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From "Simon Gash" <Simon.G...@gossinteractive.com>
Subject RE: cluster and cache question
Date Mon, 04 Apr 2005 09:00:54 GMT
Guess there's no reason why the rest of us JackRabbit fans can't chew
over a few design ideas around clustering ;)

I was thinking how the 'observer' pattern could be used. Each node of
the cluster could have its own JackRabbit repository. The
SharedItemState Manager for each node would register with other nodes in
the cluster. Whenever an item is changed this is simply broadcast to any
other repositories that are listening.

There would also need to be a way of dealing with Sessions, unless you
implement the 'sticky' session stuff (Session always returning to the
same node in the cluster). 

Anyone else got any ideas...

-----Original Message-----
From: Stefan Guggisberg [mailto:stefan.guggisberg@gmail.com] 
Sent: 03 April 2005 12:21
To: jackrabbit-dev@incubator.apache.org
Subject: Re: cluster and cache question

hi edgar,

> > regarding clustering:
> > clustering is a very interesting topic and we had quite a few 
> > discussions on how it could be supported in jackrabbit.
> is there an archive of this?

unfortunately not, those have been only verbal discussions during coffe
breaks so far.

>  > clustering can IMO not be
> > entirely delegated to the PM. it has to be tackled on a higher
> > the sticking point is how to synchronize the multiple jackrabbit 
> > instances in a cluster.
> >
> Have you seen the oscache approach for clustering? it seems

i didn't know oscache before, it looks interesting. thanks for the

> I'm just thinking out loud, Local and Shared ItemStateManagers could 
> favor composition over inheritance. The current ItemStateCache 
> implementation is a good fit for the first, and an oscache like 
> approach could be a good choice for the latter in a clustering
> Maybe this could be a deployment decision, with a "shared-cache" tag 
> in the config file that leaves to the deployer the cache strategy 
> selection for shared ItemStates.
> A pluggable cache for shared item states would also be useful for 
> network deployments with or without clustering. Those who chose a 
> rdbms backend would be able to to use a cache that relies also in the 
> local filesystem, and not only in mem.

as you might have noticed i am not a huge fan of 'pluggable' core
components ;) but i agree with you that tackling clustering on the
shared ItemState cache level would be certainly worth thinking about

but as i said, i think it's a bit too early to address something as
complex and advanced as clustering at this stage.

> Sorry for being such a pain, I'm becoming a jackrabbit fun and I'd 
> like to use it on any project I get involved.

great to hear that! ...and don't worry about being a pain ;) your
feedback and your suggestions, although we might not always be sharing
the same position, are very much appreciated.
at the very least it forces us to explain and justify design decisions
that we've taken. on the other hand it might also lead us to reconsider
certain designs.


> thanks
> edgar

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