[ http://issues.apache.org/jira/browse/JCR-245?page=all ]
Jukka Zitting updated JCR-245:
------------------------------
Attachment: TransientRepository.patch
The attached patch contains org.apache.jackrabbit.core.TransientRepository, a
proxy repository class that automatically initializes and shuts down the
underlying RepositoryImpl instance when sessions are opened or closed. I
implemented this as a separate class to avoid overloading the already heavy
RepositoryImpl class. The implementation is quite clean except for two things:
1) it loads the default repository descriptors directly from
repository.properties, and 2) it messes with
RepositoryImpl.loggedOut(SessionImpl) to avoid a nasty infinite loop in
RepositoryImpl.shutdown().
The class is quite easy to use and works very well with component containers
like Spring where setting up an explicit shutdown call is difficult and
cumbersome. If it weren't for the repository initialization and shutdown
overhead, it would also make a fine candidate for solving the deployment model
2 shutdown issues discussed lately on the mailing list. The implementation also
relies on all clients properly closing all the sessions they've opened. If
needed, the implementation could be modified to use a WeakHashMap to cope with
lost sessions.
Example code:
RepositoryConfig config = RepositoryConfig.create("...", "...");
Repository repository = new TransientRepository(config);
Session session = repository.login(); // Repository gets initialized
try {
// Use the session
} finally {
session.logout(); // Repository gets shut down
}
Any problems with this approach that I haven't noticed? I've been quite happy
using a class like this in my Spring-based projects, so unless anyone objects
I'll go ahead and commit it so others can use it too.
> Automatic repository shutdown
> -----------------------------
>
> Key: JCR-245
> URL: http://issues.apache.org/jira/browse/JCR-245
> Project: Jackrabbit
> Type: New Feature
> Components: core
> Reporter: Jukka Zitting
> Attachments: TransientRepository.patch
>
> Currently Jackrabbit relies on two mechanisms for safely shutting down a
> repository:
> 1) client application invoking RepositoryImpl.shutdown(), or
> 2) the shutdown hook installed by RepositoryImpl being run
> Both of these mechanisms have problems:
> 1) The shutdown() method is not a part of the JCR API, thus making the
> client application depend on a Jackrabbit-specific feature
> 2) In some cases the shutdown hook is not properly run (see issues
> JCR-120 and JCR-233)
> I think the JCR spec thinks of the Repository and Session interfaces as being
> somewhat similar to the JDBC DataSource and Connection interfaces. The
> Repository instances have no real lifecycle methods while the Session
> instances have clearly specified login and logout steps.
> (DataSource.getConnection() = Repository.login(), Session.logout() =
> Connection.close()) However the Jackrabbit implementation defines an explicit
> lifecycle for the RepositoryImpl instances.
> This causes problems especially for container environments (JNDI, Spring)
> where it is hard or even impossible to specify a shutdown mechanism for
> resource factories like the Repository instances. The current solution for
> such environments is to use a shutdown hook, but as reported this solution
> does not work perfectly in all cases.
> How about if we bound the RepositoryImpl lifecycle to the lifecycles of the
> instantiated Sessions. A RepositoryImpl instance could initialize (and lock)
> the repository when the first session is opened and automatically shut down
> when the last session has logged out. As long as the sessions are properly
> logged out (or finalized by the garbage collector) there would be no need for
> an explicitly RepositoryImpl.shutdown() call. The current behaviour of
> pre-initializing the repository and shutting down during a shutdown hook
> could be enabled with a configuration option for environments (like global
> JNDI resources) in which the shutdown hooks work well.
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