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From Gary Tully <>
Subject Re: change strategy for determining failure of primary in JBDC-backed setup
Date Thu, 24 May 2012 11:15:09 GMT
You would need to write some code, but the locker implementation can
be easily overridden.
The interface is:

It acquires the lock in start which typically blocks till it can get a
lock and there are periodic calls to keepalive once the lock is

and it is set via xml config on the JDBCPersistenceAdapter via

A lease type strategy may make sense, where a read to determine if
there is an existing owner is followed by a poll when the lease is
expired or an update to start a new lease if none exists. The owner of
the lease needs to renew before it expires and that interval needs to
be configurable to allow timely reclamation.

In the event that the connection drops, if it is recreated before the
lease expires, the master/slave state is retained. If the lease has
expired, a master and slave will contend for the lock to be the new

In your setup, it is odd that the dropped connection does not cause
the lock keepAlive to fail and the broker to terminate. It should,
unless there are tcp level options that need to kick in to see the
half close. Or some connection pool config that can pick up on the
failure, there are some validate options on commons jdbc pool that
could help there.

This has cropped up before, in the case of a ha jdbc back end
(clusterd) and there is a drop in the connection while the cluster
fails over due to say routine maintenance.

Currently there is no good solution to this because the default locker
will terminate on the dropped connection. A lease will help here, but
when the lease expires there is still the problem of picking a new
master. Not sure there is an easy solution to that.

Hopefully the above will help, but start with determining why in your
current setup, the lock keepalive is not triggering for you when the
connection is dropped because that is a little odd. unless you have
= 0.

On 24 May 2012 11:45, Alex Hooper <> wrote:
> Hi,
> We are running activemq 5.5.1 in an active/passive failover configuration
> with JDBC Persistence to an Oracle backend. The default strategy for
> determining whether the current master has failed is for the secondary
> server to attempt to get a lock on the database table, waiting indefinitely
> for the lock to be granted.
> This is not working (at least in our context) as, after a relatively short
> time in operation (a handful of hours at most) the connection to Oracle is
> dropped. Activemq doesn't notice this, so the secondary sits there happily
> waiting for a lock it can now never get and, in the event of a failure,
> won't serve any clients as it is not a master.
> Is there some way to change the decision mechanism to, eg, a polling
> strategy? Or can anyone suggest another resolution to this problem?
> Alex.
> --
> Alex Hooper
> Operations Team Leader, BMJ Group, BMA House, London WC1H 9JR
> Tel: +44 (0) 20 7383 6049
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