RE: [Zope-dev] 'transparent' proxying to a method not in your nam espace?
Were you able to call a method within a namespace for which it did not actually exist in this case? If so, that's sort of what I am after, except instead of user directory service, I'm thinking more along the line of a method directory service for said lookups and method calling. More specifically, I got this _really_ crazy idea into my head... ever since Jim's OSCON Components BOF, my brain has been trying to wrap around high-level use-cases of how it could be useful. That got me thinking a lot about a folder that I have that is bloated with all sorts of stuff; thousands of objects (mostly content), with dozens in the main folder - including code, presentation, sql, and content objects all over the place, and no matter how well I try to organize them, it still seems really messy - but it wouldn't be in service-oriented world. My interest is motivated by some frustrations with Transparent Folders. What I'm actually thinking of, I guess, is a little bit more ambitious: a lightweight 'interim' component/services type of system with a method directory/catalog service; let me explain: I have a folder - let's call it 'Content' - and it doesn't have a method I need to do something, for example, like an automation task set up in a TTW python script. In my ideal vision here, the method can be stuffed off in a central 'Code' folder located somewhere else in the odb hierarchy; My 'Content' folder needs a method called 'purgeExpiredContent' as an automation task. 'purgeExpiredContent' exists in the 'Code' folder; 'Content' doesn't have anything called 'purgeExpiredContent' but 'Content' is not a normal folder - it is a SuperMagicalGeniusFolder(TM) (perhaps there is a better name); if the folder had a dialog with itself, this is the conversation it would have: .................... "Someone just asked me to run a method called purgeExpiredContent. Do I have a method called that in my namespace?" "No." "Ok, I need to find it elsewhere; before I look in the namespace stack using acquisition, I am going to look up in a directory service if the method exists elsewhere. Does the Method Directory Service indicate it knows where this method lives?" "I just queried it, and it does know where this method lives; the path:..." "Ok, I got that path... " "I found the method; I'm going to run it within my ('Content') namespace." "Ok, I'm done..." .................... In this case, the method 'purgeExpiredContent' is more of a service to the 'Content' folder. The 'Method Directory Service' was likely a ZCatalog-derived lookup 'service object' in the Zope root; it's query result contained the path needed for 'Content' to obtain and run the method from wherever it lived (in this case, a folder called 'Code' in the Zope root, but using a method directory service, it really could live anywhere). The 'Content' folder had the smarts to intelligently look in the 'method directory' for methods it didn't have before it traversed its acquisition parents looking for it. It should be said that this feature should be provided via acquisition to contained objects below this SuperMagicalGeniusFolder(TM) called 'Content' and would use the namespace of the object it is called upon. This would make partitioning code, content, and presentation a lot easier. A method directory service and a smart folder like that could even use (optionally, in a componentized universe) as a 'method directory service' query parameter the interface asserted by the object trying to get the method as a means to determine if an method actually can be obtained; the catalog would return no resulting method even if it existed, but didn't work with the correct interface... I know I should just be patient and wait for component architecture ('cause yes, I now really see a need for it), but this idea is just stuck in my head, and I can't get it out cause it seems so useful... and it seems to me that one could use a modified ZCatalog as a good directory service for method lookups. I guess the complicated question (for me, at least) is whether or not the process of acquisition could be interrupted and/or preempted for an alternate traversal means for obtaining methods either inside my Product code or in a hotfix product. The concept of method lookup doesn't seem daunting, but making it execute transparently does. I would hope something like this would be possible without modifications to the Zope core... Sean -----Original Message----- From: Dyon Balding [mailto:dyon.balding@monster.com] Sent: Wednesday, August 08, 2001 10:15 AM To: sean.upton@uniontrib.com Cc: zope-dev@zope.org Subject: Re: [Zope-dev] 'transparent' proxying to a method not in your namespace? Sean, I think I understand what you're trying to do; if so, I've done something similar. What I had was a list of staff members pulled from LDAP, and a folder containing objects representing some of those staff members (those who had customized their information). The URLs from the staff list page were all the same, ie blah/staff/name or similar. I then had a site access_rule that grabbed and rendered the customized object if it existed, or retrieved some generic information from LDAP and rendered it if it didn't. I think that's approximately what you're trying to do? If the above method sounds plausible I can give you a copy of my code if it's any help. -d On Wed, Aug 08, 2001 at 09:22:51AM -0700, sean.upton@uniontrib.com wrote:
Problem: I have a custom folder type, and I want to hijack unsuccessful method lookups in its namespace and have them transparently proxy to code in another folder...
