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Date: Fri, 10 Nov 2006 00:31:43 +0000
From: Ian Boston <ieb@tfd.co.uk>
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To: dev@jackrabbit.apache.org
Subject: Re: New feature: Clustering
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Will it be possible to replace FileJournal with something more message 
oriented ?
eg JGroups or ActiveMQ (JMS Topic)

This is to make the cache invalidation a real event rather than a poll, 
and to make the propagation fast.

I believe that you can configure AMQ to manage the persistence of topics 
  in various ways so it may cover the outstanding issues you have with 
Journal management..... just a thought.

Ian


(BTW, thanks for you comments on what type of cluster... all makes sense 
and fits our situation (www.sakaiproject.org) )


Dominique Pfister wrote:
> Hi,
> 
> I just committed some files to implement a first approach to
> clustering in jackrabbit. Inside this approach, all repositories in
> the cluster share the persistence layer (e.g. a derby database started
> standalone). When a repository commits some changes, it will write a
> log record to a shared "journal" directory. Another repository
> watching that directory will eventually read this record, invalidate
> its internal caches and fire corresponding events.
> 
> In order to enable clustering on some repositories, do the following
> for each repository:
> 
> (1) Configure persistence managers with sharable data sources, e.g. 
> standalone
>     databases instead of embedded ones
> (2) Add a configuration entry to the end of your repository's 
> repository.xml:
> 
> <Cluster id="nodeX" >
>  <Journal class="org.apache.jackrabbit.core.cluster.FileJournal">
>    <param name="directory"  value="/mnt/journal"/>
>    <param name="revision" value="${rep.home}/repository/revision" />
>  </Journal>
> </Cluster>
> 
>    This will make the repository write changes to the directory
> "/mnt/journal" and read
>    changes made by others in the cluster. Make sure that every
> repository will get
>    a different value for the "id" attribute. Alternatively, you may
> set the system
>    property named "org.apache.jackrabbit.core.cluster.node_id" to
> your preferred
>    value.
> 
> Features still missing in the current implementation are:
> 
> - Automatic archival of journal log entries to save space
> - Using a database as backend for the journal
> - And probably a lot more...
> 
> The status of those features can be tracked here:
> 
> https://issues.apache.org/jira/browse/JCR-623
> 
> Kind regards
> Dominique Pfister