Class Retransmitter

java.lang.Object
org.jgroups.stack.Retransmitter

public class Retransmitter extends Object
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: 1.23.2.1.2.1 $
Author:
Bela Ban
  • Field Details

    • log

      protected static final org.apache.commons.logging.Log log
  • Constructor Details

    • 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
    • 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
  • Method Details

    • setRetransmitTimeouts

      public void setRetransmitTimeouts(Interval interval)
    • 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

    • 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
    • reset

      public void reset()
      Reset the retransmitter: clear all msgs and cancel all the respective tasks
    • 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()
      Overrides:
      toString in class Object
    • size

      public int size()