Package org.jgroups.protocols

Class UFC

java.lang.Object

org.jgroups.stack.Protocol

org.jgroups.protocols.FlowControl

org.jgroups.protocols.UFC

All Implemented Interfaces:

Lifecycle

Direct Known Subclasses:

UFC_NB

public class UFC
extends FlowControl

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 the actual number of bytes received

Field Summary

Fields

Modifier and Type	Field	Description
protected final Map<Address,? extends Credit>	sent	Map: keys are members, values are credits left.
protected static final FcHeader	UFC_CREDIT_REQUEST_HDR
protected static final FcHeader	UFC_REPLENISH_HDR

Fields inherited from class org.jgroups.protocols.FlowControl

frag_size, max_block_time, max_credits, min_credits, min_threshold, num_credit_requests_received, num_credit_requests_sent, num_credit_responses_received, num_credit_responses_sent, num_msgs_dropped, received, running

Fields inherited from class org.jgroups.stack.Protocol

after_creation_hook, down_prot, ergonomics, id, local_addr, log, policies, stack, stats, up_prot

Constructor Summary

Constructors

Constructor	Description
UFC()

Method Summary

Modifier and Type	Method	Description
protected <T extends Credit> T	createCredit(int initial_credits)
double	getAverageTimeBlocked()
protected Header	getCreditRequestHeader()
int	getNumberOfBlockings()
protected Header	getReplenishHeader()
long	getSenderCreditsFor(Address mbr)
protected void	handleCredit(Address sender, long increase)
protected Object	handleDownMessage(Message msg, int length)
protected boolean	handleMulticastMessage()	Whether the protocol handles message with dest == null || dest.isMulticastAddress()
protected void	handleViewChange(List<Address> mbrs)
String	printCredits()
String	printSenderCredits()
void	resetStats()
void	stop()	Called on a JChannel.disconnect(); stops work (e.g.
void	unblock()	Allows to unblock all blocked senders from an external program, e.g.

Methods inherited from class org.jgroups.protocols.FlowControl

adjustCredit, down, down, getMaxBlockTime, getMaxCredits, getMinCredits, getMinThreshold, getNumberOfCreditRequestsReceived, getNumberOfCreditRequestsSent, getNumberOfCreditResponsesReceived, getNumberOfCreditResponsesSent, getReceiverCreditsFor, handleConfigEvent, handleCreditRequest, handleUpEvent, init, printMap, printReceiverCredits, sendCredit, sendCreditRequest, setMaxBlockTime, setMaxCredits, setMinCredits, setMinThreshold, start, up, up, up

Methods inherited from class org.jgroups.stack.Protocol

accept, addPolicy, addr, addr, afterCreationHook, destroy, down, enableStats, getAddress, getComponents, getDownProtocol, getDownServices, getId, getIdsAbove, getLevel, getLog, getName, getPolicies, getProtocolStack, getSocketFactory, getThreadFactory, getTransport, getUpProtocol, getUpServices, getValue, isErgonomics, level, parse, policies, providedDownServices, providedUpServices, removePolicy, requiredDownServices, requiredUpServices, resetStatistics, setAddress, setDownProtocol, setErgonomics, setId, setLevel, setPolicies, setProtocolStack, setSocketFactory, setUpProtocol, setValue, statsEnabled, toString

Methods inherited from class java.lang.Object

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

Field Details

UFC_REPLENISH_HDR

protected static final FcHeader UFC_REPLENISH_HDR

UFC_CREDIT_REQUEST_HDR

protected static final FcHeader UFC_CREDIT_REQUEST_HDR

sent

protected final Map<Address,? extends Credit> sent

Map: keys are members, values are credits left. For each send, the number of credits is decremented by the message size

Constructor Details

UFC

public UFC()

Method Details

printSenderCredits

public String printSenderCredits()

Specified by:

printSenderCredits in class FlowControl

printCredits

public String printCredits()

Overrides:

printCredits in class FlowControl

handleMulticastMessage

protected boolean handleMulticastMessage()

Description copied from class: FlowControl

Whether the protocol handles message with dest == null || dest.isMulticastAddress()

Specified by:

handleMulticastMessage in class FlowControl

getReplenishHeader

protected Header getReplenishHeader()

Specified by:

getReplenishHeader in class FlowControl

getCreditRequestHeader

protected Header getCreditRequestHeader()

Specified by:

getCreditRequestHeader in class FlowControl

unblock

public void unblock()

Description copied from class: FlowControl

Allows to unblock all blocked senders from an external program, e.g. JMX

Overrides:

unblock in class FlowControl

getSenderCreditsFor

public long getSenderCreditsFor(Address mbr)

getNumberOfBlockings

public int getNumberOfBlockings()

Specified by:

getNumberOfBlockings in class FlowControl

getAverageTimeBlocked

public double getAverageTimeBlocked()

Specified by:

getAverageTimeBlocked in class FlowControl

stop

public void stop()

Description copied from class: Protocol

Called on a JChannel.disconnect(); stops work (e.g. by closing multicast socket). Will be called from top to bottom.

Specified by:

stop in interface Lifecycle

Overrides:

stop in class FlowControl

resetStats

public void resetStats()

Overrides:

resetStats in class FlowControl

handleDownMessage

protected Object handleDownMessage(Message msg,
 int length)

Specified by:

handleDownMessage in class FlowControl

handleViewChange

protected void handleViewChange(List<Address> mbrs)

Overrides:

handleViewChange in class FlowControl

handleCredit

protected void handleCredit(Address sender,
 long increase)

Specified by:

handleCredit in class FlowControl

createCredit

protected <T extends Credit> T createCredit(int initial_credits)