[hibernate-dev] Re: Pushing indexes through JGroups

[Emmanuel Bernard]

Hello
I am not sure this is where we should go, or at least, it depends.  
here are three scenarii


#1 JMS replacement
If you want to use JGroups as a replacement for the JMS backend, then  
I think you should write a jgroups backend. Check  
org.hibernate.search.backend.impl.jms
In this case all changes are sent via JGroups to a "master". The  
master could be voted by the cluster possibly dynamically but that's  
not necessary for the first version.

#2 apply indexing on all nodes
JGroups could send the work queue to all nodes and each node could  
apply the change.
for various reasons I am not fan of this solution as it creates  
overhead in CPU / memory usage and does nto scale very well from a  
theoretical PoV.

#3 Index copy
this is what you are describing, copying the index using JGroups  
instead of my file system approach. This might have merits esp as we  
could diminish network traffic using multicast but it also require to  
rethink the master / slave modus operandi.
Today the master copy on a regular basis a clean index to a shared  
directory
On a regular basis, the slave go and copy the clean index from the  
shared directory.
In your approach, the master would send changes to the slaves and  
slaves would have to apply them "right away" (on their passive version)

I think #1 is more interesting than #3, we probably should start with  
that. #3 might be interesting too, thoughts?

Emmanuel

PS: refactoring is a fact of life, so feel free to do so. Just don't  
break public contracts.

On  May 21, 2009, at 22:14, Łukasz Moreń wrote:

> Hi,
>
> I have few questions that concern using JGroups to copy index files.  
> I think to create sender(for master) and receiver(slave) directory  
> providers.
> Sender class mainly based on existing FSMasterDirectoryProvider,  
> first create local index copy and send later to slave nodes
> (or send without copying, but that may cause lower performance?).
> To avoid code redundancy it would be good to refactor a little  
> FSMasterDirectoryProvider class, so then I can use copying  
> functionality in new DirectoryProvider and add sending one; or  
> rather I should work around it?
>
> I do not understand completely how does the multithreading access to  
> index file work. Does FileChannel class assure that, when index is  
> copied and new Lucene works are pushed?
>
>
> I hope you had great holidays:)
>
> Lukas