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From Paul Fremantle <pzf...@gmail.com>
Subject Re: [Axis2] Thoughts on making Session Model independent of the InformationModel [Ctx Heirachy]
Date Tue, 07 Feb 2006 08:10:10 GMT
Rajith

I agree about the info model. You give every instance an identical config by
some file or URL distribution, and then distribute sessions. +1

Paul

On 2/2/06, Rajith Attapattu <rajith77@gmail.com> wrote:
>
> Hi Srinath,
>
> Sorry for the late reply.
>
> Well it really wouldn't be a distributable information model. I think it
> would be correct to say that we will have identical static configuration
> across all nodes.
>
> I don't think we should distribute during runtime any information within
> the information model to any node. As Paul mentioned "The standard context
> is the same on each machine, because the configuration, etc should be the
> same" , so we are talking about making identical standard contexts across
> nodes through deploy time confirguration.
>
> Did I answer your question properly?
>
> Btw, can u give me a use case where u would need to change (hence
> distribute across) the normaly static info, within the information model
> during runtime ?
> This would help me to understand your question more.
>
> Also even if there is a case like that then it's far more easy to do that
> config change manualy on every node than building infrastructure to cater to
> an exception.
>
> Clustering is a huge overhead and only the bare minimum should
> be clustered around so to avoid the performance and other problems it poses.
>
> Regards,,
>
> Rajith
>
> On 1/31/06, Srinath Perera <hemapani@gmail.com> wrote:
> >
> > Thanks Paul, Rajith .. got the point.
> >
> > One more Q? when we cluster Axis2, should be distribute (at least
> > somepart of)  information model.  Distributed deployment means more or
> > less distributed information Model IMHO
> >
> > Thanks
> > Srinath
> >
> > On 1/31/06, Paul Fremantle <pzfreo@gmail.com > wrote:
> > > Rajith
> > >
> > > +1
> > >
> > > I think the main aspect is simply this:
> > >
> > > If we have a cluster of Axis2, I can get my request directed to any
> > server
> > > in the cluster. The standard context is the same on each machine,
> > because
> > > the configuration, etc should be the same. But the session data is
> > specific
> > > to my interaction, and must be moved from machine to machine. Without
> > making
> > > this simple, standalone and lightweight we cannot cluster a session
> > based
> > > interaction.
> > >
> > > Paul
> > >
> > >
> > > On 1/30/06, Rajith Attapattu <rajith77@gmail.com> wrote:
> > > >
> > > > Srinath,
> > > >
> > > > Let me explain a bit more behind my thinking.
> > > >
> > > > When you look at clustering sessions we need to have a clear
> > abstraction
> > > of a session and session manager and it has to be light weight.
> > > >
> > > > This gives you the following flexibility.
> > > >
> > > > a) if it's not deployed in clustered mode then you run install a
> > > LocalSessionManager (could be the default)
> > > >
> > > > b) if it's deployed in clustered mode then you install a
> > > RemoteSessionManager
> > > >
> > > > c) if u need to persist the session (for failover and recovery) then
> > u
> > > need to decorate a SessionManager with a PersistantSessionManager
> > > >
> > > > d) Your base remote session manager can be decorated to use JGroups
> > or
> > > WADI or ActiveCluster to use as the remoting platform
> > > >
> > > > e) You can decorate your base  PersistantSessionManager to be DB
> > backed or
> > > file backed..etc
> > > >
> > > > None of the above is possible with the Information model. It's very
> > rigid
> > > and definitely not light weight.
> > > > the information model is designed for a different purpose.
> > > >
> > > > Look at other projects (for ex Geronimo) they also have a light
> > weight
> > > session model thats independent of any other mechanism.
> > > >
> > > > Frankly I don't know how the clustering will work if it's tied to
> > the
> > > information model, besides it will complecated to wire in the
> > clustering
> > > code to the information model.
> > > >
> > > > Why not keep it simple, a handler can did in the sesion and inject
> > it to
> > > the message context.
> > > >
> > > > I agree that information model is to manage information (but I argue
> > that
> > > it should be limited to manage service specific information)
> > > >
> > > > Remember a session can be far beyond the scope of a single axis2
> > instance.
