seaside-dev February 2012

seaside-dev@lists.squeakfoundation.org

3 participants
4 discussions

cookie based sessions, RESTful urls no _k
by Nick Ager 22 Nov '12

22 Nov '12

Hi, In RESTful applications which also generate continuation key (_k) links a problem can arise if you open multiple tabs all sharing the same session. To illustrate: 1) Enable cookies for http://localhost:8080/examples/counter. 2) Open the counter and increment the value. 3) Open http://localhost:8080/examples/counter in a new tab and decrement the counter. 4) Return to the first counter and increment the value - you will see "-1" rather then "2" ! What I think is happening: If Seaside finds a session but there is no continuation key (_k) then WASession>>#handleFiltered: calls WARenderLoopMain>>#start which in turn creates a new root presenter and calls #initialRequest on the presenter. When the second tab is opened a new WACounter is created and stored in the session's #presenter property. When you return to the first tab, the callback is executed on the first counter, but the second counter is rendered. Ideas for possible fixes: * I thought that #presenter was backtracked so don't understand why the original counter #presenter isn't restored for the callback. If the presenter was backtracked correctly then the counter example should work as anticipated.... however: * in Pier (and potentially other RESTful apps) you don't want to create a new presenter for every RESTful call within an active session. If you don't create a new presenter then #initialRequest currently won't be called, which then won't allow your RESTful app to derive state from the url. If Seaside is modified to call #initialRequest do you need to differentiate between a call on a newly created session and one on an existing session? You could differentiate with a call to a new method on WAPresenter, pass in a flag to #initialRequest, or set a WARequestContext property to indicate a new session had been created. What to do with backtracked state. Do you nil all state before handling the request, restore state from a stored "initial value" snapshot or just use the state of the components from their last handled state? I bought this issue up before [1], but didn't pursue it as I was struggling to understand the issues and ran out of time. Julian responded to my previous email when I was proposing a problematic fix with: I'm not sure it's a good fix in the general case. If you don't have a > continuation key, you shouldn't (by definition) have any existing > (backtracked) state. Relying on the root presenter currently in the > Session is problematic since that value is backtracked for each > request; you'll simply get whichever root happened to be used by > whatever request was last handled by that session. If you don't happen > to be ever changing the root, then it may well be what you want, but > it's not right in the general case. > Incidentally, this also touches on the flaw I was discussing the other > week with our snapshots: because we have no continuation key, we > really ought to nil out any backtracked data before processing the > request (at least that way we have a consistent state while handling > the request). We don't run into the problem with the root presenter > because #start reinitializes it, but for other backtracked state, > you'd just get random stuff in there based on the last-handled > request. > A more appropriate general fix (at least in this case) could be to > take the last-used continuation and apply its state before handling a > request with no _k. However, we don't always know the last-used > (depending on the caching mechanism in place) and I'm not convinced > that is actually always what people want. I still feel pretty > confident that the "right" semantics of an Application/Session request > with no _k is to start a new main/render-loop. Certainly for Pier as it is currently designed I don't think that creating a new render-loop for session requests with the _k is the right thing to do, as it created a new root #presenter. I think ideally Seaside would for existing session with no _k 1) Keep the existing #presenter 2) call #initialRequest with a flag to indicate that a new session hadn't been created. 3) restore the state to an "initial render state" which is snapshotted (?) when the initial render occurs on a new session. Thoughts Nick [1] http://forum.world.st/sessions-continuation-keys-restful-urls-and-component… If each tabs starts with a RESTful url then a new presenter will be created.

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Relationship between Javascript-Core?
by Philippe Marschall 21 Feb '12

21 Feb '12

Hi We moved #jsonOn: from Javascript-Core to Seaside-JSON-Core. This makes implementing #jsonOn: much nicer because you can now use a canvas api. Instead of using JSStream#encodeDictionary:on: and #encodeCollection:on: and first having to convert them to dictionaries or collections you can "render" them similarly to components. However the dependencies between the JSON and Javascript packages are not yet clearly defined. Right now the dependencies are: - Seaside-JSON-Core depends on JSStream for encodeString:on: - Javascript-Core-JSON contains a JSON parser, right now this is only used by JQuery This opens the following questions: - What should the dependencies be? Should Javascript depend on JSON? Or vice versa? Or should they be independent? - Should we move JSJsonParser to Seaside-JSON-Core? - Should we rename Seaside-JSON-Core to JSON-Core? Cheers Philippe

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Re: Json, javascript-core and magritte json
by Philippe Marschall 18 Feb '12

18 Feb '12

2012/2/3 Norbert Hartl <norbert(a)hartl.name>: > Hi phillippe, > > I was talking to Nick about Magritte-Json and we discovered that there is a glitch in using seaside with javascript and magritte-json in paralllel. Magritte-Json implements GRObject>>#jsonOn: which (from a magritte-json point of view) should be implemented in Object. In Object and descendants javascript-core implements jsonOn: So after loading both the situation is that Object has a jsonOn: method from javascript-core, GRObject has one from Magritte-Json and GRSmallDictionary has again one from Javascript-core. Ah, cr... > What would be your idea how to solve this conflict? Thinking about it I don't find a solution to integrate both. I think at least one needs to step aside using method name prefix or the like. But maybe you have a _good_ idea how to solve it. They should obviously not conflict. First I though one should be renamed. However on second on thought wouldn't it be better to define Magritte-Json in terms of Seaside-Json? In addition: - Move #jsonOn: from Seaside-Javascript to Seaside-Json - make the argument of #jsonOn: a canvas like #renderOn: instead of a stream (this removes the need for JSJsonStream) - If we do all of this then we probably should move Seaside-Json from addon to core - While we're at it also move Seaside-REST to from addon to core All of these things would apply to 3.1 only. Cheers Philippe

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chrome prefetching URLs
by Philippe Marschall 12 Feb '12

12 Feb '12

Hi Didn't we once have an issue where a browser prefetched some links? Chrome seems to have a new feature "Chrome Instant" [1] that seems to do something similar. [1] http://www.google.com/chrome/intl/en-GB/webmasters-faq.html#instant Cheers Philippe

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seaside-dev February 2012