| org.jgroups.stack.MessageProtocol
 org.jgroups.protocols.FLOW_CONTROL
| FLOW_CONTROL | | public class FLOW_CONTROL extends MessageProtocol implements Runnable(Code) | | 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.
todo Handle view changes (e.g., members {A,B,C}, blocked on C, and C crashes --> unblock).
Also block on down() instead of sending BLOCK_SEND. // done, bela April 28 2006
author:
Ananda Bollu |
| Method Summary | |
| public String | getName()
| | public Object | handle(Message req)
Called when a request for this protocol layer is received.
Processes and return value is sent back in the reply.
FLOW_CONTROL protocol of all members gets this message(including sender?)
Object containing FC information for sender with senderID.Callback. | | public boolean | handleDownEvent(Event evt)
If Event.MSG type is received count is incremented by one,
and message is passed to the down_prot. | | public boolean | handleUpEvent(Event evt)
If Event.MSG type is received message, number of received
messages from the sender is incremented. | | public void | run()
FCInfo request must be submitted in a different thread.
handleDownEvent() can still be called to send messages
while waiting for FCInfo from receivers. | | public boolean | setProperties(Properties props)
Following parameters can be optionally supplied:
- window size cap -
int Limits the window size to a reasonable value.
- window size -
int these many number of messages are sent before a block could happen
- forward margin -
int a request for flow control information is sent when remaining window size hits this margin
- RTT weight -
double Max RTT in the group is calculated during each Flow control request. |
| FLOW_CONTROL | | public FLOW_CONTROL()(Code) | | |
| handle | | public Object handle(Message req)(Code) | | Called when a request for this protocol layer is received.
Processes and return value is sent back in the reply.
FLOW_CONTROL protocol of all members gets this message(including sender?)
Object containing FC information for sender with senderID.Callback. Called when a request for this protocol layer is received. |
| handleDownEvent | | public boolean handleDownEvent(Event evt)(Code) | | If Event.MSG type is received count is incremented by one,
and message is passed to the down_prot. At some point,
based on the algorithm(FLOW_CONTROL protocol definition)
data collection sequence is started. This is done by each
member in SENDER role when _numMSGsSentThisPeriod hits the margin.
Before rsp arrives only _fwdMarginSize number of messages can be sent,
and then sender will be blocked.
|
| handleUpEvent | | public boolean handleUpEvent(Event evt)(Code) | | If Event.MSG type is received message, number of received
messages from the sender is incremented. And the message is
passed up the stack.
|
| run | | public void run()(Code) | | FCInfo request must be submitted in a different thread.
handleDownEvent() can still be called to send messages
while waiting for FCInfo from receivers. usually takes
RTT.
|
| setProperties | | public boolean setProperties(Properties props)(Code) | | Following parameters can be optionally supplied:
- window size cap -
int Limits the window size to a reasonable value.
- window size -
int these many number of messages are sent before a block could happen
- forward margin -
int a request for flow control information is sent when remaining window size hits this margin
- RTT weight -
double Max RTT in the group is calculated during each Flow control request. lower number assigns
higher weight to current RTT in estimating RTT.
- window size reduction factor -
double When current RTT is greater than estimated RTT current window size
is reduced by this multiple.
- window size expansion factor -
double When current RTT is less than estimated RTT window is incremented
by this multiple.
See Also: org.jgroups.stack.Protocol.setProperties(Properties) |
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