[Opensim-dev] Robust dynamic connector plugins...

[Justin Clark-Casey]

Hi James.  Sorry it's taken so long for me to reply, various work pressures and other stuff.

Yeah, personally I'm happy going with Mono.Addins.  As you say, we're already using it and going with the MEF would mean 
rolling a repository system.  Also, I see some talk that Mono.Addins could just use the MEF as it's underlying basis in 
the future anyway.

Now some other points.

* IRobustConnector appears to assume that all ROBUST plugins implement HTTP handlers.  However, some plugins may just 
provide extra debug console commands (some such region plugins exist already) or extend other plugins (and thus don't 
implement their own handlers).  How would these work?  This would also be a problem with IRobustConnector.Configure() 
passing back a number for the listening port.

* Why provide the option to pull down a bootstrap.ini?  This seems overcomplicated to me but perhaps an example would 
make it clearer.  And writing this data to an existing ini file makes me a bit nervous, esp. on windows since, for 
instance, the write could fail if the user also has the file open.

* I think IRobustConnector would be better named IRobustServerInConnector or similar to match XInventoryInConnector, 
GridInfoServerInConnector, etc. in OpenSim.Server.Handlers.  I like the *InConnnector because this better distinguishes 
the inbound ROBUST handlers from the simulator outbound requests (which are also called connectors and are, as we know, 
in OpenSim.Service.Connectors.

In fact, I would personally prefer to see the *InConnectors called something different to make the difference with the 
outbound connectors much clearer in the code.  However, nothing springs to mind - perhaps InConnector is good enough.

Of course, this isn't helped by the inconsistency in OpenSim.Server.Handlers naming (where most are just named 
ServerConnector).  Or the fact that these extend ServiceConnector (which implements IServiceConnector) but yet are in a 
file named ServerConnector.cs.

* From your previous e-mail, I think it would be better to start off with the specific interface for dynamic plugins and 
then look at modifying IServiceConnector once the code is in core and the implications are understood.

* I certainly think it would be good to extend such a system to region modules.  But I think there are various issues 
there which I'd prefer to discuss at a later point rather than extend this e-mail.

I also took the liberty of updating http://opensimulator.org/wiki/Feature_Proposals/PluginManager with instructions, etc.

Best,

Justin

On 27/10/12 04:11, James Hughes wrote:
> Fortis used it and it didn't seem a lot different than the way we have been using mono-addins in OpenSim.exe to this
> point. MEF uses attributes to define, as does most of addins. Some things in mono-addins still need to be defined in the
> xml manafest files, but most things can be done by attributes. MEF supports management of local assemblies and it
> doesn't provide tools for repositories and assemblies like mono-addins. Using MEF would require the additional
> development of those tools. So, the feature set of mono-addins is more complete for this type of work. We already use
> mono-addins extensively in the region server and it has served us well. It seems that some miss-steps were made in the
> implementation and need some refactoring (possibly newer versions have resolved issues that caused us to have these
> workarounds?). But, all in all we have had good results and have a great deal of the work toward managing remote
> repositories and plugins in the region server done as well. Even if we were just dealing with local assemblies I would
> see no real technical advantage to using MEF over mono-addins.
>
> The mono-addins project is part of the mono git-hub code and has been headed up by Llouis Sanchez, one of the lead Mono
> developers with Xamarin. And it is used in Monodevelop that is the IDE of their commercial products. So, its heritage is
> OK and it is actively developed.
>
> Thanks
> BlueWall
>
> On 10/26/2012 07:32 PM, Justin Clark-Casey wrote:
>> My first question is, what do you think of the alternatives to
>> Mono.Addins, chiefly MEF (Managed Extensibility Framework)? How do they
>> compare?
>>
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-- 
Justin Clark-Casey (justincc)
OSVW Consulting
http://justincc.org
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