> > > A session can span across multiple nodes or even multiple clusters. A
> > > session can exist between an Axis2 instance and a .Net System or some
> > other
> > > SOAP stack. Look at the following use case
> > > >
> > > >
> > > > Client -------> (Accounting system [Runs on Axis2])  ------ (may
> > have to
> > > acess the payroll system) --------> (Payroll system [Runs on XFire] )
> > > >
> > > > (I know we don't support this now (maybe in the future with
> > WS-Context)
> > > !!! )
> > > >
> > > > Lets say the client requets to print Monthly account and it has to
> > get
> > > some information from the Payroll system
> > > > In such a situation we can't ask the client to reauthenticate with
> > the
> > > payroll system. As far as the client is concerned it's a single
> > session for
> > > him, doesn't care wether it spans several systems as long as it's
> > > transparent to the client.
> > > >
> > > > Regards,
> > > >
> > > > Rajith.
> > > >
> > > >
> > > >
> > > > On 1/30/06, Srinath Perera <hemapani@gmail.com > wrote:
> > > > > Hi Rajith;
> > > > >
> > > > > Information model is for manging the information .. (with there
> > > > > scopes). Session should be part information model.
> > > > >
> > > > > You need something with global scope to store the map that
> > cantains
> > > > > session, that should be part of information model
> > > > >
> > > > > Thanks
> > > > > Srinath
> > > > >
> > > > > On 1/27/06, Rajith Attapattu < rajith77@gmail.com> wrote:
> > > > > >
> > > > > >  Hi Guys,
> > > > > >
> > > > > >  What are your thoughts on making the Session Model independent
> > of the
> > > > > > Information Model or more specifically the Context Heirachy.
> > > > > >
> > > > > >  1. If we sperate the two areas then both models can evolve
> > > independently of
> > > > > > each other without limiting the growth of each other.
> > > > > >
> > > > > > 2. From a scalability point of view I don't think it's good
idea
> > to
> > > couple
> > > > > > the "session" with the context heirachy.
> > > > > >
> > > > > > 3. Currently there is no clearly boundries wrt to where the
> > scope
> > > begings or
> > > > > > ends with ServiceGroupContext and ServiceGroup. I got mixed
> > answers
> > > about
> > > > > > the usage and usefulness of these.
> > > > > >
> > > > > > Let me quote from one of email to the Session mgt proposal
> > thread.
> > > > > >
> > > > > >
> > > > > > a) The Session model should be lightweight and clearly defined
> > with
> > > proper
> > > > > > boundries.
> > > > > >
> > > > > > b) It should not be tied to any other model as it might be
> > > architecurally
> > > > > > unstable as there want be a clear demarcation point.
> > > > > >
> > > > > > c) when things start to move across the wire (Session
> > replication)
> > > having a
> > > > > > clean, well defined session model is very very important.
> > > > > >
> > > > > > Right now the most critical shortcomming of Axis2 as I
> > understand is
> > > that we
> > > > > > don't have a clear picture of what a session is wrt to the
> > current
> > > Axis2
> > > > > > architecture.
> > > > > > I gues Srinath mentioned that same thing to me.
> > > > > >
> > > > > > My suggestion is we should evolve the Session Model
> > independently of
> > > > > > anything else and inject it to the ServiceAuthor via the message
> > > context by
> > > > > > way of a handler.
> > > > > >
> > > > > > If we do that we want have any limitation or complications of
> > > associating it
> > > > > > with ServiceGroups or anything like that.
> > > > > >
> > > > > >
> > > > > > What do u guys think???
> > > > > >
> > > > > > Regards,
> > > > > >
> > > > > > Rajith.
> > > > >
> > > > >
> > > > > --
> > > > > ============================
> > > > > Srinath Perera:
> > > > >     http://www.cs.indiana.edu/~hperera/<http://www.cs.indiana.edu/%7Ehperera/>
> > > > >    http://www.bloglines.com/blog/hemapani
> > > > >
> > > >
> > > >
> > >
> > >
> > >
> > > --
> > > Paul Fremantle
> > > VP/Technology, WSO2 and OASIS WS-RX TC Co-chair
> > >
> > > http://bloglines.com/blog/paulfremantle
> > > paul@wso2.com
> > >
> > > "Oxygenating the Web Service Platform", www.wso2.com
> > >
> >
> >
> > --
> > ============================
> > Srinath Perera:
> >    http://www.cs.indiana.edu/~hperera/<http://www.cs.indiana.edu/%7Ehperera/>
> >   http://www.bloglines.com/blog/hemapani
> >
>
>


--
Paul Fremantle
VP/Technology, WSO2 and OASIS WS-RX TC Co-chair

http://bloglines.com/blog/paulfremantle
paul@wso2.com

"Oxygenating the Web Service Platform", www.wso2.com

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