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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 Thu, 03 Nov 2016 14:29:58 GMT

    [ https://issues.apache.org/jira/browse/FELIX-5394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15632875#comment-15632875

Alex Parvulescu commented on FELIX-5394:

Interestingly, as seen on OAK-4966, there are 2 types of low memory notifications: {{MEMORY_COLLECTION_THRESHOLD_EXCEEDED}}
and {{MEMORY_THRESHOLD_EXCEEDED}} and this plugins only listens to one of them (the latter).
it would probably make sense to add the other one too as it seems more relevant to an OOME-pending
situation (reflects available memory post-gc). Of course this is just an improvement idea,
but if there's interest I could create a dedicated issue to followup on.

> 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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