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From Paul Gale <>
Subject Have you written a custom lease database locker?
Date Fri, 08 Mar 2013 05:13:40 GMT

Using: ActiveMQ 5.8.0 on RHEL 6.0

The documentation states that storage lockers are pluggable with regards to
persistence adapters. Taking it at its word I tried to combine the
lease-database-locker with the KahaDB persistence adapter. Fail. After
looking at the code for the lease-database-locker it's no wonder: it's
expecting a JDBCPersistenceAdapter as a parent.  Doh. Not that pluggable
after all.

So I have to come up with my own version of a lease-database-locker that
_will_ work with the KahaDBPersistenceAdapter. Why? Per the doc: NFSv4 is
required for failover to work reliably using KahaDB when using its default
storage locker. I'm restricted to using NFSv3 which is not going to work
with the default shared-file-locker. Therefore I need a hybrid approach:
Kaha for storage and a database for locking. Sounds easy enough, all I need
is a custom database lease locker. Or so I thought. However, after looking
it over it doesn't appear to be quite so straightforward given the somewhat
bazaar separation of responsibilities that exist given the actual
implementations of the respective persistence adapters and lockers. I've
made a few attempts at such a locker (the details of which I won't get into
here) but none of them worked.

Has anyone out there written a custom locker like this? If so, any guidance
would be much appreciated.

If no one has attempted this then I'll start getting into the specifics of
my attempts so far and others can chime in at that point.

Incidentally the XML schema indicates that the lease-database-locker tag is
a legitimate child tag for kahaDB. Why is that given that they cannot work
together out of the box?


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