A fragmentation list keeps a list of fragmentation tables sorted by an Address ( the sender ).
(package private) static class	FRAG.FragmentationTable           Keeps track of the fragments that are received.

 

Field Summary
private  org.jgroups.util.ExposedByteArrayOutputStream	bos
private  int	curr_id
private  int	frag_size
private  FRAG.FragmentationList	fragment_list
private  java.util.Vector	members
private static java.lang.String	name
(package private)  long	num_received_frags
(package private)  long	num_received_msgs
(package private)  long	num_sent_frags
(package private)  long	num_sent_msgs

 

Fields inherited from class org.jgroups.stack.Protocol

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

 

Constructor Summary

FRAG()

 

Method Summary
void	down(org.jgroups.Event evt)           Fragment a packet if larger than frag_size (add a header).
private  void	fragment(org.jgroups.Message msg)           Send all fragments as separate messages (with same ID !).
int	getFragSize()
java.lang.String	getName()
long	getNumberOfReceivedFragments()
long	getNumberOfReceivedMessages()
long	getNumberOfSentFragments()
long	getNumberOfSentMessages()
(package private)  void	handleConfigEvent(java.util.HashMap map)
void	resetStats()
void	setFragSize(int s)
boolean	setProperties(java.util.Properties props)           Setup the Protocol instance acording to the configuration string
private  void	unfragment(org.jgroups.Message msg)           1.
void	up(org.jgroups.Event evt)           If event is a message, if it is fragmented, re-assemble fragments into big message and pass up the stack.

 

Methods inherited from class org.jgroups.stack.Protocol

destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, isTrace, isWarn, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setTrace, setUpProtocol, setWarn, start, startDownHandler, startUpHandler, statsEnabled, stop, stopInternal, upThreadEnabled

 

Methods inherited from class java.lang.Object

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

 

Field Detail

frag_size

private int frag_size

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fragment_list

private final FRAG.FragmentationList fragment_list

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curr_id

private int curr_id

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bos

private final org.jgroups.util.ExposedByteArrayOutputStream bos

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members

private final java.util.Vector members

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name

private static final java.lang.String name

See Also:

Constant Field Values

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num_sent_msgs

long num_sent_msgs

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num_sent_frags

long num_sent_frags

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num_received_msgs

long num_received_msgs

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num_received_frags

long num_received_frags

Constructor Detail

FRAG

public FRAG()

Method Detail

getName

public java.lang.String getName()

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getFragSize

public int getFragSize()

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setFragSize

public void setFragSize(int s)

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getNumberOfSentMessages

public long getNumberOfSentMessages()

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getNumberOfSentFragments

public long getNumberOfSentFragments()

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getNumberOfReceivedMessages

public long getNumberOfReceivedMessages()

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getNumberOfReceivedFragments

public long getNumberOfReceivedFragments()

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setProperties

public boolean setProperties(java.util.Properties props)

Setup the Protocol instance acording to the configuration string

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resetStats

public void resetStats()

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down

public void down(org.jgroups.Event evt)

Fragment a packet if larger than frag_size (add a header). Otherwise just pass down. Only add a header if framentation is needed !

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up

public void up(org.jgroups.Event evt)

If event is a message, if it is fragmented, re-assemble fragments into big message and pass up the stack.

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fragment

private void fragment(org.jgroups.Message msg)

Send all fragments as separate messages (with same ID !). Example:

 Given the generated ID is 2344, number of fragments=3, message {dst,src,buf}
 would be fragmented into:
 

 [2344,3,0]{dst,src,buf1},
 [2344,3,1]{dst,src,buf2} and
 [2344,3,2]{dst,src,buf3}
 

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unfragment

private void unfragment(org.jgroups.Message msg)

1. Get all the fragment buffers 2. When all are received -> Assemble them into one big buffer 3. Read headers and byte buffer from big buffer 4. Set headers and buffer in msg 5. Pass msg up the stack

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handleConfigEvent

void handleConfigEvent(java.util.HashMap map)

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> jgroups >> [ protocols overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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