Re: More on FOM
On 30.Jun.2003 -- 10:29 PM, Sylvain Wallez wrote: Ricardo Rocha wrote: Sylvain Wallez wrote: Ricardo Rocha wrote: Imo, the flow renders actions (and modules outside the sitemap) unnecessary, so we shouldn't encourage their continued use by providing FOM-level support for them. The idea, in the long term, is to stop using actions (and xsp's, for that matter) in favor of the flow. That said, *indirect* access to modules and actions would satisfy short-term, transitional requests to allow reuse of such legacy components from the flow (if only by popular demand :-)). Ok. So we allow some abuse to satify transition of legacy applications or code. I'm happy with the suggested legacy.js in conjunction with the changes needed with regard to the object model. Nag : I still believe that creating a new, cut-down request, session, properties, cookie object for flow is unwise and we'd be better off ripping them out and go through modules instead. That would simplify the FOM a lot and yet would be more powerful. Chris. -- C h r i s t i a n H a u l [EMAIL PROTECTED] fingerprint: 99B0 1D9D 7919 644A 4837 7D73 FEF9 6856 335A 9E08
Re: More on FOM
Upayavira wrote: On 30 Jun 2003 at 22:29, Sylvain Wallez wrote: ... I suggested that components being heavyweight resource, allowing them to cross continuation boundaries should be prohibited. Automatic release doesn't seem a good solution to me, as it would mean that script variables would hold released components, thus leading to unpredictable behaviour (think about stateful pooled components). So my opinion is to raise an error if there are some unreleased components when a continuation is created. This will allow users to quickly learn the safe practices related to component management in flow scripts. I tend to agree. ... Once again, I agree that explicit release is very unnatural. But automagic release is good only if we can have some automagic restore. For this we can have getComponent() actually return a proxy to the real component, and have the proxy do a release/lookup when a continuation is suspended/reactivated. But as elegant this may seem, this won't work : stateful components have... a state, and a release/lookup cycle destroys this state. So I don't see any other solution... How about defining a FlowSafe interface (contains no state and can be released/looked up transparently), and maybe a FlowSerializable interface (has a way that the state can be stored into the continuation and then restored, all transparently? Continuations do not serialize state. Continuations restore the program counter and cause you to retain references to function invocations and local variables, however they do not roll back the values of those variables.
RE: More on FOM
Hi Ricardo, From: Ricardo Rocha [mailto:[EMAIL PROTECTED] Hi friends, The following items reflect the discussions Stefano and I have had around the FOM: - The load(uri) global function should be supported. This is clearly needed for nested source file inclusion (which map:script does not support). +1 - The cocoon.releaseComponent(component) method should be supported in conjunction with cocoon.getComponent(id). Further discussion is needed about whether the FOM implementation should automatically take care of releasing components. I'm with you that this part will need more investigation and use cases. But for now I'm fine without some automatism. So +1 too. - There should be unrestricted access to all components via cocoon.getComponent(id). I'll implement getComponent( id ) and releaseComponent( component) ASAP because the current flow implementation exposes the component manager and this leads to a serious bug! If you have more than one user the component manager can become null. This can be very annoying if you want to train some people ... Among other goodies, this will give indirect access to Actions and Modules without providing explicit FOM support for them. Access to request input modules, in particular, should account for request.getURI(). AFAIK many of them need the object model and this is not provided by the flow so I think you have no chance to use the actions and input modules which need objects of the object model. Am I right here? - Access to continuation objects should be provided. var kont = sendPageAndWait(uri, data) This is deemed necessary as certain continuation usage patterns may call for explicit, programmatic invalidation of continuations. - Properties - id - Methods - getParent() - getChildren() - invalidate() - Events - onExpiration() What do you guys think? sounds good. It should also be possible to create your own continuations objects without sending a page. See the JXForms implementation which needs this to provide previous/next-navigation. I'll add all those things to the proposal ASAP. Reinhard
Re: More on FOM
Ricardo Rocha wrote:
Hi friends,
The following items reflect the discussions Stefano and I have had
around the FOM:
- The load(uri) global function should be supported. This is clearly
needed for nested source file inclusion (which map:script does not
support).
- The cocoon.releaseComponent(component) method should be supported in
conjunction with cocoon.getComponent(id). Further discussion is needed
about whether the FOM implementation should automatically take care of
releasing components.
Hehe, I should go to Ecuador, as I advocated both ;-)
I suggested that components being heavyweight resource, allowing them to
cross continuation boundaries should be prohibited. Automatic release
doesn't seem a good solution to me, as it would mean that script
variables would hold released components, thus leading to unpredictable
behaviour (think about stateful pooled components). So my opinion is to
raise an error if there are some unreleased components when a
continuation is created. This will allow users to quickly learn the safe
practices related to component management in flow scripts.
- There should be unrestricted access to all components via
cocoon.getComponent(id).
Hehe again ;-)
Among other goodies, this will give indirect access to Actions and
Modules without providing explicit FOM support for them. Access to
request input modules, in particular, should account for
request.getURI().
