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Subject: Re: [wsrp] Session scoped transient properties.
I agree with Subbu. Another thing we should keep in mind is what will happen when we support SOAP 1.2 which defines a HTTP binding and support for HTTP GET. Getting us too much into the direction that GR /GM are potentially state changing operations might get us into problems there. I'm not sure I get the argument about the bridges. I can see this for the producer side session, but as the transient properties are something new that currently does not exist in the web world I don't see why current bridges would rely on this. I can see the argument that transient properties are similar to producer side session state and thus we may want to have it consistent, but on the other side everyone agrees that it is a bad thing to change transient properties in GR/GM so why allow this and make the consumer more complex? Stefan Subbu Allamaraju wrote: > I agree with Rich's point on idempotency. From the web developer's point > of view, you are right that this requirement forces some constraints, > and developers may find this awkward when you try to explain why it is a > bad idea to change state during a getMarkup. But from the protocol's > point of view, if we relax the idempotency requirement, there will be > some negative consequences. There will be less guarantee for such > session scoped transient properties to work. Portlets may think that > they are able to make state changes, but those may remain local, or may > get lost on a subsequent call. There is another point we need to > consider. If we allow request scoped properties in future, it would be > hard to match it with getMarkup. > > Subbu > > Michael Freedman wrote: >> I agree completely. The issue comes down to whether our protocol >> enforces the convention or merely identifies it as best practice. If >> we allow the return of transientProperties I would expect us to >> provide clarifying terms that reference a best practice statement (or >> some such thing). As for the unexpected behavior: Noted that the >> problem is worse, but in many portlet environments changing session >> state can impact other portlets in that producer and hence portlet >> developers have to recognize/avoid getting themselves into a fix. >> Which brings us back to the question then of why should we allow this >> in the first place? I believe you answered that in your message when >> you described that in the existing web world containers pass this >> issue to component developers. The reality is these are some of the >> same component developers wanting to provide portlets. Many come from >> a perspective/expectation that they should be able to adapt their >> existing component code quickly and easily into the portlet >> environment (some in fact don't even know they are running as portlets >> as that adaption is done underneath them by the MVC system/bridge >> technology). Right now our design forces these vendors to rewrite >> their existing work which delays their migration. -Mike- >> >> Rich Thompson wrote: >>> >>> This likely revolves around how one views idempotency and the WSRP >>> protocol. >>> >>> It has been frequently argued that there is a straight-forward >>> mapping of the HTTP verbs to WSRP operations and, in particular, that >>> getMarkup and getResource are idempotent operations. Whether one >>> agrees with that assertion or not, there is the next level of issue >>> in that many sites relax idempotency to only include transactional >>> items and not 'trivial' things (such as hit counters) or the caching >>> of items in a user session. It is often these use cases that drive >>> container decisions to not enforce the idempotent requirements of >>> certain interactions, but rather to pass the issue on to component >>> developers. At this philosophical level, a key question is whether >>> adding the ability to return transientProperties with response to GM >>> and GR wouldn't be a declaration that these aren't really idempotent >>> interactions. (The "container" is allowing non-idempotent behavior >>> without knowledge as to whether it will be used in a "transaction" >>> manner ... and components can not determine this either.) >>> >>> On a practical level, it seems like adding this feature would cause >>> page refreshes to exhibit unexpected behavior. Consider when portlet >>> A generates its markup and then portlet B updates a transient >>> property both receive. A page refresh would cause a change in the >>> markup from portlet A which would likely be unexpected in many cases >>> and would definitely exhibit that the page wasn't conforming to >>> idempotent requirements. I'm not sure this is entirely a bad thing, >>> but it shouldn't be taken lightly either. >>> >>> Rich >>> >>> >>> *Michael Freedman <michael.freedman@oracle.com>* >>> >>> 03/21/06 04:28 PM >>> >>> >>> To >>> wsrp <wsrp@lists.oasis-open.org> >>> cc >>> >>> Subject >>> [wsrp] Session scoped transient properties. >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> Currently we don't allow getMarkup and getResource to return >>> transientPropertyUpdates; only performBlockingInteraction and >>> handleEvents can. Should we remove this restriction? >>> >>> Currently, we don't allow navigational state, mode, window state changes >>> from getMarkup/getResource because we can't ensure the consumer can >>> implement reasonable semantics. To a lesser extent we disallow this >>> because our model discourages state changes during render. However, >>> because we can't control internal producer session state this is a >>> convention not something that can be fully enforced. >>> >>> I believe setting transient session properties at GM/GR time can be >>> semantically defined -- its no different then doing such a thing locally >>> in a concurrent world. I.e. the consumer honors such sets immediately >>> [as with handleEvents]. So, though we would continue to want to >>> discourage transient property state changes should we prevent it merely >>> on the grounds that its not our preferred model? >>> >>> What we lose by having this restriction are degrees of freedom in how >>> environments built on top of wsrp that ease portlet development will >>> expose this concept. One reasonable model [that JSR 286 is currently >>> advocating] is to not distinguish within portlet code between transient >>> session properties and producer session properties. From a code >>> perspective there are just session properties. The code reads/writes >>> these values without explicit knowledge as to whether the value is >>> shared with the consumer. That detail is described in >>> configuration/metadata. The JSR 286 container is responsible for moving >>> the appropriate values to/from the session from/to the consumer. Like >>> wsrp, the jsr discourages session state changes during >>> render/getresource. Also like wsrp it doesn't prevent such changes. >>> With the current restriction the JSR is faced with either tightening its >>> requirements to throw an exception if any session writes are attempted, >>> allowing the local writes but throw an exception for those session >>> properties that are shared [transient], or merely updating the values >>> locally but not returning such state to the consumer [meaning these >>> updates will be lost on the next request as the transient properties are >>> pushed again with the old values]. All three of these are behaviors >>> will be foreign to java [web app] developers. >>> -Mike- >>> >>> >>> >>> --------------------------------------------------------------------- >>> To unsubscribe from this mail list, you must leave the OASIS TC that >>> generates this mail. You may a link to this group and all your TCs >>> in OASIS >>> at: >>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php >>> >>> >>> --------------------------------------------------------------------- >>> To unsubscribe from this mail list, you must leave the OASIS TC that >>> generates this mail. You may a link to this group and all your TCs in >>> OASIS at: >>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php > > > --------------------------------------------------------------------- > To unsubscribe from this mail list, you must leave the OASIS TC that > generates this mail. You may a link to this group and all your TCs in > OASIS > at: > https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php > >
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