[jboss-jira] [JBoss JIRA] (JGRP-1875) UNICAST3/UNICAST2: sync receiver table with sender table

[Bela Ban (JIRA)]

Bela Ban created JGRP-1875:
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             Summary: UNICAST3/UNICAST2: sync receiver table with sender table
                 Key: JGRP-1875
                 URL: https://issues.jboss.org/browse/JGRP-1875
             Project: JGroups
          Issue Type: Enhancement
      Security Level: Public (Everyone can see)
            Reporter: Bela Ban
            Assignee: Bela Ban
             Fix For: 3.5


If a receiver B closes its recv-table and the sender A doesn't, then (when receiving msgs from the sender) the receiver engages in a protocol using {{GET-FIRST-SEQNO}} to sync itself with the sender. This has several problems, detailed in JGRP-1873 and JGRP-1874. (Note that the other way round (sender closing send-table), there is no issue, as the sender will create a new connection with a new {{conn-id}}).
To prevent {{STABLE}} messages interfering with {{GET-FIRST-SEQNO}} messages (JGRP-1873), we could run an additional {{SYNC}} protocol round, e.g.
* B needs to get the lowest and highest seqno sent from A
* B sends a {{SYNC}} message to A (instead of a {{GET-FIRST-SEQNO}} message)
* B sets a flag that discards all {{STABLE}} messages on reception of {{SYNC}}
* B replies with a {{SYNC-OK}} containing the _lowest_ and _highest_ sent seqnos
* B creates an entry for A with the lowest and highest seqnos
* B sends a {{SYNC-DONE}} to A
* A resets the flag and starts accepting {{STABLE}} messages from B again
* A and B now use the usual protocols to retransmit missing messages





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