Clustering questions

[Mitch Claborn]

I'm investigating to set up my first Tomcat cluster and have some questions.

1.  Using a SimpleTcpCluster, it looks like session information is
replicated to all members of the cluster.  If all members of the cluster
go down at once, is the session information lost?  Can a simple cluster
be combined with a Persistent Manager to save session information if all
members of the cluster go down at once?

2.  If I set up a SimpleTcpCluster, does that eliminate the need for the
load balancer to use "sticky" sessions?

3.  Is it possible to use a PersisentManager and a shared database to
"replicate" sessions through the database, eliminating the need for the
clustering stuff?  I've read some posts that indicate that the
PersistentManager writes sessions to the database at its discretion, not
immediately.

4.  Has anyone used nginx as a load balancer for tomcat?  Any feedback
on the wisdom of that?


Mitch


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[Filip Hanik - Dev Lists]

Mitch Claborn wrote:
> I'm investigating to set up my first Tomcat cluster and have some questions.
>
> 1.  Using a SimpleTcpCluster, it looks like session information is
> replicated to all members of the cluster.  If all members of the cluster
> go down at once, is the session information lost?  Can a simple cluster
> be combined with a Persistent Manager to save session information if all
> members of the cluster go down at once?
>  
Tomcat 6 has two session managers
DeltaManager - all to all replication
BackupManager - primary/backup strategy
All members going down at once, means you have problem beyond
replication, and replication or storing session data will not solve
anything for you :)
> 2.  If I set up a SimpleTcpCluster, does that eliminate the need for the
> load balancer to use "sticky" sessions?
>  
yes, but it is still recommended to use sticky sessions. Many reasons why.
> 3.  Is it possible to use a PersisentManager and a shared database to
> "replicate" sessions through the database, eliminating the need for the
> clustering stuff?  I've read some posts that indicate that the
> PersistentManager writes sessions to the database at its discretion, not
> immediately.
>  
It happens periodically on a background thread.
> 4.  Has anyone used nginx as a load balancer for tomcat?  Any feedback
> on the wisdom of that?
>  
You have several options, buying an appliance or using software.
If you want software, you can use haproxy, or the apache webserver
(httpd) with mod_proxy_balancer or mod_jk

Filip

>
> Mitch
>
>
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