org.jgroups.stack

Class AckMcastSenderWindow

java.lang.Object

org.jgroups.stack.AckMcastSenderWindow

public class AckMcastSenderWindow
extends Object

Keeps track of ACKs from receivers for each message. When a new message is sent, it is tagged with a sequence number and the receiver set (set of members to which the message is sent) and added to a hashtable (key = sequence number, val = message + receiver set). Each incoming ACK is noted and when all ACKs for a specific sequence number haven been received, the corresponding entry is removed from the hashtable. A retransmission thread periodically re-sends the message point-to-point to all receivers from which no ACKs have been received yet. A view change or suspect message causes the corresponding non-existing receivers to be removed from the hashtable.

This class may need flow control in order to avoid needless retransmissions because of timeouts.

Author:

Bela Ban June 9 1999, 2007, John Georgiadis May 8 2001

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	AckMcastSenderWindow.RetransmitCommand Called by retransmitter thread whenever a message needs to be re-sent to a destination.

Field Summary

Fields

Modifier and Type	Field and Description
protected static Log	log Default retransmit thread suspend timeout (ms)

Constructor Summary

Constructors

Constructor and Description
AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd) Create and start the retransmitter
AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd, Interval retransmit_intervals) Create and start the retransmitter
AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd, Interval retransmit_intervals, TimeScheduler sched) Create and start the retransmitter
AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd, TimeScheduler sched) Create and start the retransmitter

Method Summary

Modifier and Type	Method and Description
void	ack(long seqno, Address sender) An ACK has been received from sender.
void	add(long seqno, Message msg, Vector receivers) Adds a new message to the hash table.
void	clearStableMessages()
long	getNumberOfResponsesExpected(long seqno) Returns the number of members for a given entry for which acks have to be received
long	getNumberOfResponsesReceived(long seqno) Returns the number of members for a given entry for which acks have been received
List	getStableMessages()
String	printDetails(long seqno) Prints all members plus whether an ack has been received from those members for a given seqno
void	remove(Address obj) Remove obj from all receiver sets and wake up retransmission thread.
void	reset() Remove all pending msgs from the hashtable.
long	size()
void	stop() Stop the rentransmition and clear all pending msgs.
void	suspect(Address suspected) Process with address suspected is suspected: remove it from all receiver sets.
String	toString()
void	waitUntilAllAcksReceived(long timeout) Waits until all outstanding messages have been ACKed by all receivers.

Methods inherited from class java.lang.Object

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

Field Detail

log

protected static final Log log

Default retransmit thread suspend timeout (ms)

Constructor Detail

AckMcastSenderWindow

public AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd,
                            Interval retransmit_intervals,
                            TimeScheduler sched)

Create and start the retransmitter

Parameters:

cmd - the callback object for retranmissions

retransmit_intervals - the interval between two consecutive retransmission attempts

sched - the external scheduler to use to schedule retransmissions

Throws:

IllegalArgumentException - if cmd is null

AckMcastSenderWindow

public AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd,
                            TimeScheduler sched)

Create and start the retransmitter

Parameters:

cmd - the callback object for retranmissions

sched - the external scheduler to use to schedule retransmissions

Throws:

IllegalArgumentException - if cmd is null

AckMcastSenderWindow

public AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd,
                            Interval retransmit_intervals)

Create and start the retransmitter

Parameters:

cmd - the callback object for retranmissions

retransmit_intervals - the interval between two consecutive retransmission attempts

Throws:

IllegalArgumentException - if cmd is null

AckMcastSenderWindow

public AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd)

Create and start the retransmitter

Parameters:

cmd - the callback object for retranmissions

Throws:

IllegalArgumentException - if cmd is null

Method Detail

add

public void add(long seqno,
                Message msg,
                Vector receivers)

Adds a new message to the hash table.

Parameters:

seqno - The sequence number associated with the message

msg - The message (should be a copy!)

receivers - The set of addresses to which the message was sent and from which consequently an ACK is expected

ack

public void ack(long seqno,
                Address sender)

An ACK has been received from sender. Tag the sender in the hash table as 'received'. If all ACKs have been received, remove the entry all together.

Parameters:

seqno - The sequence number of the message for which an ACK has been received.

sender - The sender which sent the ACK

remove

public void remove(Address obj)

Remove obj from all receiver sets and wake up retransmission thread.

Parameters:

obj - the sender to remove

suspect

public void suspect(Address suspected)

Process with address suspected is suspected: remove it from all receiver sets. This means that no ACKs are expected from this process anymore.

Parameters:

suspected - The suspected process

getStableMessages

public List getStableMessages()

Returns:

a copy of stable messages, or null (if non available). Removes all stable messages afterwards

clearStableMessages

public void clearStableMessages()

size

public long size()

Returns:

the number of currently pending msgs

getNumberOfResponsesExpected

public long getNumberOfResponsesExpected(long seqno)

Returns the number of members for a given entry for which acks have to be received

getNumberOfResponsesReceived

public long getNumberOfResponsesReceived(long seqno)

Returns the number of members for a given entry for which acks have been received

printDetails

public String printDetails(long seqno)

Prints all members plus whether an ack has been received from those members for a given seqno

waitUntilAllAcksReceived

public void waitUntilAllAcksReceived(long timeout)

Waits until all outstanding messages have been ACKed by all receivers. Takes into account suspicions and view changes. Returns when there are no entries left in the hashtable. While waiting, no entries can be added to the hashtable (they will be discarded).

Parameters:

timeout - Miliseconds to wait. 0 means wait indefinitely.

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.

reset

public void reset()

Remove all pending msgs from the hashtable. Cancel all associated tasks in the retransmission scheduler

toString

public String toString()

Overrides:

toString in class Object