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

---

org.jgroups.protocols
Class FRAG2  

java.lang.Object
  org.jgroups.stack.Protocol
      org.jgroups.protocols.FRAG2

---

public class FRAG2

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 FRAG2 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.
Compared to FRAG, this protocol does not need to serialize the message in order to break it into smaller fragments: it looks only at the message's buffer, which is a byte[] array anyway. We assume that the size addition for headers and src and dest address is minimal when the transport finally has to serialize the message, so we add a constant (1000 bytes).

Version:

$Id: FRAG2.java,v 1.20 2005/08/11 12:43:47 belaban Exp $

---

Nested Class Summary
(package private) static class	FRAG2.FragmentationList           A fragmentation list keeps a list of fragmentation tables sorted by an Address ( the sender ).
(package private) static class	FRAG2.FragmentationTable           Keeps track of the fragments that are received.

 

Field Summary
private  int	curr_id
(package private)  int	frag_size           The max number of bytes in a message.
private  FRAG2.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
(package private)  int	overhead           Number of bytes that we think the headers plus src and dest will take up when message is serialized by transport.

 

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

FRAG2()

 

Method Summary
void	down(org.jgroups.Event evt)           Fragment a packet if larger than frag_size (add a header).
(package private)  void	fragment(org.jgroups.Message msg)           Send all fragments as separate messages (with same ID !).
int	getFragSize()
java.lang.String	getName()
(package private)  int	getNextId()
long	getNumberOfReceivedFragments()
long	getNumberOfReceivedMessages()
long	getNumberOfSentFragments()
long	getNumberOfSentMessages()
int	getOverhead()
(package private)  void	handleConfigEvent(java.util.HashMap map)
void	resetStats()
void	setFragSize(int s)
void	setOverhead(int o)
boolean	setProperties(java.util.Properties props)           Setup the Protocol instance acording to the configuration string
(package 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

int frag_size

The max number of bytes in a message. If a message's buffer is bigger, it will be fragmented

---

overhead

int overhead

Number of bytes that we think the headers plus src and dest will take up when message is serialized by transport. This will be subtracted from frag_size

---

fragment_list

private final FRAG2.FragmentationList fragment_list

---

curr_id

private int curr_id

---

members

private final java.util.Vector members

---

name

private static final java.lang.String name

See Also:

Constant Field Values

---

num_sent_msgs

long num_sent_msgs

---

num_sent_frags

long num_sent_frags

---

num_received_msgs

long num_received_msgs

---

num_received_frags

long num_received_frags

Constructor Detail

FRAG2

public FRAG2()

Method Detail

getName

public final java.lang.String getName()

---

getFragSize

public int getFragSize()

---

setFragSize

public void setFragSize(int s)

---

getOverhead

public int getOverhead()

---

setOverhead

public void setOverhead(int o)

---

getNumberOfSentMessages

public long getNumberOfSentMessages()

---

getNumberOfSentFragments

public long getNumberOfSentFragments()

---

getNumberOfReceivedMessages

public long getNumberOfReceivedMessages()

---

getNumberOfReceivedFragments

public long getNumberOfReceivedFragments()

---

getNextId

int getNextId()

---

setProperties

public boolean setProperties(java.util.Properties props)

Setup the Protocol instance acording to the configuration string

---

resetStats

public void resetStats()

---

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 !

---

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.

---

fragment

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}
     

---

unfragment

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

---

handleConfigEvent

void handleConfigEvent(java.util.HashMap map)

---

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

---