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Posted to dev@qpid.apache.org by "Alan Conway (JIRA)" <qp...@incubator.apache.org> on 2009/11/25 21:54:39 UTC
[jira] Updated: (QPID-2220) Assisting manual recovery from a
complete persistent cluster crash.
[ https://issues.apache.org/jira/browse/QPID-2220?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Alan Conway updated QPID-2220:
------------------------------
Summary: Assisting manual recovery from a complete persistent cluster crash. (was: Assisign manual recovery from a complete persistent cluster crash.)
> Assisting manual recovery from a complete persistent cluster crash.
> -------------------------------------------------------------------
>
> Key: QPID-2220
> URL: https://issues.apache.org/jira/browse/QPID-2220
> Project: Qpid
> Issue Type: Improvement
> Components: C++ Broker
> Affects Versions: 0.5
> Reporter: Alan Conway
> Assignee: Alan Conway
>
> If every member of a persistent cluster crashes then manual intervention is required to identify which store is most up-to-date, so it can be used to recover. We need to provide tools to assist in this identification.
> The cluster can save a config-change counter with each config change (cluster membership change). In recovery, the broker with the highest config-change counter has the best store. However if the last brokers in the cluster crash so close together that none can record a config-change we need an additional decider.
> The store at http://qpidcomponents.org/download.html#persistence maintains a global Record Identifier (RID), a 64 bit value that is incremented for each enqueue and dequeue. If the cluster stores (config-change,RID) pairs then in recovery we can use actual-RID - RID at config-change as a tiebreaker.
> Proposed change to MessageStore API:
> /** Returns a monotonically increasing value reflecting the number of changes to the store.
> * The value can wrap-around to 0.
> * Stores need not implement this function, they can simply return 0.
> */
> uint64_t getChangeCounter();
> The default implementation just returns 0 and the cluster must fall back to relying on config-change counts.
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