UNICAST3/UNICAST2: sync receiver table with sender table -------------------------------------------------------- Key: JGRP-1875 URL: https://issues.jboss.org/browse/JGRP-1875 Project: JGroups Issue Type: Enhancement Reporter: Bela Ban Assignee: Bela Ban Fix For: 3.5.1, 3.6 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}} or {{ACK}} 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-ACK}} to A * A resets the flag and starts accepting {{STABLE}} / {{ACK}} messages from B again * A and B now use the usual protocols to retransmit missing messages