Package org.jgroups.protocols
Class FC
- java.lang.Object
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- org.jgroups.stack.Protocol
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- org.jgroups.protocols.FC
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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
Changes (Brian) April 2006:- Receivers now send credits to a sender when more than min_credits have been received (rather than when min_credits are left)
- Receivers don't send the full credits (max_credits), but rather tha actual number of bytes received
- Version:
- $Id: FC.java,v 1.90.2.6 2009/03/30 14:05:22 belaban Exp $
- Author:
- Bela Ban
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
FC.FcHeader
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Constructor Summary
Constructors Constructor Description FC()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Object
down(Event evt)
An event is to be sent down the stack.java.util.Map<java.lang.String,java.lang.Object>
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()
java.lang.String
printCredits()
java.lang.String
printReceiverCredits()
java.lang.String
printSenderCredits()
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 aChannel.connect(String)
.void
stop()
This method is called on aChannel.disconnect()
.void
unblock()
Allows to unblock a blocked sender from an external program, e.g.java.lang.Object
up(Event evt)
An event was received from the layer below.-
Methods inherited from class org.jgroups.stack.Protocol
destroy, downThreadEnabled, enableStats, getDownProtocol, getProperties, getProtocolStack, getThreadFactory, getTransport, getUpProtocol, init, printStats, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, setDownProtocol, setPropertiesInternal, setProtocolStack, setUpProtocol, statsEnabled, upThreadEnabled
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Method Detail
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resetStats
public void resetStats()
- Overrides:
resetStats
in classProtocol
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getMaxCredits
public long getMaxCredits()
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setMaxCredits
public void setMaxCredits(long max_credits)
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getMinThreshold
public double getMinThreshold()
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setMinThreshold
public void setMinThreshold(double min_threshold)
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getMinCredits
public long getMinCredits()
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setMinCredits
public void setMinCredits(long min_credits)
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getNumberOfBlockings
public int getNumberOfBlockings()
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getMaxBlockTime
public long getMaxBlockTime()
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setMaxBlockTime
public void setMaxBlockTime(long t)
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getTotalTimeBlocked
public long getTotalTimeBlocked()
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getAverageTimeBlocked
public double getAverageTimeBlocked()
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getNumberOfCreditRequestsReceived
public int getNumberOfCreditRequestsReceived()
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getNumberOfCreditRequestsSent
public int getNumberOfCreditRequestsSent()
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getNumberOfCreditResponsesReceived
public int getNumberOfCreditResponsesReceived()
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getNumberOfCreditResponsesSent
public int getNumberOfCreditResponsesSent()
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printSenderCredits
public java.lang.String printSenderCredits()
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printReceiverCredits
public java.lang.String printReceiverCredits()
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printCredits
public java.lang.String printCredits()
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dumpStats
public java.util.Map<java.lang.String,java.lang.Object> dumpStats()
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showLastBlockingTimes
public java.lang.String showLastBlockingTimes()
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unblock
public void unblock()
Allows to unblock a blocked sender from an external program, e.g. JMX
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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 classProtocol
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start
public void start() throws java.lang.Exception
Description copied from class:Protocol
This method is called on aChannel.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 classProtocol
- Throws:
java.lang.Exception
- Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, soChannel.connect(String)
will throw an exception
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stop
public void stop()
Description copied from class:Protocol
This method is called on aChannel.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
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down
public java.lang.Object 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 usingdown_prot.down()
. 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 usingup_prot.up()
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up
public java.lang.Object 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 usingdown_prot.down()
or c) the event (or another event) is sent up the stack usingup_prot.up()
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