[jboss-jira] [JBoss JIRA] Resolved: (JGRP-402) Simple Flow Control (SFC)

[Bela Ban (JIRA)]

     [ http://jira.jboss.com/jira/browse/JGRP-402?page=all ]

Bela Ban resolved JGRP-402.
---------------------------

    Resolution: Done

Documentation is at http://www.jgroups.org/javagroupsnew/docs/manual/html/index.html (chapter 6)

> Simple Flow Control (SFC)
> -------------------------
>
>                 Key: JGRP-402
>                 URL: http://jira.jboss.com/jira/browse/JGRP-402
>             Project: JGroups
>          Issue Type: Feature Request
>    Affects Versions: 2.4
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>             Fix For: 2.5
>
>
> SFC is a simple flow control protocol for group (= multipoint) messages.
> Every sender has max_credits bytes for sending multicast messages to the group.
> Every multicast message (we don't consider unicast messages) decrements max_credits by its size.
> When max_credits falls below 0, the sender asks all receivers for new credits and blocks
> until *all* credits have been received from all members.
> When the receiver receives a credit request, it checks whether it has received max_credits bytes from the requester since
> the last credit request. If yes, it sends new credits to the requester and resets the max_credits for the requester.
> Else, it takes a note of the credit request from P and - when max_credits bytes have finally been received from P - it
> sends the credits to P and resets max_credits for P.
> The maximum amount of memory for received messages is therefore <number of senders> * max_credits.
> The relationship with STABLE is as follows: when a member Q is slow, it will prevent STABLE from collecting messages above
> the ones seen by Q (everybody else has seen more messages). However, because Q will *not* send credits back to the senders
> until it has processed all messages worth max_credits bytes, the senders will block. This in turn allows STABLE to
> progress and eventually garbage collect most messages from all senders. Therefore, SFC and STABLE complement each other,
> with SFC blocking senders so that STABLE can catch up.
> See doc/design/SimpleFlowControl.txt for details

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