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

### Method Summary

Methods
`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()`
`java.lang.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 Detail

#### 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 Detail

#### 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 java.lang.String toString()

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

#### size

    public int size()

Specified by:
  `size` in class `Retransmitter`