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From "John Heitmann (JIRA)" <>
Subject [jira] Commented: (AMQ-932) Quickly broken client connections lead to memory leaks
Date Sun, 24 Sep 2006 07:50:23 GMT
    [ ] 
John Heitmann commented on AMQ-932:

Those are the exact symptoms that occur as a result of the problem I saw. For every bad connection
there was a bunch of individual object leakage (one each of the major transport filters, a
couple different mbeans, a connection object etc), but by far the most serious leakage were
the empty pre-allocated marshaler cache arrays. This looks like a common symptom of anything
that would leak transports/connections, so it might not be the same root cause.

If you can reproduce it and want help I'd be happy to take a look.

If you can't find the problem one thing that could really help mitigate the severity of these
kinds of leaks is to make the initialization of the marshaling caches conditional on the wireFormat.cacheEnabled
flag. This would give a lot more leak headroom.

> Quickly broken client connections lead to memory leaks
> ------------------------------------------------------
>                 Key: AMQ-932
>                 URL:
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 4.0.2
>            Reporter: John Heitmann
>         Attachments: 73.diff
> Connections to the openwire port that are pathologically broken (for example any http
request) or that die in some other way extremely quickly will lead to memory losses of aout
64Kb each time. This happens because many services are stop()ed directly in the middle of
start(), and then never stopped for real, or stopped again but on an object tree with an inconsistent
state. This is usually also accompanied by the JMX message:
> WARN  ManagedTransportConnection     - Failed to unregister mbean: org.apache.activemq:BrokerName=localhost,Type=Connection,ConnectorName=default,Connection=25
> But that is a cosmetic symptom and not critical (and this has otherwise nothing to do
with JMX).
> My patch is a band-aid that is functional but I'm not very happy with it. The patch changes
some service logic so that if stop is called in the middle of start, the stop is instead queued
and called at the end of start. There will still be multiple stops, and you'll still see the
cosmetic JMX error from the second ineffectual stop, but the first stop cleans up correctly
so there are no leaks.
> I think there's probably a better solution, but it was tough to see what. I'd appreciate
better ideas. Possibly something involving moving the dangerous operations (wire format negotiation
etc) out of start?
> I am working on a unit test, but I can't promise I will have something to submit. I'm
having to play JVM games to detect the problem in a unit test and that might not fly for general
purpose use.

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