org.jgroups.stack

## Class AckMcastSenderWindow

- java.lang.Object
- - org.jgroups.stack.AckMcastSenderWindow

    public class AckMcastSenderWindow
    extends java.lang.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
`static interface` `AckMcastSenderWindow.RetransmitCommand` Called by retransmitter thread whenever a message needs to be re-sent to a destination.

### Field Summary

Fields
`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

Methods
`void` `ack(long seqno, Address sender)` An ACK has been received from `sender`.
`void` `add(long seqno, Message msg, java.util.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
`java.util.List` `getStableMessages()`
`java.lang.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.
`java.lang.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:
  `java.lang.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:
  `java.lang.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:
  `java.lang.IllegalArgumentException` - if `cmd` is null

#### AckMcastSenderWindow

    public AckMcastSenderWindow(AckMcastSenderWindow.RetransmitCommand cmd)

Create and start the retransmitter

Parameters:
  `cmd` - the callback object for retranmissions
Throws:
  `java.lang.IllegalArgumentException` - if `cmd` is null

### Method Detail

#### add

    public void add(long seqno,
           Message msg,
           java.util.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 java.util.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 java.lang.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 java.lang.String toString()

Overrides:
  `toString` in class `java.lang.Object`