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https://issues.apache.org/jira/browse/FELIX-5394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15636472#comment-15636472
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Felix Meschberger commented on FELIX-5394:
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Apart from that, there is indeed a proplem with the plugin: The documentation
of the _Dump Threshold_ property states _zero to disable automatic dump
creation_.
This is clearly not implemented like that. Rather the implementation does this
when the property is zero:
* Registers the notification listener (yes, this listener is always
registered !)
* Sets the threshold to zero on all memory pools allowing to set the
threshold. This causes these pools to not send events.
Now, should some other system tooling decide to set the threshold to some value
(of course this setting is sort of a race condition between this plugin and the
other tool), the plugin will receive events and in contrast to the stated
"disable automatic dump creation", dumps will be created.
We should fix this as follows:
* Register the listener only in case a non-zero threshold is configured
* Make sure the listener is not registered (or unregistered) if a zero
threshold is configured
[~alex.parvulescu] Does that work for you ?
> Memoryusage plugin creates a heap dump on every notification
> ------------------------------------------------------------
>
> Key: FELIX-5394
> URL: https://issues.apache.org/jira/browse/FELIX-5394
> Project: Felix
> Issue Type: Bug
> Components: Web Console
> Affects Versions: webconsole-memoryusage-plugin-1.0.6
> Reporter: Alex Parvulescu
> Labels: patch-available
> Attachments: FELIX-5394-v0.patch
>
>
> As a part of OAK-4966 I'm trying to install a listener on available memory
> with a notification when a certain available memory threshold is met [0].
> This seems to clash a bit with the current {{memoryusage}} plugin, as both
> jmx listeners try to change the threshold for the notification, and
> subsequently both might receive the notification at a different value than
> expected. (for example I'm setting a notification at {{15%}} and even though
> the {{memoryusage}} plugin is not used and is currently set at {{0%}} it will
> still create a heap dump:
> {noformat}
> *WARN* [Service Thread] org.apache.felix.webconsole.plugins.memoryusage
> Received Memory Threshold Exceeded Notification, dumping Heap
> {noformat}
> I have 2 suggestions:
> * first is to _not_ change the threshold value if it's already set at a
> smaller value. this means the plugin will not break other listeners
> expectations of receiving an event
>
> * second is to verify the locally set threshold value against the values seen
> at notification time. this effectively means the plugin is free to ignore
> certain events, and not dump the heap to disk every time it gets a ping [1].
> I would like to provide a patch for this issue pretty soon as I really need
> to fix OAK-4966, unless someone is more eager to come up with a working
> solution.
> [0]
> https://issues.apache.org/jira/browse/OAK-4966?focusedCommentId=15629253&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15629253
> [1]
> https://github.com/apache/felix/blob/trunk/webconsole-plugins/memoryusage/src/main/java/org/apache/felix/webconsole/plugins/memoryusage/internal/MemoryUsageSupport.java#L553
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