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From André Warnier ...@ice-sa.com>
Subject Re: TomcatCluster data replication
Date Wed, 06 Apr 2011 19:43:02 GMT
Jürgen Jakobitsch wrote:
> hi,
> 
> i'm in need of data replication in a tomcat-cluster.
> i set up a tomcat cluster of three tomcats on a single machine with a apache (mod_jk)
front that does the load balacing.
> everything works absolutely charming for reading requests, my trouble start with data
input.
> 
> what i'm trying to achieve is that if i submit data with a html form, the storage on
all cluster members needs to be updated.
> i'm using an openrdf's sesame triple store which locks it's data directory so i can't
simply use a single shared directory
> in my application.
> 
> what i have in mind, after first readings, is some sort of clustervalve that checks,
if a request is a POST request and if
> yes, sends this request (which updates the repository in the back) to all members of
the cluster.
> 
> so here would be my questions :
> 
> 1. is there a standard way of doing something like (which a not-clusterable data-backend)

No.

> 2. is the thing with the clustervalve in fact the correct starting point

Probably not.

> 
> any help or pointer to the right direction greatly appreciated
> 
I'm not saying that it would not be possible to do this.  And I have no idea what a 
"openrdf's sesame triple store" is.
But what you describe sounds more like something that should be handled at the level of 
the application which processes the POST.  It is the application which should arrange to 
update the nn back-end data stores at the same time.  Of course that introduces some 
interesting issues of locking and synchronisation, in case two quasi-simultaneous requests

handled by two separate tomcats try to update the same piece of data in each of the 
datastores.

Now just by curiosity, what is the real-world point of this setup, considering that your 3

tomcats are running on the same host ?
Why not have a single Tomcat with 3 times more resources, to handle all the requests ?

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