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From "Marcos Sanz (JIRA)" <j...@apache.org>
Subject [jira] Created: (AMQ-1244) DatabaseLocker implementation impedes database replication
Date Fri, 11 May 2007 06:33:35 GMT
DatabaseLocker implementation impedes database replication
----------------------------------------------------------

                 Key: AMQ-1244
                 URL: https://issues.apache.org/activemq/browse/AMQ-1244
             Project: ActiveMQ
          Issue Type: Bug
          Components: Message Store
    Affects Versions: 4.1.1
         Environment: Latest ActiveMQ snapshot, Sybase ASE 12.5.x
            Reporter: Marcos Sanz
            Priority: Critical


The current implementation of the JDBC Master/Slave feature makes one broker (the master)
acquire a lock on a database object. In Sybase, this has been implemented with the command:

LOCK TABLE foo IN EXCLUSIVE MODE

This command can only be executed within a transaction, see:
http://manuals.sybase.com/onlinebooks/group-as/asg1250e/sqlug/@Generic__BookTextView/54552;pt=54651

This implies that for the whole lifespan of the ActiveMQ-process there is an open transaction
in the RDBMS. This is a problem in a professional environment making use of a database replication
server: The open transaction impedes that the transaction log in the active database is emptied,
then the stable queue at the replication server won't be purged and will steadily grow up
to infinitum. We have been able to observe this behaviour.

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