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From Mark Thomas <ma...@apache.org>
Subject Re: how to properly configure tomcat 7 cluster with BackupManager
Date Thu, 27 Oct 2011 14:38:43 GMT
On 27/10/2011 14:43, markt@apache.org wrote:
> "J├╝rgen Link" <juergen.link@googlemail.com> wrote:
> 
>> Hi all, I successfully did set up a tomcat cluster (3 nodes) with
>> session replication, using the standard DeltaManager.
>> 
>> In order to allow for more nodes, I'd like to switch to
>> BackupManager for primary-secondary replication on a dedicated
>> backup node. Unfortunately, the official documentation (and various
>> other sources out there) simply states "For larger clusters, to use
>> a primary-secondary session replication where the session will only
>> be stored at one backup server simply setup the BackupManager". I
>> therefore tried to replace DeltaManager in all node's three 
>> context.xml by BackupManager, but sessions still get replicated on
>> all three nodes. I also tried to configure only one node with
>> BackupManager, but it didn't help either.
>> 
>> I'm obviously missing something - can someone give a sketch of how
>> to configure the cluster correctly?
> 
> The backup manager doesn't work the way you think it does. Consider a
> four node cluster with nodes A, B, C & D. If node A has 30 primary
> sessions (more on that on a sec) then 10 of them will be backed up on
> node B, 10 on node C and 10 on node D. Sessions may be primary
> (currently being used), backup (full copy of the primary) or proxy
> (no data but knows which nodes are primary and backup). If a node
> isn't the primary or a backup it will be a proxy.

That should say "If a node isn't the primary or a backup node for a
session then it will be a proxy node."

Also, you can use the Manager app to view sessions and it will show you
primary, backup or proxy info.

> You have to use sticky sessions with the backup manager else the
> primary node for the session keeps changing and that creates a lot of
> traffic.
> 
> If the primary node fails, any other node can take over since they
> all have either a backup or the proxy info.
> 
> Mark
> 
> 
> 
> 
> 
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