Two remarks here :
- if we give access to request.getURI through an input module, then why
removing it from the request object ??
- modules need the object model and actions need it also, along with a
(Cocoon) resolver and a redirector. How will the flow be able to access
these objects to pass them to the components ?
IMO, the second point calls for some refactored interfaces since the
(Excalibur) resolver is now a regular component and we decided some time
ago to make the object model accessible through the Avalon context
(don't know if it has been implemented, though).
- Access to continuation objects should be provided.
var kont = sendPageAndWait(uri, data)
This is deemed necessary as certain continuation usage patterns may
call for explicit, programmatic invalidation of continuations.
- Properties
- id
- Methods
- getParent()
- getChildren()
- invalidate()
- Events
- onExpiration()
Sounds good.
What do you guys think?
Read inline !
Sylvain
--
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Re: More on FOM
Reinhard Pötz wrote: - There should be unrestricted access to all components via cocoon.getComponent(id). I'll implement getComponent( id ) and releaseComponent( component) ASAP because the current flow implementation exposes the component manager and this leads to a serious bug! If you have more than one user the component manager can become null. This can be very annoying if you want to train some people ... Cool :-) Among other goodies, this will give indirect access to Actions and Modules without providing explicit FOM support for them. Access to request input modules, in particular, should account for request.getURI(). AFAIK many of them need the object model and this is not provided by the flow so I think you have no chance to use the actions and input modules which need objects of the object model. Am I right here? Yes, you are... :-( - Access to continuation objects should be provided. var kont = sendPageAndWait(uri, data) This is deemed necessary as certain continuation usage patterns may call for explicit, programmatic invalidation of continuations. - Properties - id - Methods - getParent() - getChildren() - invalidate() - Events - onExpiration() sounds good. It should also be possible to create your own continuations objects without sending a page. See the JXForms implementation which needs this to provide previous/next-navigation. Yes, creating continuations without sending pages is all-important. I'll add all those things to the proposal ASAP. Hey Reinhard, you're a committed committer, cool! Regards, Ricardo
Re: More on FOM
Sylvain Wallez wrote: Ricardo Rocha wrote: The following items reflect the discussions Stefano and I have had around the FOM: - The load(uri) global function should be supported. This is clearly needed for nested source file inclusion (which map:script does not support). - The cocoon.releaseComponent(component) method should be supported in conjunction with cocoon.getComponent(id). Further discussion is needed about whether the FOM implementation should automatically take care of releasing components. Hehe, I should go to Ecuador, as I advocated both ;-) You're welcome anytime my friend! :-) I suggested that components being heavyweight resource, allowing them to cross continuation boundaries should be prohibited. Automatic release doesn't seem a good solution to me, as it would mean that script variables would hold released components, thus leading to unpredictable behaviour (think about stateful pooled components). So my opinion is to raise an error if there are some unreleased components when a continuation is created. This will allow users to quickly learn the safe practices related to component management in flow scripts. I see your point Sylvain. Your solution sounds somewhat draconian but it's probably the only safe bet... The question then becomes: does anyone envision real-world scenarios in which stateful components *are* needed across continuation boundaries? (if so, imo, it might imply curent Avalon component management isn't safe for continuations) Or can we *always* formulate our flow so that we don't need to keep component state across continuations? (for example, database connections can be acquired/released as needed precisely because they're pooled). On a separate thread, if *all* acquired components *must* be released prior to creating a continuation... wouldn't it make sense for the FOM implementation to automagically release them?? I know it may sound dangerous at first, but then again it would relieve developers from that tedious, anti-scripting release idiom... - There should be unrestricted access to all components via cocoon.getComponent(id). Hehe again ;-) Hahaha! There's nothing quite like the flavor of victory, is there? ;-) Among other goodies, this will give indirect access to Actions and Modules without providing explicit FOM support for them. Access to request input modules, in particular, should account for request.getURI(). Two remarks here : - if we give access to request.getURI through an input module, then why removing it from the request object ?? Until proven otherwise, I don't think getURI() is _needed_ by the flow, so the request object shouldn't expose it. Imo, the flow renders actions (and modules outside the sitemap) unnecessary, so we shouldn't encourage their continued use by providing FOM-level support for them. The idea, in the long term, is to stop using actions (and xsp's, for that matter) in favor of the flow. That said, *indirect* access to modules and actions would satisfy short-term, transitional requests to allow reuse of such legacy components from the flow (if only by popular demand :-)). - modules need the object model and actions need it also, along with a (Cocoon) resolver and a redirector. How will the flow be able to access these objects to pass them to the components ? Yes, you're right. Reinhard also pointed this out. IMO, the second point calls for some refactored interfaces since the (Excalibur) resolver is now a regular component and we decided some time ago to make the object model accessible through the Avalon context (don't know if it has been implemented, though). Yes, this solution is clean. If the object model is available legacy actions would be accessible. What I'd oppose -in any case- is giving actions/modules first-class status in the FOM... Ricardo
Re: More on FOM
