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https://issues.apache.org/jira/browse/AMQ-5716?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michal Kubricht updated AMQ-5716:
---------------------------------
Attachment: TopicSubscriptionTest.java
junit_amq_5716.patch
fix_amq_5716.patch
> TopicSubscription gets into endless loop when memory limit reached
> ------------------------------------------------------------------
>
> Key: AMQ-5716
> URL: https://issues.apache.org/jira/browse/AMQ-5716
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker
> Affects Versions: 5.7.0
> Environment: JDK-1.6.0_38
> Reporter: Michal Kubricht
> Attachments: TopicSubscriptionTest.java, fix_amq_5716.patch,
> junit_amq_5716.patch
>
>
> I might be wrong, but I think that there is a mistake in
> {{FilePendingMessageCursor}} in method {{isFull}}.
> The logic implemented in code is:
> -- isFull returns true when any of "memory usage is full" or "temp usage is
> full".
> From my point of view this is a mistake and logic should be:
> -- isFull returns true only when both of "memory usage" and "temp usage" are
> full.
> The reason why should this be fixed lies in the impact that this mistake
> caused us in our project:
> TopicSubscription got into endless loop in method {{add(MessageReference)}}
> when sending message into topic and memory limit reached 100% (it passed 100%
> in our case, but this is complete different story). Following conditions were
> fulfilled:
> * the dispatched queue reached consumer prefetch size,
> * producer flow control was disabled,
> * and finally related pending message cursor was full (because of memory
> usage).
> The temporary storage remained at 0%, it wasn't created at all.
> I understand what is the loop good for, it waits until there is a space in
> pending message cursor. This is a correct behavior. Anyway, when topic uses
> {{FilePendingMessageCursor}}, it loops for no good reason, because the cursor
> itself can handle the situation when memory limit is reached/full. It dumps
> all messages from memory list into disk list into temporary storage.
> I am providing a patch file for this fix and very basic JUnit test for it, if
> this is acknowledged as bug and its solution.
> Third file is a JUnit test is not considered to be part of commit (it never
> ends without any fix provided), but shows as simple as possible the topic
> subscription stuck scenario.
> If the cursor would return isFull as false, it would solve described
> situation. It is sure that I cannot know or even guess that this
> implementation of {{FilePendingMessageCursor}} is there for some other
> reason, so please take this only as my personal recommendation after some
> time spent on analysis of problem in our project.
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