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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