[jboss-jira] [JBoss JIRA] Commented: (JGRP-607) SEQUENCER: incorrect ordering on concurrent sends

[Bela Ban (JIRA)]

    [ http://jira.jboss.com/jira/browse/JGRP-607?page=comments#action_12384051 ] 
            
Bela Ban commented on JGRP-607:
-------------------------------

The bug is that, when we don't send seqnos in order, then the receiver will always keep the highest seqno, e.g. when we send
1 2 4 3, then - when 4 is received - the highest seqno will be 4 (regardless of whether there is a gap since we haven't yet received 3), and when 3 is finally received, it will get discarded.
Solution: maintain the highest received and highest delivered seqno (SeqnoTable)

Even if we synchronized down(), this wouldn't help, as 3 and 4 will get sent out in order, but a message loss of 3 might still cause receivers to receive 4 first and then the (retransmitted) 3.

> SEQUENCER: incorrect ordering on concurrent sends
> -------------------------------------------------
>
>                 Key: JGRP-607
>                 URL: http://jira.jboss.com/jira/browse/JGRP-607
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>             Fix For: 2.6, 2.4.1 SP5, 2.5.2
>
>
> The unit test which fails is SequencerOrderTest. With SEQUENCER.down() synchronized, the test always passes

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