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https://issues.apache.org/jira/browse/FELIX-5394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15636598#comment-15636598
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Alex Parvulescu commented on FELIX-5394:
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very reasonable proposal, thanks for looking into this [~fmeschbe]!
could you just clarify who will be responsible for setting the threshold on the
memory pool? will the plugin not set it any more going forward?
also, might I add a small thing to your list: if the plugin is registered for a
specific threshold and it receives an event, it should check that the memory
delta is within that threshold before creating the dump. this safeguards
against receiving events because from some external tool changed the threshold
in the mean time. all the need memory-related info is in the event itself, so
performing this check is not too intrusive (example from oak [0]).
[0]
https://github.com/apache/jackrabbit-oak/blob/trunk/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/GCMemoryBarrier.java#L162
> 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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