[jboss-jira] [JBoss JIRA] (JGRP-1593) NAKACK2: message batching leads to duplicate OOB messages

[Bela Ban (JIRA)]

     [ https://issues.jboss.org/browse/JGRP-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bela Ban updated JGRP-1593:
---------------------------

    Description: 
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




  was:
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 (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 amd we're dealing with the same message





    
> 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

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