NAKACK2: message batching leads to duplicate OOB messages --------------------------------------------------------- Key: JGRP-1593 URL: https://issues.jboss.org/browse/JGRP-1593 Project: JGroups Issue Type: Feature Request Reporter: Bela Ban Assignee: Bela Ban Fix For: 3.3 In NAKACK2.up(MessageBatch batch): * Assume we have a batch of 5 copies (duplicates) of message A5 * When we call Table.add(List), it returns true if at least one message was added ** Say the first A5 message was added, but the others were discarded * If the message is OOB, then for each message, we ** Check if we can set OOB_DELIVERED ** If true, we pass it up, else we discard it * However, because every A5 message is a *copy*, we'll be able to set the flag on *all* 5 messages and pass all messages up ! * This means we're allowing the 4 duplicate messages to pass up ! Note that this does *not* happen when we don't batch messages as every messages is added individually, and 'added' will therefore be true or false. Also, if we're the sender of a message (loopback), then we'll fetch, for each seqno, the corresponding message from the table and therefore setTransientFlagIfAbsent() will only return true *once* for the same message, as we're fetching the same message for the same seqno. SOLUTION: * Add another Table.add(List) method which *removes* all messages that weren't added to the table from the list(because they were dupes) ** This method would only get called if the message batch is OOB * If OOB and at least 1 message was added, we can now pass all messages from the remaining list up and set OOB_DELIVERED ** As the messages in the list have been added to the table (keyed by seqno), if some other thread wants to add a message with the same seqno, it'll fail as OOB_DELIVERED is already set and we're dealing with the same message