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Subject: [wsia] The search for per-entity-per-user Consumer state
- From: Gil Tayar <Gil.Tayar@webcollage.com>
- To: wsia@lists.oasis-open.org, wsrp@lists.oasis-open.org
- Date: Wed, 12 Jun 2002 13:16:12 +0300
Michael,
Your inclination
towards the "web approach" is largely based on scalability reasons - i.e. try to
reduce the amount of information the Consumer has to store per all entities per
all users. To that effect, let me try and continue to search for reasons why a
Consumer will _have_ to have information per-entity-per-user.
In the
discussion in the joint interfaces meeting yesterday, I suggested that the
Consumer would have to store (per-entity-per-user) whether to call performAction
or getFragment. You, rightly so, told me that you never liked the distinction so
that this is (not yet) a valid argument.
To tell
you the truth, I'm not sure *I* like the distinction between performAction and
getFragment. It may be that we will have *only* performAction, where the action
should be _exactly_ the "URL state" you mentioned in your point (a)
below.
Well, in this case, if the consumer has multiple portlets on the
page, it _must_ store the "last" action of all of them, and this _must_ be
per-user. To contrast with the web approach, in the simple Web application, the
browser stores the application's state in the address bar per-user. In the
WSRP/WSIA scenario, the Consumer must also store that information, per-portlet!
This is the only way to allow stateless portlets.
Am I missing
something?
Gil
-----Original Message-----
From: Michael
Freedman [mailto:Michael.Freedman@oracle.com]
Sent: Wednesday, June 12, 2002 00:19
To:
wsia@lists.oasis-open.org; wsrp@lists.oasis-open.org
Subject: Re: [wsia]
Follow-on Example
Eilon,
Oracle's approach/point of
view (on the web approach) is as follows:
a) we strongly
discourage portlets from maintaining any kind of
transient state. We
have found that even with moderate sized user
communities, stateless portlets
lead to significantly improved portal
response times. So our preferred
solution for your reservation scenario is
(0): there is neither a
session nor a transient entity. The reservation
state is maintained by
encoding the information in URLs inserted into the
generate response
content. I.e. only use sessions when state must be shared
between
entities.
b) recognizing that sessions will be used
however, the base scenario
should be one in which the two reservation
portlets cooperatively run in the
same session. In this scenario the
two portlets would be responsible for
namespacing encoding their session data
to avoid collisions. This is
analogous to the (servlet) web model
though obviously a more insidious
situation as servlets often (safely) assume
only one "instance" runs in a
session. All we would need to do to
support this would be ensure that a
portlet is able to determine and use a
"key" that distinguishes one use (on
a page) from another. If this
key/id were generated by the consumer, the
consumer could easily choose an
algorithm for generating such an id that is
repeatable without maintaining
any dynamic (state) information. Hence the
ID would have little/no
cost.
For us/me the above completely covers Approach 1: the
web approach. It
allows multiple entities of the same type to run in a
session with entity
private session data while still allowing these same
entities to share
session data between themselves of entities of other
types.
The outstanding question is whether we consider the situation
where a
portlet only has entity private data so common that we should allow
for them
to be so declared and mandate the consumer honor such a
declaration?
Personally, I think this is reasonable. Not having to
partition (namespace)
the session would be useful to such developers.
And I think this occurs
commonly enough for us to represent
formally.
Another scenario to consider is one where a set of entities
want to share a
session distinguished from another set running in the same
consumer. This
is a situation where a service provides 2 portlets
designed to work
together. For example a news feed display portlet and
a topic portlet. If
2 sets of these run is the same page how is one
set's session data isolated
from the other? My answer is that the
consumer merely chooses to establish
2 sessions (vs. one) and passes the
correct session ID to each set. I
further believe we shouldn't define
how a consumer chooses/learns to do
this. I.e. I don't think we should
define producer meta data that describes
potential groupings for its
sessions. Rather, portlets must expect that the
consumer will
potentially run all of these entities in the same session and
behave
accordingly. In many circumstances this may mean that the sets
trounce
each others shared data. However, well coded portlets could choose
to
represent this demarcation in its own settable configuration data for
the
portlets. I.e. the config screen could have a setting for group id
allowing
the page developer to set a common group id for the 2 portlets in
each set.
-Mike-
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