[mod_cluster-dev] [Fwd: mod-cluster and domains]

jean-frederic clere jclere at redhat.com
Sat Jul 18 02:54:08 EDT 2009

On 07/17/2009 06:54 PM, Paul Ferraro wrote:
> On Fri, 2009-07-17 at 16:51 +0200, Bela Ban wrote:
>> Resent as the mod-cluster list didn't receive it
>> -------- Original Message --------
>> Subject: 	mod-cluster and domains
>> Date: 	Fri, 17 Jul 2009 13:34:09 +0200
>> From: 	Bela Ban<bban at redhat.com>
>> To: 	mod cluster<mod_cluster-dev at lists.jboss.org>
>> I've got a few questions regarding the functionality of mod-cluster:
>> *#1 Does mod-cluster support domains with sticky sessions ?_
>> _*I recall discussing this on *this* mailing list, and IIRC Paul
>> confirmed that mod-cluster supports domains with sticky sessions. I
>> actually tried this out and t worked.
>> I just need a quick confirmation on this. For config details, I'll go
>> and re-read the archives.
> Yes.
>> *#2 Disabling an entire domain*
>> I want to disable not just 1 node in a domain, but all nodes in a given
>> domain. Is this possible ? If so, I'd assume this is done through
>> mod-cluster-manager ?
> This is not yet possible.

There is a JIRA for his one. (MODCLUSTER-50)

>> *#2a: How do I know when all sessions of all nodes of a given domain
>> have expired ?*
>> This is necessary to know when I can shut down all nodes of a given domain
> mod_manager reports the number of active sessions per node.  This logic
> isn't completely accurate - as it defines an "active" session as one
> that was accessed within the last 5 minutes.
> To get accurate active session counts from each server in a domain,
> you'll need to verify the activeSessions attribute of the individual
> jboss.web:type=Manager,* mbeans via jmx-console, or similar.
> The plan is to implement stop(...) management methods (i.e. for graceful
> shutdown) that disables the node, waits for all sessions to drain, then
> stops the node.
> We'll allow this per domain as well.

All that logic goes in the JAVA part.

>> *#3 Starting an entire domain in disabled mode*
>> I want to start all nodes, one by one, in a given domain as *disabled*
>> (all webapps). Is it sufficient to just start all nodes as disabled ? Is
>> it possible to start a node in disabled mode at all ?
> This is not possible, atm.

We should need a table (shared information) on the domain and for the 
moment the domain is just an information of the node.

>> *#4 Enabling an entire domain*
>> When all nodes in a domain have been started as disabled (step #3), I'd
>> like to tell the httpds to enable all (or a selected set of) webapps in
>> a given domain, in all nodes of that domain. Is this possible ?
> In general, we have not yet implemented per-domain management functionality.
> I'll create JIRAs for these.
>> The point behind these 4 questions is that I want to demo how to disable
>> a domain, shut it down, upgrade the HW/SW, start it again, and re-enable it.

It is "easy" to add a command in the mod_cluster-manager that disable 
all the nodes corresponding to a domain. The scenario of the demo would be:
1 - dissable domain x
2 - show that an existing session still uses the domain.
3 - show that a new session goes to another domain.
4 - stop the domain (HW/SW).
5 - show that an existing session give an error (sticky) or failover (if 
not sticky).
6 - start it again and show that it is re-enabled.
Does that fit your needs?



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