[jboss-jira] [JBoss JIRA] Resolved: (JGRP-1013) STATE_TRANSFER / STREAMING_STATE_TRANSFER: close BARRIER before applying state response

[Bela Ban (JIRA)]

     [ https://jira.jboss.org/jira/browse/JGRP-1013?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bela Ban resolved JGRP-1013.
----------------------------

    Resolution: Done


Fixed according to suggested solution

> STATE_TRANSFER / STREAMING_STATE_TRANSFER: close BARRIER before applying state response
> ---------------------------------------------------------------------------------------
>
>                 Key: JGRP-1013
>                 URL: https://jira.jboss.org/jira/browse/JGRP-1013
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 2.6.11, 2.8
>
>
> Current, both state transfer protocols close the barrier, process the state *request* and re-open it. However, this is NOT done for state *responses* !
> The following issue could happen:
> - D requests the state from A
> - B multicasts #11
> - D receives the digest A:5, B:10, C:44 and (in parallel) B:11
> Scenario #1:
> - [NAKACK] D applies the digest (is 10 for B)
> - [NAKACK] D receives B:11 (is 11 now for B)
> - D delivers B:11 to the app, changes state
> - D sets state, overwrites the change made by B:11
> --> B:11 will *not* get retransmitted as the digest in NAKACK already has it: the change made by B:11 is lost !
> Scenario #2:
> - [NAKACK] D receives B:11 (is 11 now for B)
> - [NAKACK] D applies the digest: resets the digest for B to #10
> - D sets state
> - D delivers B:11 to the app, changes state
> --> B:11 will get retransmitted as the digest in NAKACK doesn't contain it
> --> B:11 changes state *again*: B:11 is delivered *twice* !
> So scenario #1 loses B:11 while scenario #2 delivers B:11 twice, which has to be prevented.
> SOLUTION: 
> - Close BARRIER before state response is handled (similar to what we do with a state request)
> - This way, either B:11 is handled and changes the digest in NAKACK and the app state *before* we set the digest in NAKACK and the app state, OR the digest is set in NAKACK and the app state is set from the state response and THEN B:11 is handled

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