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From "Alex Parvulescu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FELIX-5394) Memoryusage plugin creates a heap dump on every notification
Date Fri, 04 Nov 2016 15:04:58 GMT

    [ https://issues.apache.org/jira/browse/FELIX-5394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15636598#comment-15636598

Alex Parvulescu commented on FELIX-5394:

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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