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java.lang.Objectorg.jgroups.stack.Protocol
org.jgroups.stack.MessageProtocol
org.jgroups.protocols.FLOW_CONTROL
FLOW_CONTROL provides end-end congestion control and flow control.
Attempts to maximize through put, by minimizing the
possible block times(Forward flow control). Initially, sender starts with a smaller
window size W
and large expected RTT grpRTT
. Sender also
keeps a margin in the window size. When the margin is hit, insted of waiting for the
window size to be exhausted, sender multicasts a FLOW_CONTROL info request message.
If the window size is exhausted before the responses are received, send will be blocked.
FCInfo(flow control info) from all the receivers is gathered at the sender, and current RTT
is computed. If the current RTT is greater than estimated RTT window size and margin are reduced,
otherwise they are increased.
Horizontal interaction is initiated by the sender with the other group members.
Note: A reliable transport layer is required for this protocol to function properly. With little effort this can be made completely independent.
Field Summary |
Fields inherited from class org.jgroups.stack.MessageProtocol |
_corr, members |
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 | |
FLOW_CONTROL()
|
Method Summary | |
java.lang.String |
getName()
|
java.lang.Object |
handle(Message req)
Called when a request for this protocol layer is received. |
boolean |
handleDownEvent(Event evt)
If Event.MSG type is received count is incremented by one, and message is passed to the down_prot. |
boolean |
handleUpEvent(Event evt)
If Event.MSG type is received message, number of received messages from the sender is incremented. |
void |
run()
FCInfo request must be submitted in a different thread. |
boolean |
setProperties(java.util.Properties props)
Following parameters can be optionally supplied: window size cap - int Limits the window size to a reasonable value. |
Methods inherited from class org.jgroups.stack.MessageProtocol |
castMessage, down, sendMessage, start, stop, up, updateView |
Methods inherited from class org.jgroups.stack.Protocol |
destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, isTrace, isWarn, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, resetStats, 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 |
public FLOW_CONTROL()
Method Detail |
public java.lang.String getName()
getName
in class Protocol
public boolean handleDownEvent(Event evt)
handleDownEvent
in class MessageProtocol
public boolean handleUpEvent(Event evt)
handleUpEvent
in class MessageProtocol
public java.lang.Object handle(Message req)
handle
in interface RequestHandler
handle
in class MessageProtocol
public void run()
run
in interface java.lang.Runnable
public boolean setProperties(java.util.Properties props)
int
Limits the window size to a reasonable value.
int
these many number of messages are sent before a block could happen
int
a request for flow control information is sent when remaining window size hits this margin
double
Max RTT in the group is calculated during each Flow control request. lower number assigns
higher weight to current RTT in estimating RTT.
double
When current RTT is greater than estimated RTT current window size
is reduced by this multiple.
double
When current RTT is less than estimated RTT window is incremented
by this multiple.
setProperties
in class Protocol
Protocol.setProperties(Properties)
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