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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 updated QPID-7387:
-------------------------------
Description:
-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.
was:
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.
> [0-8..0-91] Mishandling of message credit allows consumers to starve
> --------------------------------------------------------------------
>
> 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-6.1
>
> 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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