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https://issues.apache.org/jira/browse/QPID-144?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rob Godfrey reassigned QPID-144:
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Assignee: (was: Rob Godfrey)
> Potential deadlocks during failover
> -----------------------------------
>
> Key: QPID-144
> URL: https://issues.apache.org/jira/browse/QPID-144
> Project: Qpid
> Issue Type: Bug
> Components: Java Client
> Reporter: Steven Shaw
>
> There's a certain need for "failover safety" in the implemenation of public
> client api methods. Any method that blocks for a response frame should be
> wrapped in a FailoverSupport. FailoverSupport automates the retrying after
> catching a FailoverException (a RuntimeException).
> Methods that block waiting for a response frame are now easier to identify
> because they all call AMQProtocolHandler.syncWrite() (SyncWrite in the .NET
> client)
> Currently the only methods employing FailoverSupport are
> AMQConnection.createSession, AMQSession.createConsumerImpl and
> createProducerImpl.
> AMQConnection.createSession has 3 calls to syncWrite so certainly needs to be
> wrapped in FailoverSupport. No problem there.
> AMQSession.createConsumerImpl/createProducerImpl neither call syncWrite.
> Unless there is some other important way in which they block, they don't
> really need to be wrapped in the FailoverSupport. It does no harm however.
> The following methods use syncWrite() but are not wrapped in a
> FailoverSupport:
> AMQSession's commit(), rollback(), close()
> AMQConnection.close() via AMQProtocolHandler.closeConnection()
> BasicMessageConsumer.close()
> These need to be protected/wrapped in a FailoverSupport. Note that commit()
> and rollback() are not currently protected by a lock on failoverMutex either.
> Perhaps StateManager.attainState is the only other method that blocks for "a
> response frame". In this case a series of response frames that result in the
> state changing. The only use of attainState is in
> AMQConnection.makeBrokerConnection. It would appear to need to be wrapped in
> a FailoverSupport as otherwise the FailoverException will escape. Since this
> is failing-over during connection some care may be required. Note that the
> makeBrokerConnection is used at 3 different sites.
> In addition sendAcknowledgement appear to need to lock the failoverMutex.
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