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From Shailesh Potnis <potnis2...@yahoo.com>
Subject Re: Axis Clustering in OC4J Cluster
Date Fri, 29 Jan 2010 00:09:14 GMT
Hi Afkham:

Appreciate for the additional info.  I was pulled in other tasks and now have been assigned
to this one again.

I would like to ask a question related to a part of your input -- related to URL Repository:

Am I correct in assuming the by Axis2 URL Repository, you are referring to Axis2 central (remote)
repository?

If I deploy the Axis2 web application with embedded repository (not shared central remote
repository) what would be the limitations?

Also if I do use a remote central repository, would I be able to deploy new services in the
central repository without having to redeploy entire Axis2 web application?

If I do use a remote central repository, would I be able to redeploy existing services (Potentially
with modified implementation) in the central repository without having to redeploy entire
Axis2 web application?

What specific advantages I may derive by using a central remote repository (over deploying
or redeploying the entire Axis2 Web Application in application container (OC4J in our instance)?

Thank You Again


Shailesh




________________________________
From: AfkhamAzeez <afkham@gmail.com>
To: axis-user@ws.apache.org
Sent: Wed, January 13, 2010 11:56:04 PM
Subject: Re: Axis Clustering in OC4J Cluster

If you are deploying totally stateless Axis2 Web services, meaning,
you do not rely on stuff that you store in the Axis2 context
hierarchy, and you do not require Axis2 cluster management, then you
do not have to enable Axis2 clustering.

When nodes go down, if you require the requests to be redirected to
other nodes, you must front your cluster with an appropriately
configured load balancer which supports failover. Simply deploying
Axis2 in a cluster does not mean this will happen.

Axis2 supports URL repositories. Hence all your nodes in the cluster
can point to that URL repository. Again, this does not require you to
enable Axis2 clustering.

State replication is one part of clustering. What we mean by 'state'
is stuff saved in the Axis2 COnfigurationCOntext, ServiceGroupContext
& ServiceContext. This can be useful for stateful Web services and
even other Axis2 configuration items such as modules, deployers and so
on. For example, the WSO2 Caching module supports caching of requests
to improve performance. It maintains the cache as a map in the
ConfigContext. As you can see, this map has to be replicated across
all Axis2 nodes in the cluster. In such a scenario, clustering state
replication comes in handy.

HTH
Azeez

On Fri, Jan 8, 2010 at 10:53 PM, Shailesh Potnis <potnis2000@yahoo.com> wrote:
> Hi Azeez:
>
> Thank you for valuable input and links.  I think I went through the first
> link during my research and the axis2.xml clustering guide includes info
> from the second link.  I am still not clear about the end user use cases for
> stateless services.
>
> What I am trying to determine is:  Under what specific scenarios Axis2
> cluster deployed within OC4J cluster would provide additional value,  In
> other words what would be use cases for using Axis2 cluster within OC4J
> cluster that is fronted by OHS (Apache Web server) and a hardware load
> balancer?  I am trying to find this only for stateless services.
>
> During my discussion with some of my coworkers some possible use cases were
> discussed though I do not know if they would be provided by Axis2 Cluster.
> I would like to list them below:
>
> 1) In case a service is down in one Axis2 container, would Axis2 container
> redirect the request to another container -- I think the you provided
> (clustering at the servlet container level (HTTP session & request
> replication) is out of the scope of Axis2) indicates that this is not
> possible or out of scope. Correct me if this assumption is incorrect.
> 2) The second scenario is to be able to redeploy a single service (deployed
> with other services in a single J2EE war) using a central remote  repository
> -- this may not be related to cluster itself but would Axis clustering
> assist accomplishing this when OC4J standard deployment requires entire
> Axis2 war (potentially containing multiple services) to be redeployed.
> Would like to know whether this can be done using a central repository and
> Axis2 Admin console (with or without Axis2 cluster).
> 3) What are specific advantages of replicating ConfigurationContext,
> ServiceGroupContext & ServiceContext (For someone who has limited
> understanding of those objects) in Axis2 cluster for stateless services?
>
> Thank You and Best Regards
>
> Sincerely
>
> Shailesh
>
> ________________________________
> From: AfkhamAzeez <afkham@gmail.com>
> To: axis-user@ws.apache.org
> Sent: Fri, January 8, 2010 12:30:00 AM
> Subject: Re: Axis Clustering in OC4J Cluster
>
> We have not tested Axis2 clustering on OC4J AFAIK.
> With respect to state replication, at the Axis2 level, we are only
> concerned about replicating the values stored in the Axis2
> ConfigurationContext, ServiceGroupContext & ServiceContext. We use
> default Java serialization, hence the entire object tree should be
> serializable for the replication to be successful. Please note that
> clustering at the servlet container level (HTTP session & request
> replication) is out of the scope of Axis2 and has to be handled by the
> respective servlet containers.
>
> For more details; refer to my articles;
> 1. Introduction to WSO2 Carbon Clustering
> http://wso2.org/library/articles/introduction-wso2-carbon-clustering
> 2. WSO2 Carbon Cluster Configuration Language
> http://wso2.org/library/articles/wso2-carbon-cluster-configuration-language
>
>
> Azeez
>
> On Fri, Jan 8, 2010 at 1:29 AM, Shailesh Potnis <potnis2000@yahoo.com>
> wrote:
>>
>> Hi:
>>
>> I am going through a good deal of Axis2 documents and links.  I am trying
>> to determine if anyone has deployed Axis2 Cluster within OC4J cluster and
>> what is the experience.  I am planning to use it exclusively for stateless
>> web services.  Here are some specific questions:
>>
>> 1) What would be specific benefits of deploying the stateless web services
>> in Axis2 cluster when scalability would be provided by OC4J cluster?
>> 2) Are the Axis2 clustering benefits limited to deploying in Tomcat or are
>> useful in other app servers?
>> 3) In case a service is hung due to application or infrastructure issues,
>> would Axis2 cluster direct a request to another Axis2 instance in a cluster?
>>
>> I posted the above some time ago in the Axis2 developers group and I think
>> that this group may be a more appropriate group for this.
>>
>> Also when I deployed a stateless service (with a single stateless
>> operation: version), I get the following error:
>>
>> Could not send command message ContextClusteringCommandCollection to group
>> since it is not serializable
>>
>> I will be glad to send complete stack trace if necessary.
>>
>> All helpful suggestions are highly appreciated..
>>
>> Thank You and Best Regards
>>
>>
>> Sincerely
>>
>>
>> Shailesh
>>
>>
>
>
>
> --
> Thanks
> AfkhamAzeez
>
> Blog: http://afkham.org
> Developer Portal: http://www.wso2.org
> WSASBlog: http://wso2wsas.blogspot.com
> Company: http://wso2.com
> GPG Fingerprint: 643F C2AF EB78 F886 40C9  B2A2 4AE2 C887 665E 0760
>
>



-- 
Thanks
AfkhamAzeez

Blog: http://afkham.org
Developer Portal: http://www.wso2.org
WSAS Blog: http://wso2wsas.blogspot.com
Company: http://wso2.com
GPG Fingerprint: 643F C2AF EB78 F886 40C9  B2A2 4AE2 C887 665E 0760



      
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