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Ken Giusti commented on QPID-3079: ---------------------------------- It may no longer apply, given the work done by Alan on HA and the async store interface work, this may no longer be an issue. I'd defer to Alan Conway - I seem to recall this issue was raised in order to facilitate new HA. > message.accept command should be completed on a per-dequeue basis > ----------------------------------------------------------------- > > Key: QPID-3079 > URL: https://issues.apache.org/jira/browse/QPID-3079 > Project: Qpid > Issue Type: Bug > Components: C++ Broker > Affects Versions: 0.8, 0.9 > Reporter: Ken Giusti > Assignee: Ken Giusti > Fix For: Future > > Attachments: proposal.txt > > > ** Overview > Asynchronous completion means that command execution is initiated in one > thread > (a client connection thread) and completed in a different thread. > When the async store is loaded, message.transfer commands are > completed by a store thread that does the async write. > ** Issues with asynchronous completion code as of revision r1029686 > *** Not really asynchronous > IncompleteMessageList::process blocks the connection thread till all > outstanding async commands (messages) for the session are complete. > With the new cluster, this could deadlock since it is blocking a Poller > thread. > *** Race condition for message.transfer > > Sketch of the current code: > // Called in connection thread > PersistableMessage::enqueueAsync { ++counter; } > // Called in store thread once message is written. > PersistableMessage::enqueueComplete { if (--counter == 0) notifyCompleted(); } > The intent is that notify be called once per message, after the > message has been written to each queue it was routed to. > However of a message is routed to N queues, it's possible for > notifyCompleted to be called up to N times. The store thread could > call notifyCompleted for the first queue before the connection thread > has called enqueueAsync for the second queue, and so on. > *** No asynchronous completion for message.accept > We do not currently delay completion of message.accept until the > message is deleted from the async store. This could cause duplicate > delivery if the broker crashes after completing the message but > before it is removed from store. > There is code in PersistableMessage to maintain a counter for dequeues > analogous to to the async enqueue code but this is incorrect. > Completion of transfer is triggered when all enqueues for a message are > complete. > Completion of accept is triggered for *each* dequeue from a queue > independently. > Furthermore a single accept can reference many messages, so it can't be > associated with a message. > ** New requirements > The new cluster design will need to participate in async completion, e.g. > an accept cannot be comlpeted until the message is > - removed from store (if present) AND > - replicated to the cluster (if present) as dequeued > The new cluster also needs to asynchronously complete binding commands > (declare, bind, delete) when they are replicated to the cluster. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@qpid.apache.org For additional commands, e-mail: dev-h...@qpid.apache.org