[jboss-jira] [JBoss JIRA] Commented: (JGRP-1251) NAKACK: overwriteDigest() doesn't adjust sequence number

[Bela Ban (JIRA)]

    [ https://jira.jboss.org/browse/JGRP-1251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12562459#action_12562459 ] 

Bela Ban commented on JGRP-1251:
--------------------------------

To reproduce:

- Take udp.xml and add <DISCARD use_uid="true"/> on top of UDP
- Run 2 Draw instances with -props /yourlocation/udp.xml -state
- Draw something in both instances
- Start a partition by clicking on "Start discarding messages" in 1 instance
- Once the cluster has fallen apart, clear both instances and draw something again
- The make the partition disappear by clicking on "Stop discarding messages"
- The 2 members will merge, but drawing in 1 of them causes that member not to receive any updates

"probe.sh op=NAKACK.printDigestHistory" will show that the unresponsive member asks itself for retransmission and it doesn't deliver its own messages

> NAKACK: overwriteDigest() doesn't adjust sequence number
> --------------------------------------------------------
>
>                 Key: JGRP-1251
>                 URL: https://jira.jboss.org/browse/JGRP-1251
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 2.10.2, 2.12
>
>
> NAKACK.overwriteDigest() is used by the 2 state transfer protocols (STATE_TRANSFER and STREAMING_STATE_TRANSFER).
> When A has a digest A:250,B:10,C:160, and gets the state (as a result of calling JChannel.getState() with a digest of A:230,B:10,C:160, it'll set its own digest to A:230 (from A:250). 
> However, A's sequence number (seqno) will remain at 250 ! This means, when A sends the next message, it'll send A:251, but because we set the digest to A:230, A will ask itself to retransmit messages A:230-250 !
> SOLUTION: when receiving digest A:230, A should set its seqno to 230
> WORKAROUND: use FLUSH, which doesn't ship digests on state transfer

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