[Opensim-dev] Designing with reusability in mind

[Justin Clark-Casey]

Cristina Videira Lopes wrote:
> I think there's already an option for not loading up the library stuff  
> -- at least there is one in OpenSim.ini. It can load once, then ppl  
> can turn it off.
> 
> I like Adam's idea of replacing the existing Library mechanism with  
> IAR altogether. That would make it simpler. That requires the exact  
> same flexibility that I was talking about -- must pull those archiving  
> goodies out from the dungeon of Region.CoreModules...
> 
> But I shiver when I think of the spider webs, ghosts and scares that  
> the person who touches the current Library code will face..... that  
> stuff hasn't been touched since it was written.

When an IAR is loaded, assets with the same UUID already in the database are 
reused.  This approach has some weaknesses but it has the big advantage of not 
bloating the asset db.  Of course, one still has to spend the time making the 
check which may be slow on a network configuration.

I've often thought about cleaning up the inventory library code myself but never 
got around to it.  But the code ain't that complex, just needs a bit of TLR 
(tender, loving refactoring) and a dusting of unit tests :).

> 
> On Dec 9, 2009, at 4:33 PM, Melanie wrote:
> 
>> IARs also contain the assets, which would be stored to the asset
>> server again and again. On large servers, this could take ages. So,
>> I don't think IAR is a good idea, unless it's stipulated that the
>> IAR must have been made on the same server/grid, and that any assets
>> contained inside are ignored for the purpose of building the
>> library, and are assumed to be present in the asset server.
>>
>> Melanie
>>
>> Frisby, Adam wrote:
>>> Re: Library
>>>
>>> My thought was to have a directory where we can save .iar files -  
>>> and the library is built from all the IARs in that directory at  
>>> time the inventory server is started.
>>>
>>> Adam
>>>
>>>> -----Original Message-----
>>>> From: opensim-dev-bounces at lists.berlios.de [mailto:opensim-dev-
>>>> bounces at lists.berlios.de] On Behalf Of diva at metaverseink.com
>>>> Sent: Wednesday, 9 December 2009 10:39 AM
>>>> To: opensim-dev at lists.berlios.de
>>>> Subject: [Opensim-dev] Designing with reusability in mind
>>>>
>>>> In the same vein as Teravus' message about designing with
>>>> instrumentation in mind...
>>>>
>>>> I would like to ask for us to design with reusability in mind. Let's
>>>> get
>>>> out of the model that we are developing an application, and always
>>>> think
>>>> that we are developing components that can be used both for putting
>>>> together an application that looks like SL, and for other  
>>>> applications
>>>> as well.
>>>>
>>>> Case in point: in the sequence of the conversation about free IARs,
>>>> OARs, etc., I have been putting together a package with freebies. I
>>>> thought about releasing it as an IAR, like everyone else is doing,  
>>>> but
>>>> this has a problem: it requires operator access to the server -- not
>>>> all
>>>> users can take advantage of this free content.
>>>>
>>>> Solution: let's use the underused OpenSim Library and add more  
>>>> stuff in
>>>> there. No one has changed that part of OpenSim for ages! There's a  
>>>> good
>>>> reason for it: adding content to it manually is a huge PITA and
>>>> extremely error-prone. So, idea: let's take any IAR and write an
>>>> external tool that converts it into the OpenSim Library format. That
>>>> way
>>>> different operators can provide different libraries very easily:  
>>>> just
>>>> take your favorite IAR and dump it into your OpenSim Library,  
>>>> therefore
>>>> making it available to all of your users.
>>>>
>>>> This sounds easy enough. Justin has the code for unarchiving IARs...
>>>> except that it's all tangled up with Scenes. :-/
>>>>
>>>> The rule of thumb for reusability in the context of OpenSim is very
>>>> easy: the region modules that come in OpenSim.Region.CoreModules.dll
>>>> should be as thin as possible. They should only have enough meat to
>>>> bridge between Scenes and whatever it is those modules actually do.
>>>> "Whatever it is they do", for the most part, is relatively generic  
>>>> and
>>>> should be factored out into their own dll, so that it can be reused
>>>> from
>>>> elsewhere that has nothing to do with scenes. Example: all the  
>>>> service
>>>> connectors now can be reused out of the box by other tools to access
>>>> remote OpenSim servers. (OpenSim.Service.Connectors.dll)
>>>>
>>>> Counter-Example: inventory archiving/dearchiving. From looking at  
>>>> that
>>>> code, the only reason why the actual worker code needs the Scene  
>>>> object
>>>> is to be able to get to IInventoryService and IAssetService. So...  
>>>> it
>>>> should get those instead of Scene, and it should be factored out  
>>>> from
>>>> Region.CoreModules, because inventory archiving/dearchiving is a lot
>>>> more generic than a Scene utility.
>>>>
>>>> That way I could write this tool that I want in 4 hours reusing
>>>> Justin's
>>>> code as a dll, instead of having to copy-and-paste Justin's code and
>>>> purge it from all references to Scene. I would simply need to  
>>>> provide
>>>> my
>>>> own implementation of IInventoryService and IAssetService that would
>>>> write things in bin/assets and bin/inventory instead of sending  
>>>> them to
>>>> a server.
>>>>
>>>> The general request is this: let's not hide useful code under
>>>> OpenSim.Region.*, which are components that only make sense for the
>>>> live
>>>> VW server. There's so many more tools/applications that can be done
>>>> around it! -- let's not hide good code under there, where it can  
>>>> never
>>>> be reused.
>>>>
>>>> Crista / Diva
>>>>
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-- 
Justin Clark-Casey (justincc)
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