FC (JGroups)

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

Version: $Revision: 1.50 $

Author: Bela Ban

Nested Class Summary
static class	FC.FcHeader

Method Summary
void	down(Event evt)
Map	dumpStats()
double	getAverageTimeBlocked()
long	getMaxBlockTime()
long	getMaxCredits()
long	getMinCredits()
double	getMinThreshold()
String	getName()
int	getNumberOfBlockings()
int	getNumberOfCreditRequestsReceived()
int	getNumberOfCreditRequestsSent()
int	getNumberOfCreditResponsesReceived()
int	getNumberOfCreditResponsesSent()
long	getTotalTimeBlocked()
boolean	isBlocked()
String	printCredits()
String	printReceiverCredits()
String	printSenderCredits()
protected void	receiveDownEvent(Event evt) We need to receive view changes concurrent to messages on the down events: a message might blocks, e.g. because we don't have enough credits to send to member P.
void	resetStats()
void	setMaxBlockTime(long t)
void	setMaxCredits(long max_credits)
void	setMinCredits(long min_credits)
void	setMinThreshold(double min_threshold)
boolean	setProperties(Properties props)
String	showLastBlockingTimes()
void	start()
void	stop()
void	unblock() Allows to unblock a blocked sender from an external program, e.g.
void	up(Event evt)

We need to receive view changes concurrent to messages on the down events: a message might blocks, e.g. because we don't have enough credits to send to member P. However, if member P crashed, we need to unblock !

Parameters: evt

Class FC

Method Detail

down

dumpStats

getAverageTimeBlocked

getMaxBlockTime

getMaxCredits

getMinCredits

getMinThreshold

getName

getNumberOfBlockings

getNumberOfCreditRequestsReceived

getNumberOfCreditRequestsSent

getNumberOfCreditResponsesReceived

getNumberOfCreditResponsesSent

getTotalTimeBlocked

isBlocked

printCredits

printReceiverCredits

printSenderCredits

receiveDownEvent

resetStats

setMaxBlockTime

setMaxCredits

setMinCredits

setMinThreshold

setProperties

showLastBlockingTimes

start

stop

unblock

up