[jira] [Reopened] (AMQ-4467) Memory usage percent can be exceeded much if PFC is disabled

["Gary Tully (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AMQ-4467?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gary Tully reopened AMQ-4467:
-----------------------------
      Assignee: Gary Tully  (was: Dejan Bosanac)

The fix applies the cursor high water mark value to the shared system usage limit in error.
When checking if the shared or parent system usage is exhausted a value of 100% should be used while the per destination limit can be validated against the memoryUsageHighWaterMark via the perDestination percentUsage.

This becomes apparent with low values for memoryUsageHighWaterMark. With N destinations, the shared system usage can easily exceed this low per destination value and starve dispatch/pageIn for subsequent destinations.


> Memory usage percent can be exceeded much if PFC is disabled
> ------------------------------------------------------------
>
>                 Key: AMQ-4467
>                 URL: https://issues.apache.org/jira/browse/AMQ-4467
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.x
>            Reporter: SuoNayi
>            Assignee: Gary Tully
>             Fix For: 5.9.0
>
>         Attachments: AMQ-4467.patch
>
>
> If PFC is disabled, when the store cursor checks limits, it checks only the memory percentage of its own MemoryUsage and compares it to the high water mark. Otherwise if PFC is enabled, it checks whether the MemoryUsage is "full" but the "isFull" method also checks its parents.
> This issue arrises when you have memory limits set on queues higher than the overall system limit, as well as if you have multiple queues who's memory limits combined are higher than the overall system limit. These settings must be taken into account.
> The original form can be found at 
> http://activemq.2283324.n4.nabble.com/What-can-be-reason-of-460-memory-usage-limit-td4665651.html



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