[jboss-as7-dev] Getting on the same page with @Clustered @Singleton

[David M. Lloyd]

Here's a brief summary of what we've decided so far on this.  We've 
determined that a @Clustered @Singleton would, if implemented, act 
similarly to a @Clustered @Stateful which only has one session.

When it comes down to spec, any kind of clustering is really non-spec 
behavior.  Having such features doesn't mean we aren't spec-conformant, 
it just means we have additional functionality which goes beyond 
specification.

Since we don't have @Clustered @Singleton today, this isn't considered a 
high priority for the next release.  But I suspect we could deliver this 
for 7.2 if we wanted to.

On 12/07/2011 12:15 PM, Andrig Miller wrote:
> The other complication, is that you may have a Singleton that has no state to replicate.  In that case, the single instance, with no replication makes sense.
>
> Andy
>
> ----- Original Message -----
>> From: "Radoslav Husar"<rhusar at redhat.com>
>> To: jboss-as7-dev at lists.jboss.org, "David Lloyd"<dlloyd at redhat.com>, "Paul Ferraro"<pferraro at redhat.com>
>> Sent: Wednesday, December 7, 2011 10:50:35 AM
>> Subject: [jboss-as7-dev] Getting on the same page with @Clustered @Singleton
>>
>> Hi guys,
>>
>> I just want to sync up with everyone what's the plan on EE6's
>> @Singleton
>> running on multiple JVMs in 7.1*.
>>
>> There is a common misconception that @Singleton is acting at cluster
>> level. This is nay. The EE spec says:
>>
>> A Singleton session bean is a session bean component that is
>> instantiated once per application. In cases where the container is
>> distributed over many virtual machines, each application will have
>> one
>> bean instance of the Singleton *for each JVM*.
>>
>>
>> However the concept of @Clustered @Singleton where there is only 1
>> failure-resistant bean instance within the cluster replicating state
>> does make a lot of sense. Having to sync on the persistence level
>> sounds
>> dreadful. In one sense it is the successor of AS 5's singleton-ha
>> which
>> was deployment-level mechanism.
>>
>> Is is possible to have this even though it is kind of violating the
>> EE spec?
>>
>>
>> David is requesting to fail the deployment of such:
>> https://issues.jboss.org/browse/AS7-2887
>>
>> Does it mean that we wont have it in 7.1? Maybe later?
>>
>>
>> Cheers,
>> Rado
>>
>>
>> * EAP 6.0
>> --
>> Radoslav Husar
>>
>> JBoss QE
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>> https://lists.jboss.org/mailman/listinfo/jboss-as7-dev
>>


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