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From Jim_Cross <>
Subject Re: Memory Usage With No Subcribers and No Messages
Date Tue, 19 Jun 2007 12:07:28 GMT

Hi Saqib,

Thanks for your reply.
Unfortunately we're only using a single non-durable topic - no queues and no
durable topics.

Looking at the MBean for the topic after about an hour I see:
DequeueCount: 472089
DispatchCount: 472225
EnqueueCount: 24139

Does this sound normal? And do you know whether there's any documentation
relating to the attributes exposed by the MBeans?

srasul wrote:
> Hi,
> I am no activeMQ expert... but... this might be the "fast-producer &
> slow-consumer" issue. If you use Queues, and there is fast producer and a
> slow consumer, you will eventually run out of memory.
> this is because JMS has guaranteed message delivery. meaning any message
> you send must be delivered, one way or another. So the message is
> persisted in memory until someone comes along and consumes it. this could
> be why you are running out of memory. you can see this in JConsole's JMX
> beans. check out how many messages were put into a queue and how many were
> popped off it.
> i guess the solution might be to:
> - have messages that have short lifespan and are removed after a while if
> no one consumes it. this may fix the issue, but could also just delay when
> you run out memory
> - use non-durable topics rather than queues where is message is discarded
> if there is no-one around to consume it.
> regards,
> Saqib
> Jim_Cross wrote:
>> So I tried the recommendation in another thread:
>>     <memoryManager>
>>        <usageManager id="memory-manager" limit="1048576"/>
>>     </memoryManager>
>> And it ran with the 20 subscribers, 15 publishers, around 15 messages
>> every 2 seconds for just over an hour before again running out of memory
>> (see graph below).
>> This is a serious problem for us, as it seems memory usage never settles
>> down.
>> Jim_Cross wrote:
>>> Hi,
>>> I'm using ActiveMQ 4.1.1 on a Linux box, standard configuration plus a
>>> single additional topic.
>>> If I start ActiveMQ, and don't start any subscribers or producers (so no
>>> subscriptions and no messages sent to the topic), and take a look at
>>> JConsole, I see the attached memory usage - every minute heap usage goes
>>> from ~4mb up to ~13mb, then gets garbage collected back down to 4mb.
>>> Is this normal? 9mb seems like quite a lot of memory to be eating up
>>> over the course of a minute when there's no activity at all.
>>> The reason I started looking at this is that with approximately 20
>>> non-durable subscribers, plus 15 producers each sending around 1 message
>>> every couple of seconds, it runs fine for bout 20 mins, then hangs with
>>> 100% memory usage.
>>> I'm going to increase the available memory to the broker, to see whether
>>> it settles down at a max somewhere over 20mb.
>>> Any insight into why ActiveMQ uses so much memory when there's no
>>> activity, and whether there are any config changes I can make to alter
>>> this, gratefully received.
>>> Jim

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