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From Rob Davies <>
Subject Re: active mq (size of the internal data structure and expiration of messages)
Date Wed, 07 Feb 2007 20:21:44 GMT

On 7 Feb 2007, at 19:38, Suchitha Koneru ((sukoneru)) wrote:

> Hello Active Mq Users ,
>                       I am using Publish/subscribe model for  
> transfer of
> messages with durable subscriptions. I suppose that active mq
> internally stores messages using queue or a similar data structure.
yes it does. For Durable Subscribers,  there is one queue for the  
messages, and for each subscriber a queue of references, one  
reference, per message for each subscriber. When there are no more  
interested subscribers in the message, it will be removed from the  
message queue.
> I was just wondering about the size of this queue maintained  
> internally
> by Active MQ. Does it  overflow ? How will we know, what it's capacity
> is ?
> Any insight in regard to this ?
We support a lot of different storage options, and although we expose  
the depth (cardinality) of the queue, as yet, we do not provide a  
generic mechansim for imposing limits on the durable messages.
> Also , the messages place in this internal queue  will be   
> discarded  ,
> once they expire ?  What is the time frame , within which they have to
> be consumed ? is there a way to determine this?
Messages are generally discarded when they expire. Some storage  
options only do this when fetching the messages (check to see if the  
message should be expired) - others do it periodically (this will  
become the norm for all message stores).


Rob Davies

> thanks,
> Suchitha

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