Re: [wsrp] Scoping of Transient Properties - Mapping to JSR286

[Rich Thompson <richt2@us.ibm.com>]

We had talked about transient properties
changing into an interface style (like navParams) rather than the current
storage style. The problem one runs into is that not all Portlets are interacted
with in every user request lifecycle and so the Consumer would have to
implement a means of remembering to which Producer it already sent a particular
new value. Another option would be to move transientProperties into MarkupParams
such that they participate in any cache key. That would handle the case
of portlets being rendered on the current page, but would also decrease
the value of fragment caching (and miss use cases related to portlets not
on the current page).

I think these were the core reasons
that drove us toward making transient properties state oriented rather
than interface oriented. (btw: I noticed on my pass trying to reasonably
normalize navParams and transProps that the decision to change navParams
into an interface style wasn't well-reflected through cd01 ... I am making
those changes for wd15.) It seems to me that the potential reduction in
transmitted data isn't worth the added Consumer complexity. While I don't
think it would be horrible to require Producers to cache received transient
properties, I guess I'm not seeing a good value/cost trade-off driving
us in that direction.

Rich

Stefan Hepper <sthepper@hursley.ibm.com>

03/31/06 03:18 AM

To	OASIS WSRP TC <wsrp@lists.oasis-open.org>
cc
Subject	Re: [wsrp] Scoping of Transient Properties - Mapping to JSR286

But wouldn't it be more efficient in any case (independent
from the 
producer implementation) to define these properties as shared at 
producer level and only send the changes in each request instead of 
sending all properties that a portlet has described to in each request?

Or, as another alternative, can we modify the current spec so that the
consumer is allowed to only send changed values and the producer needs
to cache the values)?

Stefan

Rich Thompson wrote:
> 
> While I am sympathetic to the use case where several Portlets at a
> single Producer tend to use session properties to share state with
each 
> other and that this shared state could form a convenient means of
> indicating interesting transient properties, I think it is stretching
> too far to say such properties are shared across all Portlets hosted
by 
> that Producer. The stateful items that are being shared really are
> portlet-specific.
> 
> As to whether this causes a problem for a Producer who is mapping
these 
> into shared state and potentially receiving two inputs declaring the
> same value with a potential negative side effect of firing listeners
> multiple times for what is really a single state change, I would 
> encourage Producers with such an issue to look at their copy of the
> stateful item (i.e. keep a copy locally and manage the missing =>
null 
> semantics within the handler for transient properties) and do a value
> comparison before setting the value. This avoids the 'local' issue
> related to how the Producer is mapping transient properties without
> percolating that issue outside of the Producer.
> 
> BTW: I think you provide good reasons why JSR286 should choose to
map 
> transient properties to shared session attributes, I just don't see
why 
> that local architectural decision needs to impact the external WSRP
> protocol.
> 
> Rich
> 
> 
> *Subbu Allamaraju <subbu@bea.com>*
> 
> 03/30/06 12:58 PM
> 
>                  
> To
>                  OASIS
WSRP TC <wsrp@lists.oasis-open.org>
> cc
>                  
> Subject
>                  [wsrp]
Scoping of Transient Properties - Mapping to JSR286
> 
> 
>                  
> 
> 
> 
> 
> 
> Based on the discussions we had in the JSR286 EG, I was asked to raise
> this topic. Stefan - please step in if you find any items I missed.
Mike
> 
> The basic question is what is the natural scoping for specifying these
> properties - in the PortletDescription or the ServiceDescription?
> 
> Since most web development platforms provide some notion of sessions,
we
> (the EG) find it natural to manage session-scoped transient properties
> via a native session that is already available to web apps. For example,
>  in a J2EE web app, a session-scoped transient property can be
mapped
> to an attribute in the HttpSession (or the PortletSession). There
are
> two advantages to such a mapping:
> 
> - Portlet developers are used to using session attributes. To make
a
> change to an attribute shared across portlets, the developer/deployer
> could simply mark that a given session attribute should be made
> available to other portlets via a remote protocol such as WSRP.
> 
> - Secondly, this also allows legacy apps or apps built using other
web
> programming models to rely on session attributes transparently. Those
> apps don't have to use special new APIs to take advantage of transient
> properties.
> 
> However, such a mapping of session-scoped transient properties to
native
> session attributes on web containers would bring in one potential
problem.
> 
> In WSRP, session scoped transient properties are defined on each
> portlet, where as sessions are globally accessible to all components
in
> a web app. That is multiple portlets deployed on a given producer
can
> share the same session, and hence a portlet-level specification of
these
> properties does not make sense for web developers.
> 
> To take an example, portlets deployed on a producer may be interested
in
> sharing two session attributes TP1 and TP2 with other portlets deployed
> on other producers. Accordingly, the producer will expose TP1 and
TP2 as
> transient properties required for *each* portlet deployed on that
producer.
> 
> When a consumer has a value for one of these properties, it will then
> send the same property to each portlet on the producer. In most cases,
> this is duplication of traffic, and takes extra effort for both the
> consumer and producer. Producers running on J2EE web containers will
> also have to worry about session attribute listeners, clustering etc,
> since changes to attributes will typically involving invoking these
> listeners, and replicating the attribute to other nodes in a cluster.
> 
> (I'm speaking here from J2EE's point of view, and it would be
> interesting to see what is natural from .NET side. Mike - any comments?)
> 
> Given this, my question is whether specifying transient properties
makes
> sense at the portlet level? It seems more natural to specify these
in
> the ServiceDescription instead, and treat those like other data stored
> in the session (e.g. URL templates, or user profiles).
> 
> Regards,
> 
> Subbu
> 
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