Package org.jgroups.stack

Class DefaultRetransmitter

java.lang.Object

org.jgroups.stack.Retransmitter

org.jgroups.stack.DefaultRetransmitter

public class DefaultRetransmitter
extends Retransmitter

Maintains a pool of sequence numbers of messages that need to be retransmitted. Messages are aged and retransmission requests sent according to age (configurable backoff). If a TimeScheduler instance is given to the constructor, it will be used, otherwise Reransmitter will create its own. The retransmit timeouts have to be set first thing after creating an instance. The add() method adds the sequence numbers of messages to be retransmitted. The remove() method removes a sequence number again, cancelling retransmission requests for it. Whenever a message needs to be retransmitted, the RetransmitCommand.retransmit() method is called. It can be used e.g. by an ack-based scheme (e.g. AckSenderWindow) to retransmit a message to the receiver, or by a nak-based scheme to send a retransmission request to the sender of the missing message.
Changes Aug 2007 (bela): the retransmitter was completely rewritten. Entry was removed, instead all tasks are directly placed into a hashmap, keyed by seqnos. When a message has been received, we simply remove the task from the hashmap and cancel it. This simplifies the code and avoids having to iterate through the (previous) message list linearly on removal. Performance is about the same, or slightly better in informal tests.

Version:

$Revision: 1.4 $

Author:

Bela Ban

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected class	DefaultRetransmitter.SeqnoTask

Nested classes/interfaces inherited from class org.jgroups.stack.Retransmitter

Retransmitter.RetransmitCommand, Retransmitter.Task

Field Summary

Fields inherited from class org.jgroups.stack.Retransmitter

cmd, log, RETRANSMIT_TIMEOUTS, sender, timer

Constructor Summary

Constructors

Constructor	Description
DefaultRetransmitter(Address sender, Retransmitter.RetransmitCommand cmd, TimeScheduler sched)	Create a new Retransmitter associated with the given sender address

Method Summary

Modifier and Type	Method	Description
void	add(long first_seqno, long last_seqno)	Add the given range [first_seqno, last_seqno] in the list of entries eligible for retransmission.
int	remove(long seqno)	Remove the given sequence number from the list of seqnos eligible for retransmission.
void	reset()	Reset the retransmitter: clear all msgs and cancel all the respective tasks
int	size()
String	toString()

Methods inherited from class org.jgroups.stack.Retransmitter

setRetransmitTimeouts

Methods inherited from class java.lang.Object

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

Constructor Details

DefaultRetransmitter

public DefaultRetransmitter(Address sender,
 Retransmitter.RetransmitCommand cmd,
 TimeScheduler sched)

Create a new Retransmitter associated with the given sender address

Parameters:

sender - the address from which retransmissions are expected or to which retransmissions are sent

cmd - the retransmission callback reference

sched - retransmissions scheduler

Method Details

add

public void add(long first_seqno,
 long last_seqno)

Add the given range [first_seqno, last_seqno] in the list of entries eligible for retransmission. If first_seqno > last_seqno, then the range [last_seqno, first_seqno] is added instead

Specified by:

add in class Retransmitter

remove

public int remove(long seqno)

Remove the given sequence number from the list of seqnos eligible for retransmission. If there are no more seqno intervals in the respective entry, cancel the entry from the retransmission scheduler and remove it from the pending entries

Specified by:

remove in class Retransmitter

reset

public void reset()

Reset the retransmitter: clear all msgs and cancel all the respective tasks

Specified by:

reset in class Retransmitter

toString

public String toString()

Overrides:

toString in class Object

size

public int size()

Specified by:

size in class Retransmitter