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From "Alan Conway (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (QPID-4348) HA Use independent sequence numbers for identifying messages.
Date Thu, 23 May 2013 15:29:21 GMT

     [ https://issues.apache.org/jira/browse/QPID-4348?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alan Conway updated QPID-4348:
------------------------------

    Description: 
Currently HA code uses queue sequence numbers to identify messasges.
This assumes that message sequence is identical on primary and backup.

Implementing new features (for example transactions) requires that we tolerate
ordering differences between primary and backups.

We introduces a new, queue-scoped HA sequence number managed by the HA plugin.
This is used to identify messages independently of queue sequence numbers.

Needs careful implementation to avoid bad performance effects.
- Avoid adding headers, use the same mechansim as we have now for sending HA seq. nos.
- Use an efficient index struct (e.g. dequeue) to map HA seq. to queue seq.

The benefits:
- required to support TX
- required for re-use of stored messages for catchup
- more robust - aovidb

  was:
Currently HA code uses queue sequence numbers to identify messasges.
This assumes that message sequence is identical on primary and backup.

Implementing new features (for example transactions) requires that we tolerate
ordering differences between primary and backups.

We introduces a new, queue-scoped HA sequence number managed by the HA plugin.
This is used to identify messages independently of queue sequence numbers.

Needs careful implementation to avoid bad performance effects.
- Avoid adding headers, use the same mechansim as we have now for sending HA seq. nos.
- Use an efficient index struct (e.g. dequeue) to map HA seq. to queue seq.

The benefits:
- required to support TX
- required for re-use of stored messages for catchup
- more robust - aovids implicit assumption of synchronization


    
> HA Use independent sequence numbers for identifying messages.
> -------------------------------------------------------------
>
>                 Key: QPID-4348
>                 URL: https://issues.apache.org/jira/browse/QPID-4348
>             Project: Qpid
>          Issue Type: Improvement
>          Components: C++ Clustering
>    Affects Versions: 0.18
>            Reporter: Alan Conway
>            Assignee: Alan Conway
>
> Currently HA code uses queue sequence numbers to identify messasges.
> This assumes that message sequence is identical on primary and backup.
> Implementing new features (for example transactions) requires that we tolerate
> ordering differences between primary and backups.
> We introduces a new, queue-scoped HA sequence number managed by the HA plugin.
> This is used to identify messages independently of queue sequence numbers.
> Needs careful implementation to avoid bad performance effects.
> - Avoid adding headers, use the same mechansim as we have now for sending HA seq. nos.
> - Use an efficient index struct (e.g. dequeue) to map HA seq. to queue seq.
> The benefits:
> - required to support TX
> - required for re-use of stored messages for catchup
> - more robust - aovidb

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