org.jgroups.stack

Class Retransmitter


public class Retransmitter
extends java.lang.Object

Maintains a pool of sequence numbers of messages that need to be retransmitted. Messages are aged and retransmission requests sent according to age (linear backoff used). 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 a range of 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.

Version:
$Revision: 1.4 $

Authors:
John Giorgiadis
Bela Ban

Nested Class Summary

static interface
Retransmitter.RetransmitCommand
Retransmit command (see Gamma et al.) used to retrieve missing messages

Field Summary

protected static Log
log

Constructor Summary

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

Method Summary

void
add(long first_seqno, long last_seqno)
Add the given range [first_seqno, last_seqno] in the list of entries eligible for retransmission.
static void
main(String[] args)
void
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
void
setRetransmitTimeouts(long[] timeouts)
void
stop()
Stop the rentransmition and clear all pending msgs.
String
toString()

Field Details

log

protected static Log log

Constructor Details

Retransmitter

public Retransmitter(Address sender,
                     Retransmitter.RetransmitCommand cmd)
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


Retransmitter

public Retransmitter(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

If retransmitter thread is suspended, wake it up TODO: Does not check for duplicates !


main

public static void main(String[] args)


remove

public void 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


reset

public void reset()
Reset the retransmitter: clear all msgs and cancel all the respective tasks


setRetransmitTimeouts

public void setRetransmitTimeouts(long[] timeouts)


stop

public void stop()
Stop the rentransmition and clear all pending msgs.

If this retransmitter has been provided an externally managed scheduler, then just clear all msgs and the associated tasks, else stop the scheduler. In this case the method blocks until the scheduler's thread is dead. Only the owner of the scheduler should stop it.


toString

public String toString()


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