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From HellKnight <hellkni...@foxmail.com>
Subject Is it possible to dispatch a message in the topic to only a certain queues while using virtual topic?
Date Fri, 11 Oct 2013 02:51:17 GMT
I am using virtual topics but I've encountered a problem and I could not come
up with a perfect solution , so I decide to post it and I believe you guys
could help me .

My use case is something like this :
   a producer is monitoring a database.Once the database is updated, the
producer will send a message to anyone who is concerned about data updating
in that database, which means every message could be sent to one or more
consumers.However, don't assume that different messages will be sent to same
consumer groups.
    I am using virtual topics ,so the producer just sends message to a topic
called "VirtualTopic.AlertTopic". And as I have mentioned , there are
multiple users in my system just like ActiveMQ forum. Every user could run a
client program and login to the system , and the client program includes a
consumer to receive messages.  Messages sent to the virtual topic will be
dispatched to every queue, which means every message is actually sent to
every consumer, I have to use a message selector in the consumer side to
filter messages.
   I have created a queue named as "Consumer.UserID.VirtualTopic.AlertTopic"
for every system user. However, users will be add and removed dynamicly ,
and I should create a queue when adding a user and removing that queue when
removing the user from my system. If add a queue to ActiveMQ broker failed
due to exceptions, network failures etc.Then the user himself will find that
no message is received and he will just tell me ,so that is not a serious
problem.  
     However, if removing the user queue from activemq broker failed , there
will be some trouble. The user queue still exists, and since every message
sent to a virtual topic will be copied to every consumer queue , messages
will accumulating in the  queue that should be removed because the system
user who will consume that queue is removed from system managing database
and will never login again.  
     I've come up with two solutions:
1. Delete any user queue that has no active consumer for a long time , say ,
3 months. But this is imperfect, because it's possible that system user
would not login for months in our system , we consider that a normal
behaviour.

2. Purge a queue when it reach storage limits. This is good ,after all the
user won't like too many messages appear on his screen after a long offline
time.However, some users may hate this behaviour , they don't wonna miss any
notification messages

   I think there is an ideal way to deal with my problem. The message should
only be dispatched to the queues of its receivers, not all the queues. Is it
possible to do that?
 
    



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