[jboss-jira] [JBoss JIRA] Resolved: (JGRP-341) Extend FLUSH to fully support virtual synchrony

Tue Apr 3 05:07:58 EDT 2007

     [ http://jira.jboss.com/jira/browse/JGRP-341?page=all ]

Vladimir Blagojevic resolved JGRP-341.
--------------------------------------

    Resolution: Done

We added Flush reconciliation message phase. Event REBROADCAST indicates messages that need to be retransnmitted in order to satisfy virtual synchrony. FLUSH has been updated as well as NAKACK. 

> Extend FLUSH to fully support virtual synchrony
> -----------------------------------------------
>
>                 Key: JGRP-341
>                 URL: http://jira.jboss.com/jira/browse/JGRP-341
>             Project: JGroups
>          Issue Type: Feature Request
>    Affects Versions: 2.4
>            Reporter: Bela Ban
>         Assigned To: Vladimir Blagojevic
>            Priority: Critical
>             Fix For: 2.5
>
>
> Currently, FLUSH makes sure that all members 'flush' their pending messages and then stop sending new ones until the join or state transfer is over. However, FLUSH does *not* (unlike the old version) make sure that - on JOIN -  all members have seen the same set of messages before installing a new view. Example: P sends M, but immediately after sending M crashes. If another member Q received M, but R didn't see M, then - with the current FLUSH - R will *not* see M.
> We need to run a messages exchange phase, as part of FLUSH, which makes sure that all member have seen the same set of messages in the same view, before installing a new view. Whether to run this or not could be made configurable. If enabled, we could piggyback the message exchange on START_FLUSH/FLUSH_OK etc.
> A simple (but costly) solution would be to simply multicast all messages received from other members before multicasting the FLUSH_OK. A better solution would be to exchange digests with highest sequence numbers seen for all members, and then only multicast the missing messages. This *might* require an additional phase though.

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