org.jgroups.protocols
Class FC

java.lang.Object
  org.jgroups.stack.Protocol
      org.jgroups.protocols.FC

public class FC
extends org.jgroups.stack.Protocol

Simple flow control protocol based on a credit system. Each sender has a number of credits (bytes to send). When the credits have been exhausted, the sender blocks. Each receiver also keeps track of how many credits it has received from a sender. When credits for a sender fall below a threshold, the receiver sends more credits to the sender. Works for both unicast and multicast messages.

Note that this protocol must be located towards the top of the stack, or all down_threads from JChannel to this protocol must be set to false ! This is in order to block JChannel.send()/JChannel.down().
This is the second simplified implementation of the same model. The algorithm is sketched out in doc/FlowControl.txt
Changes (Brian) April 2006:

1. Receivers now send credits to a sender when more than min_credits have been received (rather than when min_credits are left)
2. Receivers don't send the full credits (max_credits), but rather tha actual number of bytes received

   Version:

   $Id: FC.java,v 1.86.2.1 2007/12/18 07:58:17 belaban Exp $

   Author:

   Bela Ban

   Nested Class Summary

   static class

   FC.FcHeader

   Field Summary

   Fields inherited from class org.jgroups.stack.Protocol

   down_prot, log, props, stack, stats, up_prot

   Constructor Summary

   FC()
   

   Method Summary

   java.lang.Object	down(org.jgroups.Event evt)
   java.util.Map<java.lang.String,java.lang.Object>	dumpStats()
   double	getAverageTimeBlocked()
   long	getLowest_max_credits()
   long	getMaxBlockTime()
   long	getMaxCredits()
   long	getMinCredits()
   double	getMinThreshold()
   java.lang.String	getName()
   int	getNumberOfBlockings()
   int	getNumberOfCreditRequestsReceived()
   int	getNumberOfCreditRequestsSent()
   int	getNumberOfCreditResponsesReceived()
   int	getNumberOfCreditResponsesSent()
   long	getTotalTimeBlocked()
   java.lang.String	printCredits()
   java.lang.String	printReceiverCredits()
   java.lang.String	printSenderCredits()
   void	resetStats()
   void	setLowest_max_credits(long lowest_max_credits)
   void	setMaxBlockTime(long t)
   void	setMaxCredits(long max_credits)
   void	setMinCredits(long min_credits)
   void	setMinThreshold(double min_threshold)
   boolean	setProperties(java.util.Properties props)
   java.lang.String	showLastBlockingTimes()
   void	start()
   void	stop()
   void	unblock() Allows to unblock a blocked sender from an external program, e.g.
   java.lang.Object	up(org.jgroups.Event evt)

   Methods inherited from class org.jgroups.stack.Protocol

   destroy, downThreadEnabled, enableStats, getDownProtocol, getProperties, getUpProtocol, init, printStats, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, setDownProtocol, setPropertiesInternal, setProtocolStack, setUpProtocol, statsEnabled, upThreadEnabled

   Methods inherited from class java.lang.Object

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

   Constructor Detail

   FC

   public FC()

   Method Detail

   down

   public java.lang.Object down(org.jgroups.Event evt)

   Overrides:

   down in class org.jgroups.stack.Protocol

   dumpStats

   public java.util.Map<java.lang.String,java.lang.Object> dumpStats()

   Overrides:

   dumpStats in class org.jgroups.stack.Protocol

   getAverageTimeBlocked

   public double getAverageTimeBlocked()

   getLowest_max_credits

   public long getLowest_max_credits()

   getMaxBlockTime

   public long getMaxBlockTime()

   getMaxCredits

   public long getMaxCredits()

   getMinCredits

   public long getMinCredits()

   getMinThreshold

   public double getMinThreshold()

   getName

   public final java.lang.String getName()

   Specified by:

   getName in class org.jgroups.stack.Protocol

   getNumberOfBlockings

   public int getNumberOfBlockings()

   getNumberOfCreditRequestsReceived

   public int getNumberOfCreditRequestsReceived()

   getNumberOfCreditRequestsSent

   public int getNumberOfCreditRequestsSent()

   getNumberOfCreditResponsesReceived

   public int getNumberOfCreditResponsesReceived()

   getNumberOfCreditResponsesSent

   public int getNumberOfCreditResponsesSent()

   getTotalTimeBlocked

   public long getTotalTimeBlocked()

   printCredits

   public java.lang.String printCredits()

   printReceiverCredits

   public java.lang.String printReceiverCredits()

   printSenderCredits

   public java.lang.String printSenderCredits()

   resetStats

   public void resetStats()

   Overrides:

   resetStats in class org.jgroups.stack.Protocol

   setLowest_max_credits

   public void setLowest_max_credits(long lowest_max_credits)

   setMaxBlockTime

   public void setMaxBlockTime(long t)

   setMaxCredits

   public void setMaxCredits(long max_credits)

   setMinCredits

   public void setMinCredits(long min_credits)

   setMinThreshold

   public void setMinThreshold(double min_threshold)

   setProperties

   public boolean setProperties(java.util.Properties props)

   Overrides:

   setProperties in class org.jgroups.stack.Protocol

   showLastBlockingTimes

   public java.lang.String showLastBlockingTimes()

   start

   public void start()
              throws java.lang.Exception

   Overrides:

   start in class org.jgroups.stack.Protocol

   Throws:

   java.lang.Exception

   stop

   public void stop()

   Overrides:

   stop in class org.jgroups.stack.Protocol

   unblock

   public void unblock()

   Allows to unblock a blocked sender from an external program, e.g. JMX

   up

   public java.lang.Object up(org.jgroups.Event evt)

   Overrides:

   up in class org.jgroups.stack.Protocol