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From magellings <>
Subject Re: duplicates on master/slave broker failover
Date Fri, 25 Sep 2009 20:57:34 GMT

Evaluating this further it appears the broker is not persisting any
information back to the database when it dispatches messages to consumers. 
I verified by removing update privs on the ACTIVEMQ_MSGS table as well as
insert, update, and delete privs on the ACTIVEMQ_ACKS table.  Yes we are
using JDBC Master/Slave.  It seems that if this is the case the master
broker must be tracking dispatches of messages to consumers in memory.  So
it would be impossible for a new master broker to know if a consumer had
received a message.  Does this seem correct to anyone more knowledgeable on
how JDBC Master/Slave works?  Also, what is the ACTIVEMQ_ACKS table for?  It
almost seems like this table would be used to keep track of the acks a
consumer sent back to a broker or something and possible would be used to
resolve the possiblity of a duplicate message being dispatched to another
consumer when a slave became master.  Except like I said after revoking
insert, delete, update privs on this table the broker continues to work just
fine.  So it doesn't look like the table is utilized.  

Any help is appreciated.  Thanks
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