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https://issues.apache.org/jira/browse/CAMEL-5683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13470385#comment-13470385
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Raul Kripalani commented on CAMEL-5683:
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Beware that the LRU and the cleanup of the SoftReferences kick in at different
times. They cater for different situations:
- LRU logic is valuable when your recipientList can generate many, many
different producers. In a hypothetical case, if there are 2000 users and each
user has a dedicated JMS topic where you want to publish messages to from your
Camel route, you may end up with 2000 items in the ProducerCache, even if 1000
users are no longer active. The LRU allows Camel to vacuum potentially
irrelevant producers. There is a max. producer cache size you can set to
control the threshold.
- SoftReferences are valuable in near-OOM situations. It allows the JVM to
'intelligently' dispose of objects that can be recreated later, once the memory
exhaustion subsides.
Both functionalities are thus valuable. We just need to address the memory leak
in SoftReferences perhaps by using finalize().
> JMS connection leak with request/reply producer on temporary queues
> -------------------------------------------------------------------
>
> Key: CAMEL-5683
> URL: https://issues.apache.org/jira/browse/CAMEL-5683
> Project: Camel
> Issue Type: Bug
> Components: camel-jms
> Affects Versions: 2.10.0
> Environment: Apache Camel 2.10.0
> ActiveMQ 5.6.0
> Spring 3.2.1.RELEASE
> Java 1.6.0_27
> SunOS HOST 5.10 Generic_144488-09 sun4v sparc SUNW,SPARC-Enterprise-T5220
> Reporter: Michael Pilone
> Assignee: Claus Ibsen
> Fix For: 2.9.4, 2.11.0, 2.10.2
>
> Attachments: CamelConnectionLeak-ProducerTemplate.zip,
> CamelConnectionLeak.zip, Consumer List.txt, MAT Snapshot.png, Route
> Configuration.txt
>
>
> Over time I see the number of temporary queues in ActiveMQ slowly climb.
> Using JMX information and memory dumps in MAT, I believe the cause is a
> connection leak in Apache Camel.
> My environment contains 2 ActiveMQ brokers in a network of brokers
> configuration. There are about 15 separate applications which use Apache
> Camel to connect to the broker using the ActiveMQ/JMS component. The various
> applications have different load profiles and route configurations.
> In the more active client applications, I found that ActiveMQ was listing
> 300+ consumers when, based on my configuration, I would expect no more than
> 75. The vast majority of the consumers are sitting on a temporary queue. Over
> time, the 300 number increments by one or two over about a 4 hour period.
> I did a memory dump on one of the more active client applications and found
> about 275 DefaultMessageListenerContainers. Using MAT, I can see that some of
> the containers are referenced by JmsProducers in the ProducerCache; however I
> can also see a large number of listener containers that are no longer being
> referenced at all. I was also able to match up a soft-references
> producer/listener endpoint with an unreferenced listener which means a second
> producer was created at some point.
> Looking through the ProducerCache code, it looks like the LRU cache uses
> soft-references to producers, in my case a JmsProducer. This seems
> problematic for two reasons:
> - If memory gets constrained and the GC cleans up a producer, it is never
> properly stopped.
> - If the cache gets full and the map removes the LRU producer, it is never
> properly stopped.
> What I believe is happening, is that my application is sending a few
> request/reply messages to a JmsProducer. The producer creates a
> TemporaryReplyManager which creates a DefaultMessageListenerContainer. At
> some point, the JmsProducer is claimed by the GC (either via the
> soft-reference or because the cache is full) and the reply manager is never
> stopped. This causes the listener container to continue to listen on the
> temporary queue, consuming local resources and more importantly, consuming
> resources on the JMS broker.
> I haven't had a chance to write an application to reproduce this behavior,
> but I will attach one of my route configurations and a screenshot of the MAT
> analysis looking at DefaultMessageListenerContainers. If needed, I could
> provide the entire memory dump for analysis (although I rather not post it
> publicly). The leak depends on memory usage or producer count in the client
> application because the ProducerCache must have some churn. Like I said, in
> our production system we see about 12 temporary queues abandoned per client
> per day.
> Unless I'm missing something, it looks like the producer cache would need to
> be much smarter to support stopping a producer when the soft-reference is
> reclaimed or a member of the cache is ejected from the LRU list.
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