glassfish_at_javadesktop.org wrote:
> What good are clusters using instances on different physical servers if the server that houses the DAS central repository goes down? Is the DAS central repository supposed to be running on multiple servers (or is this even possible)?
>
> Based on my limited understanding, if the DAS server goes down, the entire Glassfish configuration (domain) is down, including a cluster with instances running on different physical servers. What am I missing?
>
In a domain(group of nodeagents/clusters/instances), DAS(Domain
Administration Server) is a central component for controlling all your
clusters/instances. When a instance/cluster(logical group of instances)
starts up it gets all its associated applications/configuration to its
own local repository from the DAS by the way of synchronization. The
instance will use its local repository for running the instance.
Whenever a new config change or new applications deployed(you can do
this only using the DAS(using asadmin or adminGUI)) pertaining to a
instance, the instance gets notified and the new changes/applications
are synchronized to the instance.
Now when a DAS goes down , nothing will happen to the instances as it is
managed by the nodeagents. The instances will continue to run and serve
the users.
With DAS down and if a instance crashes it will be automatically
restarted by the nodeagent. When the instance restarts it will try to
sync up with the DAS, since DAS is down it will use the existing local
repository and starts up fine.
So DAS doesnot have to be highly available for the instances to function.
-Sankar
> Thanks
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