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From Alexander Klimetschek <aklim...@day.com>
Subject Re: Clustered Jackrabbit
Date Mon, 14 Jun 2010 21:11:16 GMT
On Mon, Jun 14, 2010 at 22:54, Ryan Hochstetler
<ryan.hochstetler@jetisre.com> wrote:
> First the question, then the background:
> Is it necessary to configure a <Journal> in the repository XML when one
> and only one node is accessing a JCR datastore which is typically used
> in a clustered configuration?

I don't understand: the purpose of a cluster is that multiple nodes
share the same repository. And if you have a cluster, you need the
journal. The journal is there to let all nodes know what the latest
jcr state is, so that it a) knows that the persistence manager that
actually does the clustering in some way needs to get the latest data
and most importantly b) can clear its internal caches properly.

BTW: I guess with "datastore" you mean the general concept of storing
Jackrabbit's data, not the specific Jackrabbit DataStore concept for
binaries, right?

>  Is the <Journal> necessary for absolute
> datastore coherency once the JCR has been configured in journaled mode,
> or is it only used to keep concurrent readers and writers synchronized
> with each other?

As noted above, it is necessary to keep all nodes in sync, regardless
whether they are practically read-only or write-only.


> We have a two-node jackrabbit cluster which hosts our application
> configuration data.  We use bundle.OraclePersistenceManager with
> Jackrabbit hitting a non-jta datasource in JBoss.  It works nicely.  We
> have a separate application which serves as a failsafe configuration
> editor, in case an administrator manages to corrupt the configuration
> and leave JBoss unbootable or crippled.  This separate application does
> not have the benefit of the database authentication code in JBoss
> (customer requirements specify that we can't put the password in the
> repository.xml).  We've worked around the issue with for the
> PersistenceManager, but I'd prefer not to have to go through the same
> steps for the DatabaseJournal.
> Will it corrupt the JCR database tables if the journal table is not
> updated when running the failsafe configuration editor?  There would be
> no other readers or writers at the time.  Once the configuration is
> repaired, the failsafe app is shut-down and the JBoss cluster would be
> started again.
> Thanks,
> Ryan Hochstetler
> Senior Software Engineer
> JET Enterprise Team
> Raytheon Company

Alexander Klimetschek

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