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https://issues.apache.org/jira/browse/QPID-7387?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lorenz Quack resolved QPID-7387.
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Resolution: Fixed
> [Java Broker, AMQP 0-8..0-91] Correct handling of consumer credit
> -----------------------------------------------------------------
>
> Key: QPID-7387
> URL: https://issues.apache.org/jira/browse/QPID-7387
> Project: Qpid
> Issue Type: Bug
> Components: Java Broker
> Affects Versions: 0.32, qpid-java-6.0, qpid-java-6.1
> Reporter: Keith Wall
> Fix For: qpid-java-6.0.5, qpid-java-6.1
>
> Attachments: WIP_Prevent0-9CreditManagerGoingNegative.patch,
> WIP_Python0-91PrefetchTest.patch
>
>
> -The {{Pre0_10CreditManager}} mishandles message credit. In some
> circumstances allows message credit to fall beneath 0. Once this has
> occurred, messages cease to flow to all consumers associated with the session
> (messages appear stuck on the queue). Recreating the session (or connection)
> will allow messages to flow again.-
> -This problem was reproduced on a 0.32 derivative but it appears the same
> issue will affect newer releases too.-
> New analysis has shown that the client starvation on 0.32 was fixed by
> QPID-6797. The issue was that the ConsumerTarget_0_8#_entryReleaseListener
> StateChangeListener removed itself unconditionally even in the case where a
> different state change happend. This meant that the credit would not be
> restored leading to wrong accounting in {{Pre0_10CreditManager}}.
> Furthermore, the message credit potentially going negative in the case where
> the credit limit is lowered by a basic_qos is expected and acceptable
> behaviour because the client does still have the messages associated with
> that credit prefetched. After those prefetched messages are acknowledged the
> credit will become positive again.
> However there are credit account issues in {{Pre0_10CreditManager}}.
> * The Manager should keep track of the credit even if the limit is unlimited
> (i.e. 0) because at a later point the limit might change through a basic_qos
> at which point we need to know the accurate credit state
> * {{useCreditForMessage}} does not handle negative credit correctly.
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