org.jgroups.protocols
Class FC

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

public class FC
extends 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

Version:
$Revision: 1.50 $
Author:
Bela Ban

Nested Class Summary
static class FC.FcHeader
           
 
Field Summary
 
Fields inherited from class org.jgroups.stack.Protocol
down_handler, down_prot, down_queue, down_thread, down_thread_prio, log, observer, props, stack, stats, trace, up_handler, up_prot, up_queue, up_thread, up_thread_prio, warn
 
Constructor Summary
FC()
           
 
Method Summary
 void down(Event evt)
          An event is to be sent down the stack.
 java.util.Map dumpStats()
           
 double getAverageTimeBlocked()
           
 long getMaxBlockTime()
           
 long getMaxCredits()
           
 long getMinCredits()
           
 double getMinThreshold()
           
 java.lang.String getName()
           
 int getNumberOfBlockings()
           
 int getNumberOfCreditRequestsReceived()
           
 int getNumberOfCreditRequestsSent()
           
 int getNumberOfCreditResponsesReceived()
           
 int getNumberOfCreditResponsesSent()
           
 long getTotalTimeBlocked()
           
 boolean isBlocked()
           
 java.lang.String printCredits()
           
 java.lang.String printReceiverCredits()
           
 java.lang.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.
 void resetStats()
           
 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)
          Configures the protocol initially.
 java.lang.String showLastBlockingTimes()
           
 void start()
          This method is called on a Channel.connect(String).
 void stop()
          This method is called on a Channel.disconnect().
 void unblock()
          Allows to unblock a blocked sender from an external program, e.g.
 void up(Event evt)
          An event was received from the layer below.
 
Methods inherited from class org.jgroups.stack.Protocol
destroy, downThreadEnabled, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, isTrace, isWarn, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveUpEvent, requiredDownServices, requiredUpServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setTrace, setUpProtocol, setWarn, startDownHandler, startUpHandler, statsEnabled, stopInternal, 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

getName

public final java.lang.String getName()
Specified by:
getName in class Protocol

resetStats

public void resetStats()
Overrides:
resetStats in class Protocol

getMaxCredits

public long getMaxCredits()

setMaxCredits

public void setMaxCredits(long max_credits)

getMinThreshold

public double getMinThreshold()

setMinThreshold

public void setMinThreshold(double min_threshold)

getMinCredits

public long getMinCredits()

setMinCredits

public void setMinCredits(long min_credits)

isBlocked

public boolean isBlocked()

getNumberOfBlockings

public int getNumberOfBlockings()

getMaxBlockTime

public long getMaxBlockTime()

setMaxBlockTime

public void setMaxBlockTime(long t)

getTotalTimeBlocked

public long getTotalTimeBlocked()

getAverageTimeBlocked

public double getAverageTimeBlocked()

getNumberOfCreditRequestsReceived

public int getNumberOfCreditRequestsReceived()

getNumberOfCreditRequestsSent

public int getNumberOfCreditRequestsSent()

getNumberOfCreditResponsesReceived

public int getNumberOfCreditResponsesReceived()

getNumberOfCreditResponsesSent

public int getNumberOfCreditResponsesSent()

printSenderCredits

public java.lang.String printSenderCredits()

printReceiverCredits

public java.lang.String printReceiverCredits()

printCredits

public java.lang.String printCredits()

dumpStats

public java.util.Map dumpStats()
Overrides:
dumpStats in class Protocol

showLastBlockingTimes

public java.lang.String showLastBlockingTimes()

unblock

public void unblock()
Allows to unblock a blocked sender from an external program, e.g. JMX


setProperties

public boolean setProperties(java.util.Properties props)
Description copied from class: Protocol
Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:
 "loopback=false;unicast_inport=4444"
 

Overrides:
setProperties in class Protocol

start

public void start()
           throws java.lang.Exception
Description copied from class: Protocol
This method is called on a Channel.connect(String). Starts work. Protocols are connected and queues are ready to receive events. Will be called from bottom to top. This call will replace the START and START_OK events.

Overrides:
start in class Protocol
Throws:
java.lang.Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception

stop

public void stop()
Description copied from class: Protocol
This method is called on a Channel.disconnect(). Stops work (e.g. by closing multicast socket). Will be called from top to bottom. This means that at the time of the method invocation the neighbor protocol below is still working. This method will replace the STOP, STOP_OK, CLEANUP and CLEANUP_OK events. The ProtocolStack guarantees that when this method is called all messages in the down queue will have been flushed

Overrides:
stop in class Protocol

receiveDownEvent

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. However, if member P crashed, we need to unblock !

Overrides:
receiveDownEvent in class Protocol
Parameters:
evt -

down

public void down(Event evt)
Description copied from class: Protocol
An event is to be sent down the stack. The layer may want to examine its type and perform some action on it, depending on the event's type. If the event is a message MSG, then the layer may need to add a header to it (or do nothing at all) before sending it down the stack using passDown(). In case of a GET_ADDRESS event (which tries to retrieve the stack's address from one of the bottom layers), the layer may need to send a new response event back up the stack using passUp().

Overrides:
down in class Protocol

up

public void up(Event evt)
Description copied from class: Protocol
An event was received from the layer below. Usually the current layer will want to examine the event type and - depending on its type - perform some computation (e.g. removing headers from a MSG event type, or updating the internal membership list when receiving a VIEW_CHANGE event). Finally the event is either a) discarded, or b) an event is sent down the stack using passDown() or c) the event (or another event) is sent up the stack using passUp().

Overrides:
up in class Protocol


Copyright ? 1998-2005 Bela Ban. All Rights Reserved.