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From nathanwray <nw...@detroitsci.com>
Subject Performance issue with Oracle backed AMQ
Date Thu, 01 Feb 2018 17:00:16 GMT
We recently had over 1M messages back up in a container.

For reasons that aren't completely clear, AMQ executed the query found in
Statements.getFindNextMessagesStatement mid-morning:

SELECT ID, MSG
    FROM activemq.ACTIVEMQ_MSGS
   WHERE CONTAINER = :1 AND ID > :2 AND ID < :3 AND XID IS NULL
ORDER BY ID;

With the parameters:
1              queue://generic_createContract
2              -1
3              183893253

This call appears to originate from
DefaultJDBCAdapter.doRecoverNextMessages, which calls setMaxRows on the
PreparedStatement with (apparently) 200 rows.  

However it appears the Oracle thin driver makes no attempt to limit the
result set based on the max rows value; instead it selects and sorts the
entire 1M row plus values and makes them available to the client, which
stops creating objects after reading the first 200.

The net result was that our Oracle server spiked to 90%+ on this one query
and caused a complete AMQ failure in production, knocking over a number of
critical systems.

We wound up stopping all of our brokers and manually dropping the messages
in this container in order to resolve the 3 hour outage.

Is there a known issue with using Oracle persistence with AMQ that precludes
having more than thousands of messages?  If the "max rows" approach with the
thin driver works as it appears to, we can't be the first to have seen this
problem.

Any insight would be appreciated.

Thank you
Nathan





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