[jboss-jira] [JBoss JIRA] Commented: (JGRP-716) TCP based configs need UNICAST for correct ordering

[Bela Ban (JIRA)]

    [ http://jira.jboss.com/jira/browse/JGRP-716?page=comments#action_12406162 ] 
            
Bela Ban commented on JGRP-716:
-------------------------------

Addition: retransmission should be turned *off* in UNICAST if TCP is used (depends on JGRP-717)

> TCP based configs need UNICAST for correct ordering
> ---------------------------------------------------
>
>                 Key: JGRP-716
>                 URL: http://jira.jboss.com/jira/browse/JGRP-716
>             Project: JGroups
>          Issue Type: Task
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>             Fix For: 2.6.3, 2.7
>
>
> In a TCP based config *without* UNICAST, messages can get delivered out of order if a thread pool is enabled at the transport level. Example:
> - Sender A sends unicast messages (same for multicast messages) M1, M2 and M3 to B
> - B's transport dispatches the 3 messages to a thread pool (if bundling is enabled, then this issue might not occur as all 3 messages might have gotten bundled, and will then get delivered as a bundle, by the same thread)
> - M1 is processed by thread-1, M2 by thread-2 and M3 by thread-3
> ==> There are no guarantees with respect to ordering now, as thread pool destroyed ordering and there is no UNICAST to make sure messages arriving in different threads get ordered accoring to sequence number
> TODO: ship all TCP based protocols with UNICAST
> WORKAROUND: disable the thread pool(s) in the TCP transport

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