I have a Python product class that uses Folder as it's base; it's cluttered with code objects, and I don't want to have to use Transparent Folders, which seem to break one thing or another. I'm also looking for (perhaps) something as an application-specific alternative/addition to acquisition as a namespace traversal mechanism.
I had this idea of storing my various methods in a 'ProjectCode' folder in the Zope root, and having my 'Folder' evaluate its own namespace looking for a method; if it doesn't exist, before the Zope looks in the acquisition parent(s), the 'Folder' looks in the namespace for the 'ProjectCode' (or some other folder name) folder in the root to find the method, and run it within the 'Folder' namespace.
I'm sort of ignorant as to where to start looking if I wanted to do this, but I'm willing to investigate and figure out how to code it if it's something that can be done within my product code or in a hotfix, and doesn't require a patch the size of Texas...
Thoughts?
Sean
========================= Sean Upton Senior Programmer/Analyst SignOnSanDiego.com The San Diego Union-Tribune 619.718.5241 sean.upton@uniontrib.com =========================
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-- | Dyon Balding . Software Engineer . HiringTools.Monster.com | dyon@hiringtools.com . +1 415 288 3375
sean.upton@uniontrib.com wrote:
[snip]
.................... "Someone just asked me to run a method called purgeExpiredContent. Do I have a method called that in my namespace?" "No." "Ok, I need to find it elsewhere; before I look in the namespace stack using acquisition, I am going to look up in a directory service if the method exists elsewhere. Does the Method Directory Service indicate it knows where this method lives?" "I just queried it, and it does know where this method lives; the path:..." "Ok, I got that path... " "I found the method; I'm going to run it within my ('Content') namespace." "Ok, I'm done..." ....................
So from what I read here, the namespace of this folder should be just after the namespace of the object, but before the general containment namespace stack, right?
In this case, the method 'purgeExpiredContent' is more of a service to the 'Content' folder. The 'Method Directory Service' was likely a ZCatalog-derived lookup 'service object' in the Zope root; it's query result contained the path needed for 'Content' to obtain and run the method from wherever it lived (in this case, a folder called 'Code' in the Zope root, but using a method directory service, it really could live anywhere). The 'Content' folder had the smarts to intelligently look in the 'method directory' for methods it didn't have before it traversed its acquisition parents looking for it.
I would think the way to handle this would be to push this 'method directory service' namespace into the namespace object multi-mapping right before the object was executed. I don't think this would require too much in the way of coding, and would still rely on the built-in acquisition framework. It would be like automatically wrapping a with statement around the call.
It should be said that this feature should be provided via acquisition to contained objects below this SuperMagicalGeniusFolder(TM) called 'Content' and would use the namespace of the object it is called upon.
This would make partitioning code, content, and presentation a lot easier. A method directory service and a smart folder like that could even use (optionally, in a componentized universe) as a 'method directory service' query parameter the interface asserted by the object trying to get the method as a means to determine if an method actually can be obtained; the catalog would return no resulting method even if it existed, but didn't work with the correct interface...
You could create a simple subclass of folder that registers itself into this "MDS" namespace when it is created. Then a hotfix could push in this namespace at the appropriate point in the object publication process.
I know I should just be patient and wait for component architecture ('cause yes, I now really see a need for it), but this idea is just stuck in my head, and I can't get it out cause it seems so useful... and it seems to me that one could use a modified ZCatalog as a good directory service for method lookups.
I think a ZCatalog would introduce way too much overhead. This lookup would happen (though not usually successfuly) with nearly every web request. For instance, any call to standard_html_header would require a lookup in the MDS, which would likely fail. With standard acquisition, the additional overhead should be largely unnoticable.
I guess the complicated question (for me, at least) is whether or not the process of acquisition could be interrupted and/or preempted for an alternate traversal means for obtaining methods either inside my Product code or in a hotfix product. The concept of method lookup doesn't seem daunting, but making it execute transparently does. I would hope something like this would be possible without modifications to the Zope core...
I think you could still use standard acquisition, just modify the namespace stack so that MDS folders are near the top all the time (or whenever you want them there).
Sean
-- | Casey Duncan | Kaivo, Inc. | cduncan@kaivo.com `------------------>
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