[Opensim-dev] User services refactoring status

[Tom Willans]

Thanks for this - it is a helpful clarification. I rarely mean  
criticism in a personal way so appreciate the background.

I have looked at the work involved and there is quite a lot. I  
appreciate where Mic is coming from as I have the same dilemma ( with  
even fewer resources than Intel!).


On 6 Jan 2010, at 16:10, diva at metaverseink.com wrote:

> Tom Willans wrote:
>> Are some aspects of the interface more settled than others? I  
>> appreciate
>> that this is a judgement call.
>
> Yes, some aspects are more settled than others.
> First, let me point out where this comes from, so that you and others
> can understand better.
>
> Up to recently, there was no such thing as  
> OpenSim.Services.Interfaces,
> nor the companions OpenSim.Services.Connectors and
> OpenSim.Server.Handlers. The interaction between the simulator and the
> resource services, and among the resource services themselves, was a
> mess. I don't mean it in a criticizing attitude, early-stage code is
> usually a mess. The broad stokes were there, and were really good, but
> the details were a complete mess. Simple questions like "what handlers
> are there?" or "what are the resource service interfaces?" were a
> challenge to answer, interfaces and handlers were spread all over the
> code, special cases were pervasive, classes were being used directly
> instead of interfaces, etc. The user services, in particular, were a
> nightmare, with duplication running rampant because of "standalone vs
> grid mode", and the code being on the verge of bipolar disorder.  
> Users,
> agents and avatars were being used interchangeably, with no conceptual
> distinction, misnomers everywhere, etc.
>
> This refactoring's main goal is to depart from that chaotic mess and  
> to
> instill order in the code base. It is primarily a *refactoring*,  
> meaning
> that code has moved from one namespace to another, but it is also a
> rewrite -- because in the process of revisiting the code it was clear
> that things should be done better than they were being done. In
> particular, harmful hard-coded instantiations of classes were replaced
> by dynamic loading and instantiation. The core of this is
> OpenSim.Server.Base.Utils.LoadPlugin -- this is the core of the ROBUST
> model.
>
> Having said that, let me now explain how people who plan to extend
> OpenSim should be looking at it.
>
> The main "contract" between the core code and developers of resource
> services is the collection of interfaces in  
> OpenSim.Services.Interfaces.
> This is what the simulators call, can't get around hard-coded calls to
> those interfaces. Those interfaces will stabilize very quickly. Most  
> of
> them are stable already, with the notable exception of  
> IInventoryService
> which still needs love. But all others will be stable at 0.7. Now is  
> the
> right time for people to look at those interfaces and send feedback
> about which things you think are missing.
>
> The next level of reuse is the code in OpenSim.Services.Connectors and
> OpenSim.Server.Handlers. This code is less important than the
> interfaces, because it's invisible to the simulators, therefore ppl
> should be more careful about relying on it. This is quite an important
> point that I don't think many people grasp yet, so let me explain.
>
> In most systems, the network protocols are fixed. People go to great
> lengths discussing them ad-nauseum in meetings and committees, to  
> settle
> on the right data formats, the right data, etc. NOT HERE. The network
> protocols in OpenSim are now dynamically loaded, and therefore
> replaceable. There is no such thing as *the* network protocol between
> the simulator and, say, the asset server. There can be many -- you can
> roll your own. There are reference implementations in the core
> distribution, but that's exactly what they are: reference
> implementations, they are not fixed protocols. As such, people  
> should be
> careful about relying on those reference implementations.
>
> So, to sum it up: the main contract is OpenSim.Services.Interfaces and
> those are going to be stable very soon. The level right under it,
> OpenSim.Server.Handlers and OpenSim.Services.Connectors can also be
> relied upon but it's less stable. I'm still not happy with many of
> those, so they will change after 0.7. People who don't want to put up
> with these changes may want to roll their own network protocols.
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Tom Willans
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