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From Francois Guillemette <francois.guilleme...@trilliantinc.com>
Subject Re: Messages hang in Queue even when consumers are present after failover
Date Wed, 09 Apr 2008 15:25:17 GMT

Okay, I think I found the problem.

There is a race condition between the time the message is set with the
broker sequence number (RegionBroker.java in send method), and the time it
is actually put in the database (DefaultJDBCAdapter.java in doAddMessage
method). 

I have seen that sometimes message with higher sequence number are put in
database before a lower sequence number.  For example: 386 is put in the
database before 385. If it is happening when JDBCMessageStore is recovering
the next message (lastMessageId is 384), then 386 will be fetched and the
lastMessageId will change to be 386. 385 is then put in the db but never
retrieved (stopping and restarting the broker will allow to retrieve the
message because at start the lastMessageId is -1).

I have synchronized the code inside the RegionBroker.send, and I don't have
gaps anymore. This is a workaround for us since we don't process a lot of
message. But maybe a more elegant solution is to set the brokerSequenceId in
doAddMessage of JDBCAdapter (I may be wrong, I didn't check if the
brokerSequenceId is used elsewhere).

Is anyone can confirm that this is bug? Thanks

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