jackrabbit-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Simon Gash" <Simon.G...@gossinteractive.com>
Subject RE: cluster and cache question
Date Mon, 04 Apr 2005 09:55:55 GMT
I see what you mean. Which layer to cache depends on the level of
clustering you want to use. For example, I might be using a cluster so
that I can increase the number of people accessing the repository in a
read-only fashion (anonymous users). However any users changing content
would use a session running directly on a specific node in the cluster. 

I know this may sound obvious but this would keep the solution simple.
I'm guessing here that the number of people actually changing content
will always be much smaller than those  just using it. This will of
course depend hugely on what type of application you are using the
repository for but does happen to fit my own usage particularly well :)

On the other hand the rest of you might want to access a session across
a cluster, I think that would significantly increase the complexity of
the design. I'm a fan of IOC (inversion of control) wouldn't the best
solution be a pluggable design so that the JackRabbit users can provide
their own particular brand (Tangsol, OS ...) ? Who could possibly be
against a pluggable design :)

Simon


-----Original Message-----
From: Serge Huber [mailto:shuber2@jahia.com] 
Sent: 04 April 2005 10:21
To: jackrabbit-dev@incubator.apache.org
Subject: Re: cluster and cache question


While I'm not a huge expert in clustering either, but I do have a little
bit of experience with it.

Basically, all caches must be able to communicate with other nodes in
order to guarantee a coherent system. That means that the
SharedItemStateManager must use a cache that can communicate with other
nodes of the cluster, otherwise you'll run into problems.

For example : on node 1 you remove a node that is cached on node 2. 
Unless the cache on node 2 is notified, you will be in an incoherent
state. I know this is basic clustering, so sorry if I'm stating the
obvious here :)

So the basic rule of thumb is : everywhere there is a cache/hashmap that
is used to keep objects a memory, there should be a way to substitute
this for a clustered-aware cache implementation.

Also, I have used OSCache for clustering implementations, and although
it is very good, I also think that it would be a shame to limit
Jackrabbit to just this implementation. For example, we might want to
let the door open for clustering commercial cache implementations such
as Tangosol (not affiliated, it's just an example :)). JCS (at Apache),
also has some support for clustering, and there are others out there.

In case other cluster communication systems are needed, it might be
interesting to evaluate JGroups
(http://www.jgroups.org/javagroupsnew/docs/index.html) or JMS. JGroups
is already integrated with Tomcat, JBoss and others.

Regards,
  Serge Huber.

ps : I'd be willing to help on this of course, as it is something I am
also very interested in.

Simon Gash wrote:

>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
>>>      
>>>
>level.
>  
>
>>>the sticking point is how to synchronize the multiple jackrabbit 
>>>instances in a cluster.
>>>
>>>      
>>>
>>Have you seen the oscache approach for clustering? it seems
>>    
>>
>interesting.
>
>i didn't know oscache before, it looks interesting. thanks for the 
>pointer.
>
>  
>
>>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
>>    
>>
>scenario.
>  
>
>>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 
>more.
>
>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.
>
>cheers
>stefan
>
>  
>
>>thanks
>>edgar
>>
>>    
>>
>
>This email contains proprietary information, some or all of which may
be legally privileged. It is for the intended recipient only. If an
addressing or transmission error has misdirected this email, please
notify the author by replying to this email. If you are not the intended
recipient you may not use, disclose, distribute, copy, print or rely on
this email. 
>
>Email transmission cannot be guaranteed to be secure or error free, as
information may be intercepted, corrupted, lost, destroyed, arrive late
or incomplete or contain viruses. This email and any files attached to
it have been checked with virus detection software before transmission.
You should nonetheless carry out your own virus check before opening any
attachment. GOSS Interactive Ltd accepts no liability for any loss or
damage that may be caused by software viruses.
>
>GOSS - Ranked 4th in the Deloitte Technology Fast 50 Awards 2004 and
88th in the Deloitte Technology Fast 500 EMEA.
>
>
>  
>


This email contains proprietary information, some or all of which may be legally privileged.
It is for the intended recipient only. If an addressing or transmission error has misdirected
this email, please notify the author by replying to this email. If you are not the intended
recipient you may not use, disclose, distribute, copy, print or rely on this email. 

Email transmission cannot be guaranteed to be secure or error free, as information may be
intercepted, corrupted, lost, destroyed, arrive late or incomplete or contain viruses. This
email and any files attached to it have been checked with virus detection software before
transmission. You should nonetheless carry out your own virus check before opening any attachment.
GOSS Interactive Ltd accepts no liability for any loss or damage that may be caused by software
viruses.

GOSS - Ranked 4th in the Deloitte Technology Fast 50 Awards 2004 and 88th in the Deloitte
Technology Fast 500 EMEA.


Mime
View raw message