Ricardo Rocha wrote: Sylvain Wallez wrote: Ricardo Rocha wrote: The following items reflect the discussions Stefano and I have had around the FOM: - The load(uri) global function should be supported. This is clearly needed for nested source file inclusion (which map:script does not support). - The cocoon.releaseComponent(component) method should be supported in conjunction with cocoon.getComponent(id). Further discussion is needed about whether the FOM implementation should automatically take care of releasing components. Hehe, I should go to Ecuador, as I advocated both ;-) You're welcome anytime my friend! :-) Cool ! This is one of the good things of Apache : world-wide friends, ready to welcome you for good time and geek talks :-) I suggested that components being heavyweight resource, allowing them to cross continuation boundaries should be prohibited. Automatic release doesn't seem a good solution to me, as it would mean that script variables would hold released components, thus leading to unpredictable behaviour (think about stateful pooled components). So my opinion is to raise an error if there are some unreleased components when a continuation is created. This will allow users to quickly learn the safe practices related to component management in flow scripts. I see your point Sylvain. Your solution sounds somewhat draconian but it's probably the only safe bet... The question then becomes: does anyone envision real-world scenarios in which stateful components *are* needed across continuation boundaries? (if so, imo, it might imply curent Avalon component management isn't safe for continuations) Or can we *always* formulate our flow so that we don't need to keep component state across continuations? (for example, database connections can be acquired/released as needed precisely because they're pooled). Databases connections are a good use case. IMO, the sequential nature of a flow script will make people want to keep stateful components as the do in standard code, as it is somewhat unnatural to release a connection just before a sendPageAndWait() and then look it up just after. The modified Rhino intepreter has some extensions to exception management to allow clearing and restoring variables when a continuation is suspended/reactivated. This will be very useful in large scripts when a continuation is suspended several function call deeper than the location where the component is used. On a separate thread, if *all* acquired components *must* be released prior to creating a continuation... wouldn't it make sense for the FOM implementation to automagically release them?? I know it may sound dangerous at first, but then again it would relieve developers from that tedious, anti-scripting release idiom... Once again, I agree that explicit release is very unnatural. But automagic release is good only if we can have some automagic restore. For this we can have getComponent() actually return a proxy to the real component, and have the proxy do a release/lookup when a continuation is suspended/reactivated. But as elegant this may seem, this won't work : stateful components have... a state, and a release/lookup cycle destroys this state. So I don't see any other solution... - There should be unrestricted access to all components via cocoon.getComponent(id). Hehe again ;-) Hahaha! There's nothing quite like the flavor of victory, is there? ;-) Mmmh... it's not about victory in the fight meaning, where there's a winner and a looser. We all win in discussing our thoughts and taking good ideas where they come. This time these are mine and, well, this feels good ;-) Among other goodies, this will give indirect access to Actions and Modules without providing explicit FOM support for them. Access to request input modules, in particular, should account for request.getURI(). Two remarks here : - if we give access to request.getURI through an input module, then why removing it from the request object ?? Until proven otherwise, I don't think getURI() is _needed_ by the flow, so the request object shouldn't expose it. Actually, I think that if the flow needs something from the URI, this information should be passed by the sitemap through map:parameters in the map:call. The sitemap is responsible for handling the URI space, including extracting information from it for other components. Imo, the flow renders actions (and modules outside the sitemap) unnecessary, so we shouldn't encourage their continued use by providing FOM-level support for them. The idea, in the long term, is to stop using actions (and xsp's, for that matter) in favor of the flow. That said, *indirect* access to modules and actions would satisfy short-term, transitional requests to allow reuse of such legacy components from the flow (if only by popular demand :-)). Ok. So we allow some abuse to satify transition of legacy applications or code. -
Re: More on FOM
On 30 Jun 2003 at 22:29, Sylvain Wallez wrote: ... I suggested that components being heavyweight resource, allowing them to cross continuation boundaries should be prohibited. Automatic release doesn't seem a good solution to me, as it would mean that script variables would hold released components, thus leading to unpredictable behaviour (think about stateful pooled components). So my opinion is to raise an error if there are some unreleased components when a continuation is created. This will allow users to quickly learn the safe practices related to component management in flow scripts. I tend to agree. ... Once again, I agree that explicit release is very unnatural. But automagic release is good only if we can have some automagic restore. For this we can have getComponent() actually return a proxy to the real component, and have the proxy do a release/lookup when a continuation is suspended/reactivated. But as elegant this may seem, this won't work : stateful components have... a state, and a release/lookup cycle destroys this state. So I don't see any other solution... How about defining a FlowSafe interface (contains no state and can be released/looked up transparently), and maybe a FlowSerializable interface (has a way that the state can be stored into the continuation and then restored, all transparently? So you would have to consciously code your components to use either of these interfaces, otherwise you'll have to manually release them before creating a continuation. Upayavira
