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https://issues.apache.org/jira/browse/QPID-7775?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Keith Wall reassigned QPID-7775:
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Assignee: Keith Wall
> Flow to disk should consider the size of the resident messages in memory.
> -------------------------------------------------------------------------
>
> Key: QPID-7775
> URL: https://issues.apache.org/jira/browse/QPID-7775
> Project: Qpid
> Issue Type: Improvement
> Components: Java Broker
> Reporter: Keith Wall
> Assignee: Keith Wall
> Fix For: qpid-java-broker-7.0.0
>
>
> Our current algorithm for triggering flow to disk has some shortcomings.
> * the algorithm does not account for memory returned by flow to disk.
> The decision to flow a message a newly arriving message to disk
> considers only the queue's target size and queue's depth. Once a
> queue depth is over its target, all messages will go to disk even if
> all messages have actually been flowed to disk. The same is true
> after recovery: flow to disk will be enabled even though there are no
> messages in RAM.
> * the fact that a queue's target size is assigned by periodically by
> housekeeping means that the queues target size can be wrong for most
> of the time. This is very apparent if a queue is growing; you
> actually see *most* messages flowing to disk even when there is ample
> memory. The target size is periodically recomputed but only remains
> correct for an instant, the queue returns to the flow to disk state as
> more messages are added. We see this during perf test runs.
> We will change the MessageStore so that it tracks the size of the messages
> that are held resident in memory. The flow to disk algorithm will be
> change to by triggered when the resident memory exceeds the virtual host's
> target size.
> This work is likely to fully replace the recent work done on QPID-7770.
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