Hi Peter,
I was wondering if you had any thoughts on this post from Bryan on River
users?
Hope you don't mind me asking ;)
Best Regards,
Peter Firmstone.
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Hi Bryan,
Sorry that no one got back to you about this. I'm afraid that I don't
know the answer to your question, I've copied the dev list into this
email in case someone who monitors that list (but not this one) has
any ideas.
Best regards,
Tom
On Thu, Jan 12, 2012 at 2:29 PM, Bryan Thompson <br...@systap.com> wrote:
> Just to follow up on this thread myself. I modified the pattern to return a
> "thick" future rather than a proxy for the future. This caused the RMI call
> to wait on the server until the future was done and then sent back the
> outcome. This "fixed" the DGC memory/thread leak by reducing the number of
> exported proxies drammatically.
>
> In terms of best practices, is distributed DGC simply not useful for exported
> objects with short life spans? Can it only be used with proxies for
> relatively long lived services?
>
> Thanks,
> Bryan
>
>> -----Original Message-----
>> From: Bryan Thompson
>> Sent: Tuesday, January 03, 2012 12:06 PM
>> To: u...@river.apache.org
>> Subject: DGC threads issue
>>
>> Hello,
>>
>> Background:
>>
>> I am seeing what would appear to be one DGC thread allocated
>> per exported object. This is using River 2.2 and Sun JDK
>> 1.6.0_17. Relevant configuration parameters are below.
>>
>> I am observing problems with the DGC threads not being
>> retired on a timely basis. The exported objects are proxies
>> for Futures which are being executed on the service. The
>> code pattern is such that the proxied Future goes out of
>> lexical scope quite quickly. E.g.,
>> rmiCallReturningProxyForFuture().get().
>>
>> Under a modest load, a large number of such Futures are
>> exported which results in a large number of long lived DGC
>> threads. This turns into a problem for the JVM due to the
>> stack allocation per thread. Presumably this is not good for
>> other reasons as well (e.g., scheduling).
>>
>> I have tried to override the leaseValue and checkInterval
>> defaults per the configuration options below. I suspect that
>> the lease interval is somehow not being obeyed, which is
>> presumably a problem on my end. However, I can verify that
>> the configuration values are in fact showing up in
>> System.getProperties() for at least some of the JVMs involved
>> (the one which drives the workload and the one that I am
>> monitoring with the large number of DGC lease threads).
>>
>> Some questions:
>>
>> Is this one-thread-per-exported proxy the expected behavior
>> when DGC is requested for the exported object?
>>
>> The DGC lease checker threads appear to expire ~14 - 15
>> minutes after I terminate the process which was originating
>> the RMI requests. This is close the sum of the default
>> leaseValue (10m) and checkInterval (5m) parameters, but maybe
>> there is some other timeout which is controlling this? If
>> this is the sum of those parameters, why would the DGC lease
>> threads live until the sum of those values? I thought that
>> the lease would expire after the leaseValue (10m default).
>>
>> Can the issue I am observing be caused by a low heap pressure
>> on the JVM to which the RMI proxies were exported? If it
>> fails to GC those proxies, even though they are reachable,
>> could that cause DGC to continue to retain those proxies on
>> the JVM which exported them?
>>
>> Is there any way to configure DGC to use a thread pool or to
>> have the leases managed by a single thread?
>>
>> Is it possible that there is an interaction with the useNIO option?
>>
>> Relevant options that I am using include:
>>
>> -Dcom.sun.jini.jeri.tcp.useNIO=true
>> -Djava.rmi.dgc.leaseValue=30000
>> -Dsun.rmi.dgc.checkInterval=15000
>> -Dsun.rmi.transport.tcp.connectionPool=true
>>
>> Thanks in advance,
>> Bryan
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