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From "Alan Conway (JIRA)" <qpid-...@incubator.apache.org>
Subject [jira] Commented: (QPID-2364) Management updates in timer create inconsistencies in a cluster.
Date Tue, 26 Jan 2010 22:20:34 GMT

    [ https://issues.apache.org/jira/browse/QPID-2364?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12805240#action_12805240

Alan Conway commented on QPID-2364:

Attached first cut at a patch to introduce an abstract "PeriodicTimer" that is implemented
differently in standalone and cluster mode. In standalone mode it just uses sys::Timer.
In cluster mode it uses sys::Timer to multicast a periodic-timer control, the actual task
is executed on delivery of that control in the cluster dispatch thread.

As it stands it does not work because ManagementAgent adds its timer task before the cluster
plug-in initializes, so it is added to the default PeriodicTimer, not the clusters PeriodicTimer.


> Management updates in timer create inconsistencies in a cluster.
> ----------------------------------------------------------------
>                 Key: QPID-2364
>                 URL: https://issues.apache.org/jira/browse/QPID-2364
>             Project: Qpid
>          Issue Type: Bug
>          Components: C++ Broker
>    Affects Versions: 0.6
>            Reporter: Alan Conway
>            Assignee: Alan Conway
> Management updates are triggered by a timer. They are not predictable for the
> cluster and so can cause cluster shut-downs and inconsistent message delivery.
> We have a hack in place that suppresses exceptions when the session receives
> completions for transfers not yet sent (which is the usual manifestation of the
> unpredictability). I.e. we have in essence disabled consistency checking for
> management sessions. This solved immediate problems but would quickly stop
> working if sessions/connections could be used for management and other things
> (as will be more likely with QMFv2 where using management becomes quite
> straightforward).    
> In a cluster, management updates need to be synchronized by executing them in the cluster
dispatch thread rather than a timer thread.

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