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From William Ribeiro <wribe...@tricode.nl>
Subject In deph Jackrabbit clustering question
Date Wed, 29 Sep 2010 08:32:50 GMT
Hello everybody,

I got a question about Clustering Jackrabbit (v 1.6.2). I'm trying to figure
out how the clustering schematics works. I got a custom in-memory database
that I integrated with Jackrabbit: I already got custom PersistenceManager
and FileSystem implementations plus some other required classes. They are
working fine since I got my test repositories running with all
functionality.

The new feature that I want to support is Clustering. I started implementing
my custom Journal class, extending from AbstractJournal, but there are some
points that I really don't get.

I start 2 repositories/cluster nodes in the same machine but with different
configurations. Each repo has it's own unique ID and I think they are
compliant to the configuration rules stated here (
http://wiki.apache.org/jackrabbit/Clustering) since both repos start without
any problems.

I try to add content to one of the repos like this:
========================== JAVA CODE =====================================
Workspace ws = session.getWorkspace();
List<String> prefixes =
Arrays.asList(ws.getNamespaceRegistry().getPrefixes());
  if( prefixes == null || !prefixes.contains("wiki")){
    ws.getNamespaceRegistry().registerNamespace("wiki","
http://www.barik.net/wiki/1.0");
  }

  Node rootNode = keepAliveSession.getRootNode();
  Node encyclopedia = null;
  if(!rootNode.hasNode("wiki:encyclopedia")){
    encyclopedia = rootNode.addNode("wiki:encyclopedia");
  }
  else{
    encyclopedia = rootNode.getNode("wiki:encyclopedia");
  }
========================== END OF JAVA CODE ===============================

At this point, even before saving the session, a new Record is created and
stored in the shared Journal thus creating a new Revision. On the
synchronization thread of the other repo, I can see it retrieves this new
Revision record(NamespaceRecord) from the Journal and it's
NamespaceRegistryImpl updates two files: ns_reg.properties and
ns_idx.properties. Both repos are now synced to the Journal (revision 1, at
this point).

In the same session I continue to add some more dummy content:
========================== JAVA CODE =====================================
for (int i = 0; i < iterations; i++) {
  Node p = encyclopedia.addNode("wiki:entry");
  p.setProperty("wiki:title", new StringValue("Rose " + i));
  p.setProperty("wiki:content", new StringValue("A rose is a flowering
shrub. " + i));
  p.setProperty(JcrConstants.JCR_LASTMODIFIED, System.currentTimeMillis());
}
session.save();
========================== END OF JAVA CODE ===============================
No this is where things starts to get fuzzy. First of all, the new nodes are
only "flushed" when the session is saved, what is not the case with the
Namespace. Okay, after the session is saved, the synchronization thread of
the other repo get's a ChangeLogRecord from the Journal with a bunch of
changes. The SharedItemStateManager comes into play and persists the new
changes ... or at least it was suppose to. I cannot track/find where it
actually does it! I really don't get anything more by this point. The
LockManagerImpl, SearchManager also consume the events but I don't know what
it does exactly.

Anyway ... I can't understand how this mechanism works. I need to find the
method that invokes the FileSystem  for persisting the new items found in
the Journal's records.

Can anybody give me a light on this issue? I just found this that might help
me: http://jackrabbit.apache.org/jackrabbit-architecture.html

Thanks a lot.
Cheers

-- 
Met vriendelijke groet,
Tricode Professional Services BV

William R. J. Ribeiro
Developer

T:   +31 (0)318 55 92 10
F:   +31 (0)318 65 09 09
E:   wribeiro@tricode.nl
W:  www.tricode.nl

De Schutterij 12, 3905 PL Veenendaal, The Netherlands | KVK 30183142

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